tag:blogger.com,1999:blog-47851749438280240732024-03-12T23:33:26.915+00:00M(eta)Prolegomena to Any Future M(eta)physicsMaximehttp://www.blogger.com/profile/17820669704568697363noreply@blogger.comBlogger48125tag:blogger.com,1999:blog-4785174943828024073.post-87247725213224917632015-09-09T02:22:00.002+01:002015-09-11T22:16:25.998+01:00FilmsterOnline.com - best movie recommendations<div dir="ltr" style="text-align: left;" trbidi="on">
If you're in the mood for an excellent film that will feed your soul <a href="https://www.youtube.com/watch?v=aPxVSCfoYnU&feature=youtu.be&t=2m15s">like groceries</a>, I encourage you to have a look at Filmster's <a href="http://filmsteronline.com/">best films recommendations</a>. Whereas most other movie recommendation websites rely on <a href="https://en.wikipedia.org/wiki/Recommender_system">recommender algorithms</a> which treat you like a trepanned mononeuronal zombie sheep, Filmster trusts the world-leading cinema experts to bring you the most exciting films ever. You can browse through lists of films that have been selected and awarded at top international film festival such as Cannes, Venice, Berlin, Toronto, and at award ceremonies like the Oscars or the Césars. There are also annual top 10 lists by the legendary French review Cahiers du Cinéma, the 2012 polls conducted by the British Film Institute, and lists of famous directors' favorite films. Your days of <a href="https://vine.co/v/eTvBWrHngET">endless search </a>for high-quality films are over! Go to <a href="http://filmsteronline.com/">FilmsterOnline.com</a>.</div>
Maximehttp://www.blogger.com/profile/17820669704568697363noreply@blogger.com0tag:blogger.com,1999:blog-4785174943828024073.post-68132384770143670232015-02-14T17:20:00.002+00:002015-02-16T17:57:31.558+00:00Filmster<div dir="ltr" style="text-align: left;" trbidi="on">
I developed an app for iPhone and iPad that facilitates the search for good films on iTunes. You can learn more about it <a href="http://filmsterapp.blogspot.com/">here</a>, and download it <a href="https://itunes.apple.com/us/app/filmster/id960364538?ls=1&mt=8">here</a>.<br />
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Maximehttp://www.blogger.com/profile/17820669704568697363noreply@blogger.com0tag:blogger.com,1999:blog-4785174943828024073.post-53968394056073747512012-02-07T20:22:00.000+00:002012-02-14T09:50:20.979+00:00Derborence<div dir="ltr" style="text-align: left;" trbidi="on">
J'ai remarqué en regardant le film <i>Derborence</i> de Francis Reusser (1984) que Charles-Ferdinand Ramuz a utilisé dans son roman éponyme<i> </i>publié en 1934 une complainte du XVème siècle, celle du Roi Renaud. (<a href="http://www.site-magister.fr/chansons.htm">Apparemment</a>, Gérard de Nerval aurait publié en 1854 des <i>Chansons et Légendes du Valois</i> [sic], et le Roi Renaud était de la partie...) Il existe de multiples versions de cette chanson, mais voici celle que je connais:<br />
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<div style="text-align: center;">
<i>Quand Jean Renaud de guerre revint</i></div>
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<i>Tenant ses tripes dans ses mains,</i></div>
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<i>Sa mère à la fenêtre en haut</i></div>
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<i>Dit voici v'nir mon preux Renaud.</i></div>
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<i>Renaud, Renaud, réjouis-toi!</i></div>
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<i>Ta femme est accouchée d'un roi.</i></div>
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<i>Ni de ma femme, ni de mon fils,</i></div>
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<i>mon coeur ne peut se réjouir.</i></div>
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<i>Je sens la mort qui me transit,</i></div>
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<i>Mère faites-moi dresser un lit.</i></div>
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<i>Mais faites-le dresser si bas</i></div>
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<i>Que l'accouchée n'entende pas.</i></div>
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<i><br /></i></div>
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<i>Et quand ce fut vers la minuit</i></div>
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<i>Jean Renaud a rendu l'esprit.</i></div>
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<i><br /></i></div>
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<i>Mais dites-moi mère ma mie</i></div>
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<i>Ce que j'entends clouer ainsi?</i></div>
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<i>Ma fille c'est le charpentier</i></div>
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<i>Qui raccommode l'escalier.</i></div>
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<i><br /></i></div>
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<i>Mais dites-moi mère ma mie</i></div>
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<i>Ce que j'entends pleurer ainsi?</i></div>
<div style="text-align: center;">
<i>C'est la voisine d'à côté</i></div>
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<i>Qui a perdu son nouveau-né.</i></div>
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<i><br /></i></div>
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<i>Mais dites-moi mère ma mie</i></div>
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<i>Ce que j'entends chanter ainsi?</i></div>
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<i>Ma fille c'est la procession </i></div>
<div style="text-align: center;">
<i>Qui fait le tour de nos maisons.</i></div>
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L'enregistrement "anthropologique" (une compilation de folklore français) que j'en avais devenait ensuite inaudible, donc j'ai terminé l'histoire par moi-même (un peu à l'arrache...):<br />
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<br />
<div style="text-align: center;">
<i>Mais dites-moi mère ma mie</i></div>
<div style="text-align: center;">
<i>Qui donc ils s'en vont enterrer?</i></div>
<div style="text-align: center;">
<i>C'est Jean Renaud ton épousé</i></div>
<div style="text-align: center;">
<i>Qui a péri vers la minuit.</i></div>
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Ces paroles étaient chantées par un vieux villageois sur un ton monotone et régulier, mais on en percevait d'autant plus intensément, par contraste, la variété des divers personnages et la complexité de leurs émotions. Comme ils sont explicitement nommés, la confusion est évitée.<br />
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La version la plus proche que j'ai pu trouver, la moins édulcorée est dûe à <a href="http://www.youtube.com/watch?v=_kLKnwptvb8">Cora Vaucaire</a>.<br />
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Il y a un jeu d'écho à l'oeuvre dans ce texte. D'abord, j'ai toujours pensé que les bruits de charpenterie qu'entend la femme proviennent des clous du cercueil de son mari, mais plus haut c'est son lit qu'il recommande de construire en silence. Il se peut que ce soit en fait la même chose, le "lit" étant un euphémisme pour "lit mortuaire". Un autre dédoublement qui m'avait frappé est celle des nouveaux-nés: à la fois la femme de Renaud et la voisine viennent d'accoucher. Ca me paraissait indélicat de la part de la belle-mère d'inventer une histoire à laquelle la femme peut si bien s'identifier. Peut-être est-ce déjà une façon de lui faire sentir qu'elle est en vérité personnellement concernée par le drame qu'elle soupçonne... Une troisième résonance peut-être (en tirant un peu par les cheveux) pourrait mettre en relation l'étripage de Renaud et l'accouchement de sa femme.<br />
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Dans <i>Derborence</i>, Ramuz mélange un peu les cartes: après l'effondrement de falaise ("C'est les Diablerets qui sont venus en bas!") ce n'est pas la mort du mari que la mère tente de cacher, mais celle d'un voisin, et ce n'est pas des bruits de charpenterie qui inquiètent d'abord la femme, mais la cloche du village. Aussi, la femme est enceinte au lieu d'avoir accouché récemment. Les mensonges de la mère sur le petit de la voisine sont néanmoins bien identiques, tout comme l'incrédulité de la fille.<br />
<br /></div>Maximehttp://www.blogger.com/profile/17820669704568697363noreply@blogger.com1tag:blogger.com,1999:blog-4785174943828024073.post-16130703928993396802011-10-11T11:38:00.000+01:002011-10-13T11:05:30.934+01:00Melancholia<div dir="ltr" style="text-align: left;" trbidi="on">
Si on définit la mélancolie comme une inaptitude au bonheur, on peut imaginer reconstruire grossièrement le processus qu'a suivi Lars von Trier pour écrire le scénario de son dernier film <i>Melancholia</i>. Il lui fallait d'abord poser comme cadre un événement qui se prête pleinement au bonheur -- un mariage fastueux, un avenir professionnel radieux, etc. -- pour mieux faire ressortir le caractère (apparemment) abbérant des sentiments d'abatement de la mariée Justine (Kirsten Dunst, prix d'interprétation féminine à Cannes, même si c'est plutôt Charlotte Gainsbourg qu'on regarde.. mais bon elle l'avait déjà pécho en 2009 pour sa prestation dans <i>Antichrist</i>). Sa froideur et son détachement incompréhensibles finissent par faire capoter le mariage et partir le marié.<br />
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La deuxième partie du film décrit les quelques jours précédant la collision d'une planète nommée Melancholia qui se cachait jusque-là derrière le Soleil. J'y vois une variation sur le même thème d'un bonheur à portée de main (une jolie famille dans une belle propriété, un événement astronomique unique et excitant à observer, etc.) qui périclite malgré tout. La destruction de la vie sur Terre (et donc partout selon Justine) qui s'ensuit est l'image amplifiée de la séparation des mariés qui les prive de leur chance de progéniture. C'est donc la même histoire qui est racontée de deux manières différentes: la première fois à un niveau personnel, famillial, et la seconde à un niveau cosmologique. Une telle projection de motifs psychologiques sur des éléments naturels me fait penser à la manière dont les alchimistes projetaient leurs conflits internes sur les métaux. Jung disait que l'alchimie constituait le revers de la médaille du christianisme en ce sens qu'alors que les chrétiens se considéraient comme pécheurs originels et cherchaient à se sauver par la foi, les alchimistes considéraient que c'était la matière physique qui était corrompue et voulaient la purifier en transformant par exemple le plomb en or (philosophique).<br />
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Peut-être Lars a-t-il été influencé par la lecture de <i>Saturne et la Mélancolie</i> de Panofsky et Saxl?<br />
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<br /></div>Maximehttp://www.blogger.com/profile/17820669704568697363noreply@blogger.com0tag:blogger.com,1999:blog-4785174943828024073.post-43488535285907365932011-09-17T18:27:00.004+01:002011-09-20T00:37:11.033+01:00WoW for science<div dir="ltr" style="text-align: left;" trbidi="on">
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<a href="http://eu.media.blizzard.com/wow/media/screenshots/screenshot-of-the-day/classic/classic-ss98-large.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="255" src="http://eu.media.blizzard.com/wow/media/screenshots/screenshot-of-the-day/classic/classic-ss98-large.jpg" width="320" /></a></div>
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I found this <a href="http://www.youtube.com/watch?v=dE1DuBesGYM&feature=player_embedded#!">talk</a> by Jane McGonigal on the benefits of gaming quite inspiring (see also a <a href="http://playtime.blog.lemonde.fr/2011/09/17/le-jeu-video-peut-il-changer-le-monde/">more recent one</a>). She makes a convincing point that after having spent about 10,000 hours playing online games during their youth (almost as much as they spend in school) gamers have acquired <i>mad skillz</i> and it would be nice to see this potential realize itself in the real world. She refers to the game "World of Warcraft" (WoW) as the "ideal collaborative problem-solving environment" (4:30) and I immediately thought this kind of platform should be used for scientific research. This would basically turn research into video game. Note that this isn't a very long stretch since the feeling of research can be as <a href="http://www.arte.tv/fr/science/Paroles-de-chercheur/Marc-Lachieze-Rey-/1212194.html">exciting</a> as that of video game.<br />
I have to say though that I don't know the first thing about WoW, except that you have to "<a href="http://www.youtube.com/watch?v=AY5tM_U5VVw">pwn the noobs</a>" and become a "leet king" (1337). Apparently, you are being assigned a mission matching the abilities of your avatar (orcs, trolls, dwarfs, paladin, etc.), and you collaborate with hundreds of other players to achieve an "epic win". You get frequent feedback on your performance and your level increases.<br />
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Now imagine that instead of having to kill a dragon or whatever, the players are given actual unsolved scientific problems. Pretty cool, hu?<br />
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In fact, similar platforms already exists, most notably Tim Gowers' <a href="http://en.wikipedia.org/wiki/Timothy_Gowers#Polymath_Project">Polymath</a> project, and it's also interesting to recall that in their early days the internet and the world wide web were inextricably linked to scientific research. The <a href="http://arxiv.org/abs/1108.2700">arXiv</a> is a brilliant example. This all comes together in <a href="http://michaelnielsen.org/blog/">Michael Nielsen</a>'s promotion of <a href="http://michaelnielsen.org/blog/open-science-2/">open science</a>. [Btw, all those TeD talks are so insufferably optimistic and well-intentioned!]<br />
Maybe another site worth mentioning would be the <a href="http://garden.irmacs.sfu.ca/?q=purpose">Open Problem Garden</a>.<br />
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That's more like a collection of hyperlinks than a proper reflection, but I'll leave it at that for now.<br />
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Maximehttp://www.blogger.com/profile/17820669704568697363noreply@blogger.com0tag:blogger.com,1999:blog-4785174943828024073.post-46499277747104813102011-01-17T23:23:00.011+00:002011-01-26T12:16:40.715+00:00Uncle Boonmee Who Can Recall His Past Lives<a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgzbkRkn6Q8Jj_Nf6phjF9BzApq6dyRl0s_LdyQOl6AZ6QgdYTVjwEdQWWvGCsA9M-HIVV6M7usJv85jpvuIflAU0HGAJh5Tevh1X4eXg7yryRIKW5bXficHauFpvGcErUXMLip2rWH5dIc/s1600/uncle-boonmee-3_420.jpg"><img style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;width: 320px; height: 200px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgzbkRkn6Q8Jj_Nf6phjF9BzApq6dyRl0s_LdyQOl6AZ6QgdYTVjwEdQWWvGCsA9M-HIVV6M7usJv85jpvuIflAU0HGAJh5Tevh1X4eXg7yryRIKW5bXficHauFpvGcErUXMLip2rWH5dIc/s320/uncle-boonmee-3_420.jpg" border="0" alt="" id="BLOGGER_PHOTO_ID_5563310376344813474" /></a><div style="text-align: left;"><br /></div><div>The 2010 <i>Palme d'Or</i> finally arrived in Oxford. It was at the Ultimate Picture Palace, I was sitting on the very first row, and I had the time of my life. It's a sublime jewel of supernatural enchantments, simple and sophisticated altogether, traditional and avant-garde. Well done Apichatpong Weerasethakul!</div><div><br /></div><div>I just want to talk about one single shot, not because it is the most representative of the movie, but because it struck my imagination. It's a static shot of a room, facing a wall against which there is a bench on which two persons are sitting. They are watching a tv on a table against the left wall of the room. So they are not facing the tv but rather have a very oblique perspective on it. So much so that I wondered if they were actually able to see the screen. It seems completely unrealistic. A more conventional way to edit such a scene would have been to show the people frontally and then cut on a shot of the tv that they're watching (btw the last scene of the movie is of that type:(. Then I realized that it did not matter after all, since the scene makes perfect narrative sense as it is. It's clear that they're watching the tv, even though both their faces and the tv are visible simultaneously. This stylistic effect is somehow reminiscent of certain cubist paintings which show a face both in profile and frontally. But it goes even further: whereas the cubist portrait presents different perspectives on one object, Apichatpong's shot encompasses both the observers and what they observe at once. Some sort of primordial unity regained!</div><div><br /></div><div><span class="Apple-style-span" style="color: rgb(0, 0, 238); -webkit-text-decorations-in-effect: underline; "></span></div><div style="text-align: center;"><span class="Apple-style-span" style="color: rgb(0, 0, 238); -webkit-text-decorations-in-effect: underline; "><img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjYEuD3wESqlOMMrMZT3BULq_Zy2scLKEF0K53PdMVauuMKRrDnbBIozJYrYM9LwwiFLtzS8fBujOwyeZIGjHdx6oo-X_n4zxc_QV4ptNdpRAQBsYNWcKuK7AikXplxlhfdGuyKoSIMAdKL/s320/Dora+Maar.jpg" border="0" alt="" id="BLOGGER_PHOTO_ID_5563307987130625890" style="display: block; margin-top: 0px; margin-right: auto; margin-bottom: 10px; margin-left: auto; text-align: center; cursor: pointer; width: 255px; height: 320px; " /></span></div>Maximehttp://www.blogger.com/profile/17820669704568697363noreply@blogger.com0tag:blogger.com,1999:blog-4785174943828024073.post-53109584830551762011-01-14T22:55:00.020+00:002011-01-16T01:48:24.636+00:00Googoo Gaga<div style="text-align: center;"><br /></div><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhfPdZ1avc40cd0_SFKNPGqCpeogHCuGBmnLTTOq8lHc5xumxDuAtwcwAsHuBsJoOTHPBXxjUtBEDqeUMHGstqUersCdlunqeRKOFXv7uSjgzCihGdg3zMjb8t5q3XZ4sJL-NicSfcEzi_0/s1600/lady-gaga2.jpg"></a><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgiIrtQtj_fXt6kMYt2sOUdBbVefP5b_m6LAGpelQuy4a9Mh-xSI-KlhXjVyPGPPXH8C_zW8iXoSjZMTmabFSaI81FE4hF1GvTbJtyaMcwcAIaA_y2xoEvM0O28UV2oDsY26SB-iKNxMnJT/s1600/lady-gaga.jpg"><img style="float:right; margin:0 0 10px 10px;cursor:pointer; cursor:hand;width: 217px; height: 320px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgiIrtQtj_fXt6kMYt2sOUdBbVefP5b_m6LAGpelQuy4a9Mh-xSI-KlhXjVyPGPPXH8C_zW8iXoSjZMTmabFSaI81FE4hF1GvTbJtyaMcwcAIaA_y2xoEvM0O28UV2oDsY26SB-iKNxMnJT/s320/lady-gaga.jpg" border="0" alt="" id="BLOGGER_PHOTO_ID_5562571423756306274" /></a><div><div><div><div><div>I've been willing to write about Lady Gaga for a little while, but it was incompatible with postdoc application time so I postponed. Also, I wasn't too sure, to be honest, what I could possibly write about her that would not be too obviously dumb. My attention was brought to her by <a href="http://www.youtube.com/watch?v=cvGWr-Ggg-g">this video</a> (not exactly the official vid -- careful). Check out <a href="http://www.youtube.com/watch?v=qrO4YZeyl0I&feature=related">this video rather</a>, viewed more than 300m times (I remember a time where a million views was amazing..) [I'm not saying there's nothing lame about the video btw]. I liked the fact that some of the lyrics are in French, or at least in some sort of French. Quite glam I thought, for an American pop song. Also there's a purer rave sound than you'd expect, stuff that was underground in the 90s but that still does the job OK. Then I realized that Lady Gaga is closer to a performance artist than a pop star, and a rather interesting one moreover. My first suspicion of her significance was confirmed when I learned that the young US officer that smuggled the 240,000 diplomatic cables published by Wikileaks did so by burning them on a Lady Gaga CD! This mixture of art and political revelations might appear coincidental but I like to imagine, a bit in the spirit of Wreck & Salvage, that there is some deeper connections, whose roots dive into the current American Zeitgeist. Whatever.</div><div><div><br /></div><div>Gaga's first words in <i>Bad Romance</i> are something like</div><div><br /></div><div><blockquote><i><b>Rha rha a ah aha<br /></b></i><div><i><b>Roma rromama a</b></i></div><div><i><b>Gaga oh lala a</b></i></div><div><i><b>Want your bad romance</b></i></div></blockquote><div></div><div><br /></div><div>[Just to mention, there are already two French elements in there: the rolled "r" and the "oh lala".]</div><div><br /></div><div>And this is the kind of thing that will play in your head while you're cooking for instance. So at some point I asked myself but what is she saying for fuck's sake? There are words that I can recognize, specially the last bit, that's rather clear, and "Gaga" also makes an apparition, and there are bits that are clearly just sounds, like the "ohooho" of the introduction; but what I find puzzling is that there is also something that is between the two.</div><div><br /></div><div>First, the "rha rha" are purely bestial (think <a href="http://www.youtube.com/watch?v=3mqVvEaQefk">MGM lion</a>) and they degenerate, just like every line, to some simply musical sounds. Then comes the intriguing part: "Roma". This also appears as just a meaningless sound but it's far too close [<i>sic</i>] to the "romance" in the title of the song not to be related to it. Certainly it has to be some embryonic version of it. Something is taking shape here, from the bestiality of a prelinguistic realm towards some more advanced form of communication, namely language. Notice also that when the "roma" degenerates, one could hear "mama" [compare to "papa <a href="http://www.youtube.com/watch?v=l3R3KqrJAI4">paparazzi</a>"]. Just like what happens in the development of a child, the first thing that comes out of the undefined darkness is the figure of the mother. Then comes "Gaga", the ego. This also frequently a child's first sounds. And finally something resembling a sentence expressing a desire towards the other can be formulated.</div><div><br /></div><div>So my verdict would be that this chorus illustrates the genetics of the artistic process, through which a raw emotion is sublimed into some creation that resort to a higher level language.<br /><div><br /></div><div>Now one could wonder if this emergence process was successfully performed in this case. After all, it all comes to wanting "your <i>bad</i> romance". Sounds more like a destructive drive to me. In addition, the ego/other or subject/object couple is not adequately articulated. Not only is the "I" still missing, but also it would seem more natural to want "<i>our</i> romance" instead of "yours". Similarly, later in the song one hears "And I want your revenge": what is that suppose to mean? Well, maybe this is intended as "I want <i>my</i> revenge on you". That would make more sense. Unless... Could the artist be skillfully using this me/you confusion to underline the fact that such a vicious spiral of projections and counter-projections often characterizes a "bad romance"? Stefani Germanotta: brava!</div></div></div></div></div></div></div></div><div><br /></div><div><span class="Apple-style-span" style="color: rgb(0, 0, 238); -webkit-text-decorations-in-effect: underline; "><img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhfPdZ1avc40cd0_SFKNPGqCpeogHCuGBmnLTTOq8lHc5xumxDuAtwcwAsHuBsJoOTHPBXxjUtBEDqeUMHGstqUersCdlunqeRKOFXv7uSjgzCihGdg3zMjb8t5q3XZ4sJL-NicSfcEzi_0/s320/lady-gaga2.jpg" border="0" alt="" id="BLOGGER_PHOTO_ID_5562572242567994114" style="display: block; margin-top: 0px; margin-right: auto; margin-bottom: 10px; margin-left: auto; text-align: center; cursor: pointer; width: 320px; height: 240px; " /></span></div>Maximehttp://www.blogger.com/profile/17820669704568697363noreply@blogger.com2tag:blogger.com,1999:blog-4785174943828024073.post-6613487394988846432010-09-05T15:11:00.029+01:002010-09-06T10:55:13.072+01:00Early thoughtsI have a rather clear memory of what might have been the first time I realised that I was capable of thinking. We were having a lunch with my family in the annex of our house, where we used to roast meat on Sundays. The conversation came to the subject of the existence of God, and whether it was possible to prove it or not. I said that I considered that such a proof was not even desirable since since according to Saint Paul's <i>Apocalypse</i> God would come back on Earth at the end of time if we managed by earthly considerations to prove that He's here, then that would be the end of time. My parents' and sister's reaction was that of surprise that such ideas could circulate in my head. This made me aware that a thought had been created within me that had not been introduced there from the outside.<div><br /></div><div>Some years (?) later I came across Saint Anselme of Canterbury's "ontological argument" for the existence of God. Roughly, it resorted to the <i>reductio ad absurdum</i> and said that given that the Perfect Being must have all positive qualities, if He didn't exist, He would lack one of those qualities, namely the quality of existing. I imagined a refutation of it, which went as follows. If the existence of God could be proven, then we humans would have no choice but to believe in Him -- in which case He would also lack a quality, the generosity of letting His creatures decide freely if they want to believe in Him or not.</div><div><br /></div><div>Beyond the naive scholasticism of those early thoughts, something in their spirit is still very much akin to what turns me on nowadays.</div><div><br /></div><div>Had I pushed my reflections a bit further, I would have realised that I was dealing with an absurd absurdity. By the same type of reasoning it has to be true that God does exist but it must also be impossible for us to prove it. How can this be? And then of course it's Godel's incompleteness theorem that comes to mind. (Godel who btw wrote down an <a href="http://en.wikipedia.org/wiki/G%C3%B6del%27s_ontological_proof">ontological proof</a> of his own using modal logic, which he kept secret until he thought his last days had arrived...)</div><div><br /></div><div><br /></div><div>PS: Those memories came back to me today while I was playing with the following thought:</div><div><blockquote>"The meaning of life is to search for the meaning of life."</blockquote>I like it because of its circularity and because it's contradictory in the sense that it implies that were we to actually find the meaning of life it would be gone. In fact it's also contradictory in the sense that it undermines its own content: it gives you the meaning so why search for it? The entire substance of the sentence is sucked in by the word "search", which then operates just like a minus sign in an equation. One could for example symbolise it abstractly as<br /><br />\[ \infty - \infty = 0.\]<br /><br /></div><div>I fancy writing it in <a href="http://en.wikipedia.org/wiki/Rose_is_a_rose_is_a_rose_is_a_rose">repetitive</a> style as well:</div><div><blockquote style="text-align: justify;"> " The meaning of life </blockquote><blockquote style="text-align: justify;">is to search for the meaning of life </blockquote><blockquote style="text-align: justify;">is to search for the meaning of life </blockquote><blockquote style="text-align: justify;">is to search for the meaning of life."</blockquote></div><div>Just like that.</div><div><br /></div><div>PPS: the etymology of the word "search" is agreeable since, along with <i>chercher</i> in French and <i>cercare</i> in Italian, it comes from the Latin word <i>circus</i>, the circle. :) Should we push the perversity yet another step further and replace it by the word "research"?</div>Maximehttp://www.blogger.com/profile/17820669704568697363noreply@blogger.com2tag:blogger.com,1999:blog-4785174943828024073.post-25529193073845501692010-07-05T18:37:00.006+01:002010-07-05T23:39:46.917+01:00Laughing and researchWhat is it that makes us laugh in a joke, after all?<br />It seems to me that a joke always requires from the audience a certain amount of mental effort to see the meaning of the joke. There is a gap in the plot and it has to be filled for the joke to be funny.<br />For <a href="http://www.youtube.com/watch?v=0tAH4UYxrlw">instance</a>:<br /><br /><blockquote>A guy comes into a bar, completely drunk, and asks for a drink. The barman tells him that he never serves drunk people. The guy goes away but comes back five minutes later. The barman refuses again. The guy goes away but comes back ten minutes later, and so on.<br />Finally the drunk guy asks the barman: "Is there a single bar in this city where you <span style="font-weight: bold;">don't</span> work?"</blockquote><br />To laugh at this joke you need to understand that the guy thinks he is visiting different bars, but he is so drunk he always ends up in the same bar.<br /><br />The misanthropically inclined mind will think that then the laughter is only a demonstration of pride to have been able to crack the mystery.<br /><br />But another interpretation would be that cracking the mystery is a pleasure in itself, and the real cause of the laughter.<br /><br />We researchers are devoting our time to crack mysteries, although of different proportions. We are laughing the great laughter.Maximehttp://www.blogger.com/profile/17820669704568697363noreply@blogger.com1tag:blogger.com,1999:blog-4785174943828024073.post-49643084685601298182010-03-21T18:39:00.011+00:002010-04-18T00:41:14.806+01:00The geometry of 3-manifolds<div style="text-align: left;">If you want to get an idea of the famous Poincaré conjecture for which Grigoriy Perelman was recently awarded a <a href="http://www.claymath.org/">Millenium prize</a>, I highly recommend watching this very entertaining <a href="http://athome.harvard.edu/threemanifolds/index.html">lecture</a> by Curtis McMullen at Harvard in 2006.</div><div><br /></div><div>I had never realised that tori of genus greater than one are hyperbolic! It makes sense, if you think that a sphere (genus 0) has positive curvature, a torus (genus 1) is flat, that tori of genus 2 and more have negative curvature. These higher tori can be constructed by gluing together the edges of polygons.</div><div><br /></div><div>I wonder whether anti-de Sitter space can also be viewed as a high genus space. Are the many black holes in the universe implying that it has a high "genus"? But the notion of genus isn't clear in higher dimensions...</div><div><br /></div><div>So I started (very naively) to think about black holes on a latex surface, like the ones shown in the lecture. Consider a sphere and put a stone at the north pole. The sphere will bend, just like spacetime bends around the sun. Now imagine that you had a way to increase the mass of the stone, it would create a well at the north pole which would eventually touch the south pole from the inside. What happens then? The well could continue to become deeper and deeper but now it would create a spike out of the south pole. This is certainly misleading. More likely, once the stone approaches the south pole from the inside, its mass sucks it in, creating a well (as well).</div><div><br /></div><div>Ultimately, what you'll end up with is a torus. The Planckian mass is at the centre of this torus, where there is really no spacetime: that's the black hole!</div><div><br /></div><div><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhflvFNhHhIG5ILhNAtKS8oTrDdJHKrt7h6aRMG9IZ0N5ZxwYZBreQDsRORHqdOX7Q-HdBOvAhHc5ka36KEW4IIE_JTQnzjHTJI99r2Dlz9ojFM7fmk1fdyLVFylQgN5maQvQhEZ98dtnXU/s1600/S2toT2.jpg"><img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhflvFNhHhIG5ILhNAtKS8oTrDdJHKrt7h6aRMG9IZ0N5ZxwYZBreQDsRORHqdOX7Q-HdBOvAhHc5ka36KEW4IIE_JTQnzjHTJI99r2Dlz9ojFM7fmk1fdyLVFylQgN5maQvQhEZ98dtnXU/s400/S2toT2.jpg" border="0" alt="" id="BLOGGER_PHOTO_ID_5452695139239832098" style="display: block; margin-top: 0px; margin-right: auto; margin-bottom: 10px; margin-left: auto; text-align: center; cursor: pointer; width: 400px; height: 128px; " /></a></div><div>I had an unexpected confirmation of this picture in my kitchen. There was a frying pan full of a layer of greasy water and I noticed that it tended to leave discs where there was no water. By slowly pouring more water into the pan, the discs would shrink until there reach zero size, at which point a circular wave was emitted. I had just witnessed a topology change;) I could also reverse the process by taking some water out of the pan and stirring up the water. When the water had stabilised enough, discs were suddenly appearing and expanding quickly. That's my version of frying pan black holes: try it at home!</div><div><br /></div><div>PS: the key is the circular wave.</div>Maximehttp://www.blogger.com/profile/17820669704568697363noreply@blogger.com0tag:blogger.com,1999:blog-4785174943828024073.post-56961576523045734512010-02-15T20:15:00.009+00:002010-02-16T11:17:39.565+00:00"Holographic Superconductos in M-theory"Last Monday we had <a href="http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=f+a+gauntlett+and+t+supercond%23&FORMAT=WWW&SEQUENCE=">Jerome Gauntlett</a> telling us about exciting applications of the AdS/CFT correspondence to Condensed Matter systems.<br /><br />Some quantum critical points (second order phase transitions) are at strong coupling, and hence intractable with standard CM technics, but the AdS/CFT comes to the rescue. This happens for example for "heavy fermions" (quasi-particles condensing to give Cooper pairs) or for high $T_c$ cuprates that have a superconducting phase. Holographic descriptions of such systems have been put forth by <a href="http://arxiv.org/abs/0801.2977">Gubser</a> and by <a href="http://arxiv.org/abs/0803.3295">Hartnoll, Herzog, and Horowitz</a>. The strongly coupled CFT in 3d has a holographic AdS dual, which has a $U(1)$ gauge symmetry that can be spontaneously broken by a charged field $\chi$. A finite temperature the description is in terms of a black hole in AdS, and it acquires charged hair at low temperature that breaks the $U(1)$.<br /><br />Almost all the work on this topic has been taking a "bottom up" approach, but Jerome took the "top down" approach: constructing holographic superconductors from M-theory using consistent Kaluza-Klein truncation with Sasaki-Einstein spaces. Here consistent truncation means that you can keep only a finite set of the light KK fields (you cut the infinite KK towers) but then any solution of the low dimensional theory involving those remaining fields has to uplift to an <i>exact</i> solution of the original higher dimensional theory. So consider a stack of M2-branes at the tip of a Calabi-Yau cone on a Sasaki-Einstein seven-manifold for which the near-horizon limit is $AdS_4 \times SE_7$ with metric \[ d s^2 = \frac{1}{4} d s^2 (AdS_4) + d s^2 (SE_7) \] with \[ d s^2 (SE_7) = d s^2 (KE_6) + \eta \otimes \eta~,\] where $\eta$is the contact form. There is an associated Killing vector, which (although it does not always have to close) generates the required $U(1)$ symmetry. The four-form field strength is $G_4 = \frac{3}{8} \text{Vol}(AdS_4)$. This geometry is dual to $\mathcal{N} =3$ SCFTs in $d=3$ (or $\mathcal{N} = 8$ if $SE_7$ is replaced by a seven-sphere).<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh9hSQ3doW3N4bii8LZyKSN8QFjaoEGgtoMlXtOxAYfUc8Pkz2FSm4x6VomBcoGgQNqSAsBnYqGmbxY2cEAq3P0d3vIRT8Rb8GVnvsyDrdaxdEVd3eTbvuDYgSAgQunM6n6XgtzlqCh2ph_/s1600-h/Slide1.jpg"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 400px; height: 300px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh9hSQ3doW3N4bii8LZyKSN8QFjaoEGgtoMlXtOxAYfUc8Pkz2FSm4x6VomBcoGgQNqSAsBnYqGmbxY2cEAq3P0d3vIRT8Rb8GVnvsyDrdaxdEVd3eTbvuDYgSAgQunM6n6XgtzlqCh2ph_/s400/Slide1.jpg" alt="" id="BLOGGER_PHOTO_ID_5438585457941040754" border="0" /></a>Now, had the membranes been replaced by anti-membranes, $G_4$ would have the opposite sign but more importantly the dual SCFTs would have $\mathcal{N}=0$. The corresponding geometry is called skew-whiffed $AdS_4 \times SE_7$. It is this geometry that can reproduce and generalize the HHH models. The consistent truncation found by Jerome has an extra neutral scalar field $h$ which corresponds to a deformation of the skew-whiffed CFT by an operator $\mathcal{O}_h$. At low temperature this system exhibits a superconducting phase.<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiM94xsPglFNff1JX6-dnuF1hJqint1RT439IpW5EDAc3Tbi2qomAE6AiWIfruhFU74DOl-Zmx9zUcc2sYEkval7dRDkmIt9R33sYV1-B44-kMKWZtnevKY1_kZRzI6qY2NLHIxLeMYSb7n/s1600-h/Slide1.jpg"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 374px; height: 280px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiM94xsPglFNff1JX6-dnuF1hJqint1RT439IpW5EDAc3Tbi2qomAE6AiWIfruhFU74DOl-Zmx9zUcc2sYEkval7dRDkmIt9R33sYV1-B44-kMKWZtnevKY1_kZRzI6qY2NLHIxLeMYSb7n/s400/Slide1.jpg" alt="" id="BLOGGER_PHOTO_ID_5438582770825073794" border="0" /></a>Jerome concluded by suggesting that if superconductivity had not already been discovered, such a study would have pointed it out to us. M-theory might thus lead to a similarly radical discovery of qualitatively new phenomena...Maximehttp://www.blogger.com/profile/17820669704568697363noreply@blogger.com0tag:blogger.com,1999:blog-4785174943828024073.post-39700726818069811772010-01-24T23:17:00.006+00:002010-04-18T00:44:20.019+01:00David BlaineI watched this TeD video where the magician David Blaine explains how he broke the Guiness record of apnea by staying a little more than 17 minutes under water.<br /><!--copy and paste--><object width="446" height="326"><param name="movie" value="http://video.ted.com/assets/player/swf/EmbedPlayer.swf"><param name="allowFullScreen" value="true"><param name="wmode" value="transparent"><param name="bgColor" value="#ffffff"> <param name="flashvars" value="vu=http://video.ted.com/talks/dynamic/DavidBlaine_2009P-medium.flv&su=http://images.ted.com/images/ted/tedindex/embed-posters/DavidBlaine-2009P.embed_thumbnail.jpg&vw=432&vh=240&ap=0&ti=741&introDuration=16500&adDuration=4000&postAdDuration=2000&adKeys=talk=david_blaine_how_i_held_my_breath_for_17_min;year=2009;theme=new_on_ted_com;theme=medicine_without_borders;theme=to_boldly_go;event=TEDMED+2009;&preAdTag=tconf.ted/embed;tile=1;sz=512x288;"><embed src="http://video.ted.com/assets/player/swf/EmbedPlayer.swf" pluginspace="http://www.macromedia.com/go/getflashplayer" type="application/x-shockwave-flash" wmode="transparent" bgcolor="#ffffff" width="446" height="326" allowfullscreen="true" flashvars="vu=http://video.ted.com/talks/dynamic/DavidBlaine_2009P-medium.flv&su=http://images.ted.com/images/ted/tedindex/embed-posters/DavidBlaine-2009P.embed_thumbnail.jpg&vw=432&vh=240&ap=0&ti=741&introDuration=16500&adDuration=4000&postAdDuration=2000&adKeys=talk=david_blaine_how_i_held_my_breath_for_17_min;year=2009;theme=new_on_ted_com;theme=medicine_without_borders;theme=to_boldly_go;event=TEDMED+2009;"></embed></object><br /><div>To me, this guy is more than a magician, and more than an athlete, he's a pure artist. His determination to push the human body beyond its clinical limits is of course very spectacular and impressive, but it also says something about what it means to live. How much can one deprave the body from resources (food, oxygen) and still survive? There is also a sense of askesis very similar to what one can find in several religious traditions (fast, meditation, etc.)...</div><div><br /></div><div>However, what struck me particularly was the fact that after a failed attempt he finally broke the record (live on TV) when he was convinced that he had no chance to succeed since his heartbeat was unusually high during the immersion. I think there might be some universal truth in this: great things are often achieved just at the moment when a long chain of intense efforts oriented to a precise goal ultimately gives way to the disappearance of all hope.</div><div><br /></div>Maximehttp://www.blogger.com/profile/17820669704568697363noreply@blogger.com1tag:blogger.com,1999:blog-4785174943828024073.post-21540020271546180602009-11-26T00:21:00.001+00:002009-11-26T00:22:41.401+00:00Nirmali<a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgYXqMlEy6Wet8e98EG8qJvrDTqbVTHzjiH1WoI5PgwjkKcpr5guY0iYch8Zsdz2jgdAhlN1vTC-8QeZfEC38eHeWJlcScU96PVgOpI_rZoz_MYMSiuIYoEMryf7DPEwM9igh5z28JYixei/s1600/forest.jpg"><img style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;width: 153px; height: 400px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgYXqMlEy6Wet8e98EG8qJvrDTqbVTHzjiH1WoI5PgwjkKcpr5guY0iYch8Zsdz2jgdAhlN1vTC-8QeZfEC38eHeWJlcScU96PVgOpI_rZoz_MYMSiuIYoEMryf7DPEwM9igh5z28JYixei/s400/forest.jpg" border="0" alt="" id="BLOGGER_PHOTO_ID_5408201132250976098" /></a>Maximehttp://www.blogger.com/profile/17820669704568697363noreply@blogger.com0tag:blogger.com,1999:blog-4785174943828024073.post-44062034620237414112009-11-05T00:08:00.005+00:002010-04-18T00:47:20.146+01:00II. The twofold task in working out the question of Being. Method and design of our investigationThis is a summary of Heidegger's second introduction to Being and Time.<div><br /></div><div><i>5. The ontological analytic of Dasein as laying bare of the horizon for an interpretation of the meaning of Being in general.</i></div><div><br /></div><div>Dasein is a tricky thing to analyse in that it is in some respect obvious to us and in some other obscure. MH writes that "Dasein is ontically 'closest' to itself and ontologically farthest; but pre-ontologically it is surely not a stranger." As regard to its existence, we understand it immediately since "we <i>are</i> it". But "in spite of this, or rather for just this reason", it is the most difficult thing to really understand in its essence, because we are naturally inclined to consider it as obvious, self-evident. However, intuitively we have some sort of embryonic understanding of its essence since "Dasein <i>is</i> in such a way as to be something which understands something like Being". To perform an analytic of Dasein we must "choose such a way of access and such a kind of interpretation that this entity can show itself in itself and from itself".</div><div><br /></div><div>MH announces that "we shall point to temporality as the meaning of the Being of that entity which we call "Dasein"," and that "we shall show that whenever Dasein tacitly understands and interprets something like Being, it does so with time as its standpoint". And in consequence, "time needs to be explicated primordially as the horizon for the understanding of Being, and in terms of temporality as the Being of Dasein, which understands Being." But the conception of time required will have to depart from the ordinary understanding of time (in particular time as a "criterion for naively discriminating various realms of entities", such as temporal, non-temporal, 'supra-temporal' eternal entities...).</div><div><br /></div><div>"<i>The central problematic of all ontology is rooted in the phenomenon of time, if rightly seen and rightly explained</i>".</div><div><br /></div><div><i>6. The task of destroying the history of ontology</i></div><div><br /></div><div>Dasein's own past "is not something which <i>follows along after</i> Dasein, but something which already goes ahead of it" (Dasein "<i>is</i> its past"). This has the perverse effect that Dasein "falls prey to the tradition of which it has more or less explicitly taken hold. This tradition keeps him from providing its own guidance, whether inquiring or in choosing". And this also holds true for ontological understanding. Tradition "becomes master" and conceals itself. "It blocks our access to those primordial 'sources' from which the categories and concepts handed down to us have been in part quire genuinely drawn". The Greek ontology has thus "deteriorated to a tradition in which it gets reduced to something self-evident". Then "in the Middle Ages this uprooted Greek ontology became a fixed body of doctrine". Subsequent concepts such as "the <i>ego cogito</i> of Descartes, the subject, the "I", reason, spirit, person" (...) "all remain uninterrogated as to their Being". Just like in certain oriental philosophies, the primordial clarity of mind has deteriorated throughout history into rigidified clichés.</div><div><br /></div><div>Our task is clear: "we are to <i>destroy</i> the traditional content of ancient ontology". AC/DC man! But nihilist enthusiasm is inappropriate: this destruction is "far from having the <i>negative</i> sense of shaking off the ontological tradition" (or "bury the past in nullity"). "We must, on the contrary, stake out the positive possibilities of that tradition, and this always means keeping it within its limits". </div><div><br /></div><div>The point of departure for the task of destroying the problematic of Temporality will be the Kantian doctrine of time. After all, Kant is "the first and only person who has gone any stretch of the way towards investigating the dimension of Temporality". Still he didn't go very far because he "took over Descartes' position quite dogmatically". And Descartes, with his radical discovery of the '<i>cogito sum</i>', left undetermined the meaning of the Being of the '<i>sum</i>'. He "is 'dependent' upon medieval scholasticism". Furthermore, "Kant's basic ontological orientation remains that of the Greeks", and more precisely that of Aristotle.</div><div><br /></div><div>In summary, the strategy is clear: in order to concretely address the question of Being with time as a horizon we must first destroy the associated tradition "until we arrive at those primordial experiences in which we achieved our first ways of determining the nature of Being".</div><div><br /></div><div>7. The phenomenological method of investigation</div><div><br /></div><div><br /></div><div><br /></div>Maximehttp://www.blogger.com/profile/17820669704568697363noreply@blogger.com0tag:blogger.com,1999:blog-4785174943828024073.post-45951621656852233812009-10-28T15:57:00.014+00:002009-10-31T18:41:44.395+00:00"AdS/CFT from F-theory?"At the lunch group meeting James told us about a fairly recent paper by Polchinski and Silverstein, entitled <a href="http://arxiv.org/abs/0908.0756">Dual Purpose Landscaping Tools: Small Extra Dimensions in AdS/CFT</a>. Their goal is to construct vacua of string or M-theory with minimal supersymmetry of the form $AdS_d \times \text{small}$, where small means that the internal space is small compared to the AdS radius. The problem is that in the case of the standard Freund-Rubin backgrounds (whose dual CFTs are rather well understood in terms of the near-horizon limit of D3- or M2-branes at the tip of a Calabi-Yau cone), the radius of the internal space is of the same size as the AdS radius.<br /><br />The new idea is to add some D7-branes. These contribute to the potential energy with an opposite sign to the curvature of the internal manifold, and so could be chosen such that the resulting cosmological constant is small.<br /><br />This is where F-theory comes into play. The construction there is to glue IIB solutions using the $SL(2,\mathbb{Z})$ duality symmetry, and to allow for D7-branes. A D7-brane, which is codimension two and thus can be surrounded by a circle, is a unit magnetic source for the axion $C_0$ (a periodic RR scalar field): \[\int_{S^1} d C_0 =1~.\] The axion combines with the dilaton $\phi$in a complex field in the upper half-plane \[\tau = C_0 + i e^{-\phi} = C_0 +\frac{i}{g_s}~.\] $C_0$ has monodromy one around the D7-brane, meaning that going around the circle transforms it as $C_0 \to C_0 +1$.<br /><br />Now splitting the 10d metric as a 4d Minkowski space-time times a 6d manifold $B$ and requiring $\mathcal{N}=1$ susy in 4d implies that $B$ is a Kaehler manifold and that $\tau$ is (anti-)holomorphic: $\bar\partial \tau =0$.<br /><br />Mathematically, specifying the modular parameter $\tau$ in the fundamental region is equivalent to specifying an elliptic curve, and so this whole construction can be seen as an elliptic fibration $\pi: X\to B$, with $X$ a four complex dimensional manifold. The fibre over a point $p\in B$ on the base is an elliptic curve $E_{\tau}$ that is "biholomorphically" equivalent to a torus determined by a lattice $(1,\tau)$:<br />\[\pi^{-1} (p) \cong E_{\tau} \cong \mathbb{C}/(1,\tau)~.\]<br />What is very nice is that the D7-branes are located where the elliptic fibration degenerates, i.e. where the torus gets pinched off and becomes singular.<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgCVVMiuTQpOoaeX13CLLSgV5ilWoqmXMyzFVfrwQx-YYLcTgEFc-EEzMY6uPGi6EHpDPAzPoJy_HhESPJ7RFUM0tUt_M4RiQ-ynu9ItFGjwSSY9eadto-0zcx_BTGjoUKwz5F4Ey-N4vws/s1600-h/Slide1.jpg"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 320px; height: 240px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgCVVMiuTQpOoaeX13CLLSgV5ilWoqmXMyzFVfrwQx-YYLcTgEFc-EEzMY6uPGi6EHpDPAzPoJy_HhESPJ7RFUM0tUt_M4RiQ-ynu9ItFGjwSSY9eadto-0zcx_BTGjoUKwz5F4Ey-N4vws/s320/Slide1.jpg" alt="" id="BLOGGER_PHOTO_ID_5398419760747399970" border="0" /></a>James made the point that this is not just a mathematical construction since one can T-dualise to IIA and the lift to M-theory, where the resulting solution is the product of a 3d Minkowski space-time and a CY four-fold. Polchinski and Silverstein's idea is to get $AdS_5 \times \text{small}$ solutions by looking at CY four-fold cones that are elliptically fibered...Maximehttp://www.blogger.com/profile/17820669704568697363noreply@blogger.com0tag:blogger.com,1999:blog-4785174943828024073.post-55454725119204747922009-10-26T21:24:00.003+00:002009-10-27T11:16:28.540+00:00Etymology of yoToday, I think I made an etymological breakthrough: the interjection "yo", at least in some of its acceptations, is none other than the contraction of "you know". Word up!Maximehttp://www.blogger.com/profile/17820669704568697363noreply@blogger.com0tag:blogger.com,1999:blog-4785174943828024073.post-37054344900055418232009-10-23T15:33:00.009+01:002009-10-27T17:37:35.634+00:00"Gauge/gravity in three dimensions"Today's Theoretical Particle Physics seminar was given by Diego Rodriguez-Gomez (Queen Mary, U. of London), based mainly on <a href="http://arxiv.org/abs/0809.3237">0809.3237</a> and <a href="http://arxiv.org/abs/0903.3231">0903.3231</a>.<br /><br />Given the broad audience, he started by a small review of the AdS/CFT correspondence as a specially clean incarnation of 't Hooft's and Susskind's holographic principle. Whereas the 4d case has been relatively well understood for some time, the 3d case began to reveal itself only recently. In fact, until roughly two years ago, it was thought that the IR fixed point at the end of the RG flow of the maximally supersymmetric $\mathcal{N}=8$ SYM in 3d had no Lagrangian description. The reason for this belief was that the dual description has a non-constant dilaton blowing up at small radius: $e^{\phi} =(R/r)^{5/4}$. The BLG theory (anticipated by Schwarz) was an $\mathcal{N}=8$ Chern-Simons-like theory but it had an $SU(2)$ gauge group instead of the large $N$ needed in the AdS/CFT context. The resolution came from relaxing the requirement of maximal susy down to $\mathcal{N}=6$, which allowed arbitrary $N$ [ABJM].<br /><br />Diego was interested in reducing the supersymmetry to $\mathcal{N}=2$ by putting the M2-branes at the tip of a Calabi-Yau four-fold. He focused on a specific example: the cone over $Q^{1,1,1}$, which is similar to the conifold in 6d and has the advantage to have been extensively studied (the metric is explicitly known). The simplest proposal (inspired by crystal models) is that the dual field theory is a quiver with four gauge groups, six fields, and a sextic superpotential $W$ with two terms. As in the ABJM case, all the global symmetries are not manifest, but appear by studying how scalar fields get identified. This results in a mesonic moduli space that is an $\mathcal{N}=2$ orbifold $Q^{1,1,1}/\mathbb{Z}_2$. Here are the toric diagram and the associated quiver:<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjCP3gaQRdJ7WhccHIz0uCXTIriYq-bnv0iBb9aie21gM4hJ0-RyAon3IHfUIq7EGmpAWzW6hjOs3TETS37IQvBN-Ho4CruiDkLMRQcibciNv-H6JmIhT1Dzji0QIBnpSFFPINYbKFpAeaa/s1600-h/Q111.jpg"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 401px; height: 264px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjCP3gaQRdJ7WhccHIz0uCXTIriYq-bnv0iBb9aie21gM4hJ0-RyAon3IHfUIq7EGmpAWzW6hjOs3TETS37IQvBN-Ho4CruiDkLMRQcibciNv-H6JmIhT1Dzji0QIBnpSFFPINYbKFpAeaa/s320/Q111.jpg" alt="" id="BLOGGER_PHOTO_ID_5397334726926333618" border="0" /></a>Diego and his collaborators were able to show that the chiral operator spectrum is matching the supergravity harmonics, at least at large CS level $k$. This is a non-trivial check of the non-Abelian superpotential $W= C_1 A_1 B_1 C_2 A_2B_2 - C_1 A_1 B_2 C_2 A_2B_1$.<br /><br />Remaining mysteries include the question of whether theories with $\mathcal{N}<3$ susy are conformal, which would require to have an equivalent in 3d of a-maximization; the inverse algorithm (from the CY4 to the quiver) and the connection to type IIA string theory; the small $k$ limit and monopoles operators, which is the genuinely M-theoretic limit, since at large $k$ the theory reduces to IIA.Maximehttp://www.blogger.com/profile/17820669704568697363noreply@blogger.com0tag:blogger.com,1999:blog-4785174943828024073.post-29275700848288249772009-10-22T22:02:00.009+01:002009-10-27T00:40:46.171+00:00I. The necessity, structure, and priority of the question of BeingThis is a summary of the first section of the Introduction of Martin Heidegger's major work, <i>Being and Time</i> (1926), where he is aiming at reawakening an understanding of the meaning of the question of Being.<div><br /></div><div>I. THE NECESSITY, STRUCTURE, AND PRIORITY OF THE QUESTION OF BEING</div><div><br /></div><div>1. The Necessity for Explicitly Restating the Question of Being</div><div><br /></div><div>Since Plato and Aristotle the question of Being has been trivialized, and hence considered as superfluous. MH lists three prejudices, according to which this question is unnecessary. First, the assertion that 'Being' is the most universal concept does not imply that it is also the clearest: "It is rather the darkest of all." Secondly, even though 'Being' cannot be defined -- since a definition is typically of the form "something <i>is</i> this and that", it presupposes an understanding of the word "is" -- this does not eliminate the question of its meaning. Thirdly, the "self-evident" character of the concept of 'Being' remains, <i>a priori</i>, an enigma. So not only does the question of Being lack a clear answer, but "the question itself is obscure and without direction".</div><div><br /></div><div>2. The Formal Structure of the Question of Being</div><div><br /></div><div>The structure of any question splits into: that which is asked about [<i>sein Gefragtes</i>], the starting point of the curiosity; that which is interrogated [<i>sein Befragtes</i>], the things one turns to in order to find an answer; and that which is to be found out by asking [<i>das Erfragte</i>], the answer itself. </div><div><br /></div><div>In the case of the question of Being, the <i>Gefragtes</i> is... Being [damn! I knew it], or more explicitly "that which determines entities as entities". But "the Being of entities 'is' not itself an entity", in the sense explained above that Being cannot be defined. Rather, Being "must be exhibited in a way of its own" (quite intriguing ain't it?). [I'll hereinafter push the acronym perversity so far as to reduce Being to B.]</div><div><br /></div><div>The <i>Befragtes</i> are the entities themselves, that is "everything we talk about, everything we have in view, everything towards which we comport ourselves in any way" (a rather broad concept, mind you). [As an aside, I find such periphrases very revealing of the superiority of the German language to forge concepts.] But in sight of the unlimited possible choice, can one single out a specific entity that will be particularly useful to discern the meaning of B? Well we can, and it is ourselves, the inquirers. MH calls this special entity the "<i>Dasein</i>": "This entity which each of us is himself and which includes inquiring as one of the possibilities of its Being". What singles us out, among the infinities of entities, is the very fact that we are able to grow an interest in that which determines us as entities, i.e. our B.</div><div><br /></div><div>There is an apparent danger of 'circular reasoning': are we supposed to come to grip with the meaning of B by inquiring into entities that are inquiring into their own B by inquiring into entities that are inquiring into their own B by inquiring--you got it--? MH discards this "always sterile" argument, since (if I understand correctly) it is fine to 'presuppose' B "provisionally". No circular reasoning then, but "a remarkable 'relatedness backward and forward' " between the <i>Gefragtes</i> (B) and the <i>Befragtes</i> (us, <i>Dasein</i>). [This is somewhat reminiscent of self-consistent systems in condensed matter theory.]</div><div><br /></div><div>3. Ontological Priority of the Question of Being</div><div><br /></div><div>The message of this subsection is basically that "Basically, all ontology, no matter how rich and firmly compacted a system of categories it has at its disposal, remains blind and perverted from its ownmost aim, it if has not firstly clarified the meaning of B, and conceived this clarification as its fundamental task". What MH means (supposedly) is that among all the scientific investigations, the question of B is the most primordial. But I suspect that he doesn't mean "priority" in the sense that it has to come first. Indeed, in any of the fields of scientific research (or "areas of subject-matter"), the "basic concepts" are (provisionally, "beforehand") "worked out after a fashion in our pre-scientific ways of experiencing...". So the subject-matter of interest is primitively understood, may I say, intuitively, and it is over this original intuition that a science, that is a "system of categories", develops. But:</div><div><blockquote>"The 'real' movement of the sciences takes place when their basic concepts undergo a more or less radical revision which is transparent to itself. The level which a science has reached is determined by how far it is <i>capable</i> of a crisis in its basic concepts." (p.9)</blockquote></div><div>[Remark: I have a similar approach to evaluate the richness of a personality.] And MH to enumerate a few instances in science of what he perceives as "freshly awakened tendencies to put research on new foundations": the foundational crisis in <i>mathematics</i>, in spite of it being "seemingly the most rigorous and most firmly constructed of the sciences" (a clear presentiment of Goedel's incompleteness theorem of 1931); the "problem of matter" in the context of the relativity theory of <i>physics</i> (I don't understand his point at all, even at the seventeenth reading...); the "new kind of B" defined in <i>biology</i>; and the realisation of the "inadequate" foundation of <i>theology</i> (he's probably being polite).</div><div><br /></div><div>Ontological (concerned primarily with B) inquiries, such as Kant's <i>Critique of the Pure Reason</i>, are "more primordial" than the ontical (concerned primarily with entities) inquiry of the positive sciences. But they still lack an understanding of 'what we really mean by this expression "Being" '.</div><div><br /></div><div>4. The Ontical Priority of the Question of Being</div><div><br /></div><div>I find this last section more difficult to understand, perhaps because MH "anticipate[s] later analyses". Here we see listed and swiftly defined a series of key Heideggerian mottos and concepts. For instance, about Dasein, he is writing that "Being is an <i>issue</i> for it" and that</div><div><blockquote>"<i>Understanding of Being is itself a definite characteristic of Dasein's Bein</i>g. Dasein is ontically distinctive in that it <i>is</i> ontological."</blockquote></div><div>The distinction between "existentiell" and "existential" is also briefly described. As far as I can tell, the former means what you would naively expect, namely it characterises an understanding of existence, and more precisely Dasein's own existence.</div><div><blockquote>"Dasein always understands itself in terms of its existence--in terms of a possibility of itself: to be itself or not itself."</blockquote></div><div>(Here one can foresee the concept of authenticity.) MH underlines that Dasein is responsible for its existence, either actively or passively (for example, I suppose, if it lets external circumstances like childhood trauma dictate its conduct).</div><div><blockquote>"Only the particular Dasein decides its existence, whether it does so by taking hold or by neglecting."</blockquote></div><div>"Existential" on the other side characterises an understanding of the context of the "structure of existence".</div><div><blockquote>"By "existentiality" we understand the state of Being that is constitutive for those entities that exist."</blockquote></div><div>Coming back to the ideas of the previous section, MH writes that "Sciences are ways of Being in which Dasein comports itself towards entities which it needs not be itself", but his message is that Dasein "must first be interrogated ontologically." And just like the basic concepts of sciences are first worked out in a pre-scientific way, the question of B has to be worked out in a pre-ontological way:</div><div><blockquote>"the question of Being is nothing other that the radicalization of an essential tendency-of-Being which belongs to Dasein itself--the pre-ontological understanding of Being."</blockquote></div><div>This is the end of the first introduction of <i>Being and Time</i>.</div><div><br /></div><div>I mean come on! How amazing is that? The guy is slowly cracking the very kernel of the most fundamental question you can imagine, the question of Being. Heidegger was saying in an interview that an entirely new form of thought is now called for, in our modern time. It is simpler than the old way of thinking, more natural, but it is also more difficult, in that it requires a much greater care with the use of language. This perspective should be motivation enough to overcome the disgust inspired by the bestiary of Heideggerian concepts. So let's keep calm and carry on!</div>Maximehttp://www.blogger.com/profile/17820669704568697363noreply@blogger.com0tag:blogger.com,1999:blog-4785174943828024073.post-74764075592501532582009-10-16T15:27:00.018+01:002009-10-27T17:33:15.477+00:00"Topology and Relativity"OK, so for this Friday's Theoretical Physics Seminar we had Maulik Parikh from IUCAA in India talking about two of his current projects paired for the occasion under the title "Topology and Relativity".<br /><br /><span style="font-weight: bold;">Topology and special relativity</span><br /><br />This is a collaboration with Brian Greene and Jana Levin, to appear.<br /><br />The starting point is the twin paradox on a cylinder. For memory, the twin paradox in flat space-time concerns the age difference of two twins, one of which has been sent to the outer space and back. There is in fact no paradox, since the Principle of Relativity states that all <span style="font-style: italic;">inertial</span> observers are equivalent, whereas the space twin accelerated and decelerated on his Odyssey.<br /><br />In the case where space is a circle and time a line, and so on a space-time cylinder, both twins, gracefully christened A and B, could be inertial and still go their different ways and meet again. Who, then, asketh Maulik, is younger?<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhje8Zu2n11vOuWVEVGixN122ixSAV-f0a-fIjX2WyGYb0btpCsl_UH4jT1O5t2p1Y1J5uy8bpzpbkG8r5p1MsYP56Xtwq7jIut6Uj1-82zgmI4u1nbPr-y57Pgo8UoqUY6bY1DX8qvmUbL/s1600-h/cylinder.jpg"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 320px; height: 211px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhje8Zu2n11vOuWVEVGixN122ixSAV-f0a-fIjX2WyGYb0btpCsl_UH4jT1O5t2p1Y1J5uy8bpzpbkG8r5p1MsYP56Xtwq7jIut6Uj1-82zgmI4u1nbPr-y57Pgo8UoqUY6bY1DX8qvmUbL/s320/cylinder.jpg" alt="" id="BLOGGER_PHOTO_ID_5397334073863311954" border="0" /></a>Well, the catch is that the periodic identification of the space coordinate picks a globally preferred frame (the one with winding number zero I suppose). So the first lesson is that<br /><br /><span style="font-style: italic;">A nontrivial topology breaks global Lorentz symmetry.</span><br /><br />The preferred frame could be determined by experiments by sending photons in different directions. In particular, Einstein clock synchronization would only be possible for preferred observers. There is also a discontinuity in the time coordinate, as the inhabitants of Kiribati, lying (not anymore since 1995) on the International Date Line, know very well (after all, as far as time zones are concerned, the Earth's worldvolume is essentially a cylinder).<br /><br />Suppose there is a compact extra dimension (of mm size according to the ADD scenario). Can we tell the velocity of our (3+1)-brane around it? Obama says "Yes we can!", for which Maulik thinks he should get the Physics Nobel Prize as well...<br /><br />If the LHC fires gravitons in the extra dimensions, then measuring their return time could make it possible to determine the motion of the brane. This is in fact not realistic, since graviton interactions are suppressed by the Planck mass.<br /><br />Another effect of an compact extra dimension would be a modification of Newton's law. Since a source placed at a point along the extra coordinate would be repeated infinitely at interval $L$, the standard potential<br />\[<br />V(r) = -\frac{GM}{\pi r^2}<br />\]would be replaced by<br />\[<br />V(r) = -\frac{GM}{\pi } \sum_{n=-\infty}^{\infty} \frac{1}{r^2 +(nL)^2}\\<br />\simeq -\frac{GM}{r} (1+ 2e^{-2\pi r/L})~.<br />\]For a moving brane, one would have to replace $L$ by $\gamma L$ where $\gamma$ is the relativistic factor. This opens the amusing possiblity of a <span style="font-style: italic;">magnified extra dimension</span>, if our brane were to move ultra-relativistically.<br /><br /><span style="font-weight: bold;">Topology and the Fate of the Universe</span><br /><br />The second part of Maulik's talk was on a disconnected topic, base on his paper <a href="http://arxiv.org/abs/0909.3307">Enhanced Instability of de Sitter Space in Einstein-Gauss-Bonnet Gravity</a>. The geometry of the early universe is well-described by de Sitter space, which is perturbatively stable. However, Bousso and Hawking showed that dS space can be destabilized by non-perturbative effects (such as instantons, black hole tunneling, etc.). The probability of a gravitational instanton is<br />\[<br />\Gamma \sim \frac{\exp(-I_E[\text{instanton}])}{\exp(-I_E[\text{background}])}~.<br />\]where $I_E$ is the Euclidean action. Now instead of taking the usual Hilbert-Einstein action, Maulik considered the Einstein-Gauss Bonnet action (which appears for instance in the low energy effective action of heterotic string theory). The novelty is the in our dimension the Gauss-Bonnet action is a topological invariant<br />\[<br />I_{GB} = -\frac{\Lambda V_4}{8\pi G} - \frac{2\pi \alpha}{G} \chi~,<br />\]where $\Lambda$ is the cosmological constant, $V_4$ is the volume, $\alpha$ the coupling constant, and last but not least $\chi$ is the <a href="http://www.claymath.org/public_lectures/">Euler</a> number.<br /><br /><span style="font-style: italic;">The Gauss-Bonnet topological term can enhance the instability of primordial de Sitter space.</span><br /><br />In the case of the extremal Nariai black hole with topology $S^2\times S^2$, using the Hilbert-Einstein action as Bousso and Hawking did leads to an instanton probability $\Gamma = \exp[(-\pi L^2/3G)$, which means this is only relevant for a length scale $L$ close to the Planck scale. Disappointing.<br /><br />In contrast, with its additional topological term, the EGB action leads to an enhanced production of Nariai black holes (with $\chi =2+2=4$) by a factor of $\exp(4\pi\alpha/G)$.<br /><br />Maulik also mentioned a bound on the maximal curvature of empty dS space.<br /><br />Other applications include the effect of the topological term on the probabilities of Calabi-Yau manifolds in the string landscape. For example, the quintic has $\chi=-200$, which means it could be suppressed by roughly $\exp(-2000)$.Maximehttp://www.blogger.com/profile/17820669704568697363noreply@blogger.com0tag:blogger.com,1999:blog-4785174943828024073.post-28765980945857532732009-10-12T16:02:00.032+01:002009-11-29T22:29:13.119+00:00"Mirror symmetry, Langlands duality, and the Hitchin system"Today, at the Geometry and Analysis Seminar organized by Nigel Hitchin, Tamas Hausel talked about his paper with Michael Thaddeus <a href="http://arxiv.org/abs/math/0205236">Mirror symmetry, Langlands duality, and the Hitchin system</a>. The room was packed. He started by giving some background informations about the three concepts in his title.<br /><br /><span style="font-weight: bold;">Mirror symmetry</span><br /><br />The basic idea is that the symplectic geometry of a <span style="font-style: italic;">d</span>-dimensional Calabi-Yau manifold $X$ can be related to the complex geometry of another CY manifold $Y$. There is a topological test of this relation, referred to as topological mirror symmetry, which equates (mirror pairs of) Hodge numbers of the two CYs:<br />\[ h^{p,q} (X) = h^{d-p,q}(Y)~. \]<div>Note that any hyperkaehler manifold satisfies $h^{p,q} (X) = h^{d-p,q}(X)$, so in a certain sense TMS is already built-in. Tamas mentioned two important developments in the history of mirror symmetry: homological mirror symmetry proposed by Kontsevich in 1994, which reads<br />\[<br />\mathcal{D}^b (\text{Fuk}(X,\omega)) \cong \mathcal{D}^b (\text{Coh}(Y,I))~,<br />\] where $\omega$ is the symplectic form and $I$ the complex structure. Another breakthrough was the geometric construction of $Y$ from $X$ elaborated by Strominger, Yau and Zaslow in 1996.<br /><br /><span style="font-weight: bold;">Langlands duality</span><br /><br />The aim of the Langlands program is to describe $\text{Gal}(\bar{\mathbb{Q}}/\mathbb{Q})$ via representation theory.<br />To each reductive group $G$ is associated a Langlands dual $^LG$. The Langlands conjecture leads for instance to class field theory, in the case $G=GL_1$; in the case $G=GL_2$, it leads to the Taniyama-Shimura conjecture (which is famous because it implies Fermat's last theorem). An important progress towards the proof of the conjecture was made by Ngo in 2008 with his proof of the fundamental lemma for the function field $\mathbb{F}_q(X)$.<br />There is a geometric version of the conjecture, obtained by replacing $\mathbb{F}_q(X)$ by $\mathbb{C}(X)$ for $X/\mathbb{C}$ (Laumon 1987, Beilinson & Drinfeld 1995):<br />\[<br />\{ G\text{-local systems on $X$} \}<br />\]\[<br />\leftrightarrow \{ \text{Hecke eigensheaves on Bun$_{^LG}(X)$}\}~.\]<br /><span style="font-weight: bold;">Hitchin systems</span><br /><br />Recall that a Hamiltonian system $(X^{2d}, \omega)$ has an energy functional $H: X\to \mathbb{R}$ and an Hamiltonian vector field $X_H$ such that $\text{d}H=\omega(X_H,\cdot)$. A function $f:X\to \mathbb{R}$ is a first integral if $X_H f = \omega(X_H, X_f) =0$ (involution). The system is completely integrable if there is $d$ first integrals. The generic fibre is then a torus (examples: Euler and Kovalevskaya tops, spherical pendulum).<br />An algebraic version is obtaiend by replacinf $\mathbb{R}$ by $\mathbb{C}$, and many examples can be formulated as Hitchin systems (1987).<br /><br />Now I cannot say I completely followed the rest of the talk in all its glory, but I'll try to restate what I understood. Tamas was considering different moduli spaces, which are all smooth non-compact varieties: $\mathcal{M}_{\text{Dol}}^d (G)$ is the moduli space of rank $n$ and degree $d$ Higgs bundles $(E,\phi)$, $\mathcal{M}_{\text{DR}}^d (G)$ is the moduli space of flat $G$-connections on a genus $g$ curve, $\mathcal{M}_{\text{B}}^d (G)$ is yet another thing -- but they're all equivalent by a non-Abelian Hodge theorem. The Hitchin map $\chi(\phi)$ is completely integrable and its fibre $\chi^{-1}(a)$ is a torsor.<br /><br />Inspired by the SYZ conjecture, Hausel and Thaddeus noticed in 2003 that $\chi^{-1}_{SL_n}(a)$ and $\chi^{-1}_{PGL_n}(a)$ are torsors for dual Abelian varieties. (I think this means they are related by T-duality on the toroidal Hitchin fibres, but he said "fibrewise Fourier-Mukai tranform" instead :)<br /><br />A confirmation that their conjecture are more or less sane came from the 2006 work of <a href="http://arxiv.org/abs/hep-th/0604151">Kapustin and Witten</a> on S-duality (electric-magnetic duality) in $\mathcal{N}=4$ super-Yang-Mills in four dimensions, which Tamas qualified as "a major work" with many fertile ideas. (In fact T-duality in the Hitchin moduli space corresponds to S-duality in the gauge theory, see Witten's <a href="http://insti.physics.sunysb.edu/itp/conf/simonswork3/">Strings on the Beach!</a> talk in 2005.)<br /><br />Using stringy Hodge numbers (also known as "orbifold cohomology") Tamas made a conjecture with a TMS test, but he also made another one using mixed Hodge numbers.<br />His final questions were: "Why two conjectures? Why same Hodge numbers instead of mirrored ones? Why Geometric Langlands and not classical Langlands?<br /><br />He ended up by mentioning a curious hard Lefschetz conjecture for weight and perverse filtrations that left the crowd speechless.</div>Maximehttp://www.blogger.com/profile/17820669704568697363noreply@blogger.com0tag:blogger.com,1999:blog-4785174943828024073.post-53874730058985445322009-10-08T17:20:00.028+01:002009-10-18T14:47:12.456+01:00"Adding Flavor to AdS4/CFT3"I thought I would try to write short summaries of interesting talks I attend here in Oxford. The first one of Hilary term is<br /><br /><span style="font-style: italic;">Adding Flavor to AdS4/CFT3 </span>by Andy O'Bannon from the Max Planck Institut in Munich, based on <a href="http://arxiv.org/abs/0909.3845">0909.3845</a>.<br /><br />The motivation is that the AdS/CFT correspondence only really becomes useful for applications (quark-gluon plasma at RHIC, condensed matter systems, often 3-dimensional) when it involves not only fields in the adjoint representation of the gauge group---strings starting and ending on the same brane---but also fields in the fundamental representation. For this one needs to add new branes so that strings can stretch between different branes.<br /><br />Such procedure is well-understood in the AdS5/CFT4 context: the supergravity action acquires a new term describing the new Dp-branes (be it D5 or D7), $\large S_{10d} = S_{IIB} + S_{Dp}$, and this is dual to super-Yang-Mills with flavors in 4d, $S_{4d} = S_{\mathcal{N}=4} + S_{\text{flavor}}$. The story in M-theory is less understood. The "membrane minirevolution" (as Lubos calls it) led to a duality between $N_c$ M2-branes with a $AdS_4 \times S^7/\mathbb{Z}_k$ horizon, and a (2+1)dimensional Chern-Simons theory with N=6 supersymmetries with fields in the bifundamental of $U(N_c)_k \times U(N_c)_{-k}$. This is the famous ABJM theory (see <a href="http://arxiv.org/abs/0909.1580">Klebanov & Torri </a>for a recent review). The goal of the talk is to understand what happens on the field theory side when on add M5-branes. What is the $S_{\text{flavor}}$ dual to $S_{M5}$?<br /><br />Since the whole heuristic argument is based on being able to use the intuition of a string stretched between different branes being in the fundamental, and since there is no string in M-theory, the strategy is to start with type IIB supergravity with $N_c$ D3-branes, add Dp-branes and NS5-branes to get some flavor, and then T-dualise to IIA and lift to eleven-dimensional supergravity, the low-energy limit of M-theory. Here is roughly how it goes.<br /><br />The D3-branes are first considered as hanging along one direction between two NS5-branes, as so (thanks to Cyril for allowing me to use his drawing device:):<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiDIxbTS2cNEPPOY-YBmq951vp98UA4AOWV1vUanl4lzVt74WJZ-F10_xSCgQQJOaSsf4566pOjCF90La6GgIm4gfAL0Dricu0yRGAdAH6gydXa8hobTw-PhuAusq6YEZ3I4oM4PEPytAVE/s1600-h/NS5D3NS5.jpg"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 320px; height: 214px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiDIxbTS2cNEPPOY-YBmq951vp98UA4AOWV1vUanl4lzVt74WJZ-F10_xSCgQQJOaSsf4566pOjCF90La6GgIm4gfAL0Dricu0yRGAdAH6gydXa8hobTw-PhuAusq6YEZ3I4oM4PEPytAVE/s320/NS5D3NS5.jpg" alt="" id="BLOGGER_PHOTO_ID_5390274769830888834" border="0" /></a>Now perform a dimensional reduction on this compact interval and you get a (2+1)d SYM with N=4 and gauge group $U(N_c)$. If you replace one NS5 by a (1,k)5 = NS5 + k D5, then you get (after considering bounday terms...) a Chern-Simons theory with level k. Pretty close already!<br /><br />Now consider two stacks of D3-branes stretched between the (1,k)5 and the NS5<br />(the (1,k)5 has to be tilted to preserve N=3 superymmetries, with and angle $\large \tan\theta = k$):<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgaqvdRmqiwvPBR_G_yUNKVC_F1TXCnza_ilh8Mf7fv-RZ8Vwm8kcTKsgREobWTQvpYsI5mMzKNr8tWhrap41f7guzib-6LagkbHqrBvdrNVX41kom1Ag2b1ezETQBf4Jus8mYNCw8rxDfg/s1600-h/1k5D3NS5.jpg"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 320px; height: 214px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgaqvdRmqiwvPBR_G_yUNKVC_F1TXCnza_ilh8Mf7fv-RZ8Vwm8kcTKsgREobWTQvpYsI5mMzKNr8tWhrap41f7guzib-6LagkbHqrBvdrNVX41kom1Ag2b1ezETQBf4Jus8mYNCw8rxDfg/s320/1k5D3NS5.jpg" alt="" id="BLOGGER_PHOTO_ID_5390278167882336018" border="0" /></a>What you get now is a CS theory with N=3 and fields in the bifundamental of $U(N_c)_k \times U(N_c)_{-k}$, which is starting to realy look like the ABJM theory. The superymmetry can be enhanced because of Kaluza-Klein monopoles (which correspond on the field theory side to take the low energy limit by integrating out masses greater than $g_{YM}^2 k$) but Andy passed over this important subtlety, and so do I.<br /><br />All that is left to do is to T-dualise this whole brane construction and lift to eleven dimensions to produce M2-branes and Kaluza-Klein monopoles (which are described purely geometrically...):<br />\[D3 \to D2 \to M2 \]<div>\[NS5 \to KK \to KK \]</div><div>\[(1,k)5 \to KK + D6 \to KK'\]</div><div>The KK monopoles interesect at a $\mathbb{C}^4/\mathbb{Z}_k$ orbifold singularity, and placing $N_c \to \infty$ M2-branes at this singularity produces a near-horizon geometry $AdS_4 \times S^7/\mathbb{Z}_k$, which is dual to the ABJM theory.<br /><br />So now to understand flavors in AdS4/CFT3 you can add some Dp-branes in the IIB background and repeat this translation procedure to M-theory. Andy went through two examples, one with D5-branes, the other with D-branes, and showed that they in fact both lead to the same CS theory with flavor and $SU(4) \times U(1)$ isometry.<br /><br />He finished by mentioning an application: fractional quantum Hall effect.</div>Maximehttp://www.blogger.com/profile/17820669704568697363noreply@blogger.com0tag:blogger.com,1999:blog-4785174943828024073.post-72894354614463511132009-10-04T17:12:00.020+01:002009-12-04T23:35:06.888+00:00Merleau-Ponty: L'Œil et l'Esprit<i>L'Œil et l'Esprit</i>, écrit en 1960, est le dernier texte de Maurice Merleau-Ponty (1908-1961). J'en ai souligné quelques passages et je tente maintenant d'en restituer l'argument. [Désolé pour l'état squelettique de cette note..]<div><br /></div><div style="text-align: center;"><b>Section I</b></div><div><span class="Apple-style-span" style="font-family:'times new roman', serif;"><br /></span></div><div>MMP (c'était aussi le surnom d'un charismatique professeur à la barbe blanche de <i>Quantentheorie</i> à la <i>Humboldt Universität</i>:) prend le problème du désenchantement de la science moderne comme point de départ.</div><div><br /></div><div>"La science manipules les choses et renonce à les habiter." (p.9, première phrase du folio)</div><div><br /></div><div>"Il faut que la pensée de science -- pensée de survol, pensée de l'objet en général -- se replace dans un « il y a » préalable, dans le site, sur le sol du monde sensible et du monde ouvré tels qu'ils sont dans notre vie, pour notre corps, non pas ce corps possible"…</div><div>"Dans cette historicité primordiale, la pensée allègre et improvisatrice de la science apprendra à s'appesantir sur les chose mêmes et sur soi-même, redeviendra philosophie…" (p.12-13)</div><div><br /></div><div>La solution doit venir de la peinture, le vrai sujet qui intéresse MMP.</div><div><br /></div><div>"Or l'art et notamment la peinture puisent à cette nappe de sens brut dont l'activisme ne veut rien savoir." (p.13)</div><div><br /></div><div>Note comme la ponctuation, son absence en fait, indique bien comme MMP ne compte pas s'appesantir sur les autres arts que la peinture, qu'il discrédite tous en deux phrases expédiées. Lui, c'est la peinture son truc.</div><div><br /></div><div>"Le peintre est seul à avoir droit de regard sur toutes choses sans aucun devoir d'appréciation." … "Quelle est donc cette science secrète qu'il a ou qu'il cherche?"</div><div><br /></div><div>Le décor est planté.</div><div><br /></div><div style="text-align: center;"><b>Section II</b></div><div><br /></div><div>MMP essaie de cerner "cet extraordinaire empiétement" du monde tel que nous le voyons et du monde dans lequel nous nous déplaçons (je ne suis pas certain de bien le suivre ici; oppose-t-il la perception visuelle à la perception tactile?).</div><div><br /></div><div>"C'est en prêtant son corps au monde que le peintre change le monde en peinture." …</div><div>"Le monde visible et celui de mes projets moteurs sont des parties totales du même Être." (p.16-17)</div><div><br /></div><div>"L'énigme tient en ceci que mon corps est à la fois voyant et visible." (p.18)</div><div><br /></div><div>"… l'indivision de sentant et du senti." (p.20)</div><div><br /></div><div>C'est intéressant, et j'aimerais y acquiescer (et faire le lien avec la théorie quantique, éventuellement…), mais je peine à trouver la substance de sa réflexion. Ses formules sonnent creux:</div><div><br /></div><div>"le dessin et le tableau"… "sont le dedans du dehors et le dehors du dedans"… (p.23)</div><div><br /></div><div><i>See what I mean?</i></div><div><br /></div><div>Ce qui a le plus excité mon crayon sont des citations:</div><div><br /></div><div>"« <b>la nature est à l'intérieur </b>», dit Cézanne." (p.22)</div><div><br /></div><div>"Max Ernst"… "« … le rôle du peintre et de cerner et de projeter ce qui se voit en lui. »" (p.30)</div><div><br /></div><div>Même si je ne suis pas emballé par l'argumentation de MMP, je trouve ces citations très inspirantes. Après tout, ce n'est pas réellement les sortir de leur contexte, MMP s'en est déjà chargé.</div><div><br /></div><div>(Il m'arrive d'ailleurs souvent d'aimer une citation au fi de son utilisation particulière. Par exemple, bien que je ne me soie pas à vrai dire délecté de <i>La Porte Etroite</i> (1909) d'André Gide (1869-1951), j'ai été profondément touché par une citation paradoxale du Christ, elle-même tirée de Pascal: "Qui veut sauver sa vie la perdra.")</div><div><br /></div><div>Ce que j'aime dans la citation de Cézanne, c'est sa force et sa beauté brute. Elle est faite de mots simples, tirés du langage quotidien, et pourtant elle frappe l'entendement et fait résonner les hautes sphères spirituelles. La nature, c'est ce qu'il y a devant moi, là, ce que je vois par-delà ma fenêtre. Et en moi sont mes sentiments et mes idées, immatérielles et intimes. Et bien les deux ne s'opposent pas, on ne peut pas poser l'une comme fondamentale (tels les cartésiens l'esprit, ou les positivistes la réalité physique) et y prendre appui pour explorer l'autre, non. Les deux sont une seule et même chose, et il ne fait sens de les considérer qu'en conjonction.</div><div><br /></div><div>"Les parfums, les couleurs et les sons se répondent." Certes, certes, bravo Charles, voilà qui devrait faire mollir les âmes tendres, mais ce n'est pas tout! La nature est à l'intérieur. Comprends bien ça.</div><div><br /></div><div>Quand Cézanne peint la montagne Sainte-Victoire (plagié-je?), il se fout pas mal du paysage, tout comme il se fout pas mal du panier de pommes qu'il peint. Ce qui l'intéresse c'est l'intérieur, ou plutôt le fait hallucinant que la montagne, toute géologique qu'elle puisse être, elle est à l'intérieur. A l'intérieur de lui, quand il la voit.</div><div><br /></div><div>Et c'est là que MMP nous dit à point</div><div><br /></div><div>"la peinture ne célèbre jamais d'autre énigme que celle de la visibilité." (p.26)</div><div><br /></div><div style="text-align: center;"><b>Section III</b></div><div><br /></div><div>"Comme tout serait plus limpide dans notre philosophie si l'on pouvait exorcise ces spectres, en faire des illusions ou des perception sans objet, en marge d'un monde sans équivoque! La <i>Dioptrique</i> de Descartes est cette tentative. C'est le bréviaire d'une pensée qui ne veut plus <b>hanter</b> le visible et décide de la reconstruire selon le modèle qu'elle s'en donne." (p.36)</div><div><br /></div><div>On croirait presque entendre le sarcasme des physiciens quantiques à l'égard de ceux qui (comme Einstein) ne veulent pas abandonner leur rêves déterministes... </div><div><br /></div><div>Le mot clé ici est "hanter". Si nous étions immortels nous pourrions nous en passer. A défaut, nous hantons, et c'est tant mieux.</div><div><br /></div><div>Après avoir discrédité "la chose même" et "l'espace en soi", "l'en soi par excellence" cartésiens, MMP concède</div><div><br /></div><div>"Descartes avait raison de délivrer l'espace. Son tort était de l'ériger en un être tout positif, au-delà de tout point de vue, de toute latence, de toute profondeur, sans aucune épaisseur vraie." (p.48)</div><div><br /></div><div>J'aime bien cette idée qu'il est nécessaire de passer par une étape de pensée rigide, positiviste, réaliste, avant de pouvoir dans un deuxième temps s'en affranchir et accepter l'incertitude. MMP nous dit par exemple que </div><div><br /></div><div>"<b>l'espace n'a pas trois dimensions</b>"</div><div><br /></div><div>en quoi, de nouveau, je serais friand de pouvoir le suivre mais je ne vois pas bien comment.</div><div><br /></div><div>"les dimensions sont prélevées par les diverses métriques sur une dimensionnalité, un Être polymorphe, qui les justifie toutes sans être complètement exprimé par aucune."</div><div><br /></div><div>Mais, ai-je presque envie de dire, cet "Être polymorphe" est-il Calabi-Yau?</div><div><br /></div><div>Si je comprends bien, la dimensionnalité serait une propriété du mode de perception plus qu'une propriété intrinsèque des choses. Une qualité secondaire, et non une qualité primaire. Hm. Intéressant.</div><div><br /></div><div>"Quelque chose dans l'espace échappe à nos tentatives de survol." (p.50)</div><div><br /></div><div>"En vérité il est absurde de soumettre à l'entendement pur le mélange de l'entendement et du corps." (p.55)</div><div><br /></div><div>La science moderne, nous dit MMP, est tellement dégénérée, plus cartésienne que Descartes etc, qu'il nous en faudrait une autre, entièrement nouvelle, pour pouvoir envisager une cohabitation amicale avec la philosophie.</div><div><br /></div><div>"si nous retrouvons un équilibre entre la science et la philosophie, entre nos modèles et l'obscurité du « il y a », il faudra que ce soit un nouvel équilibre. Notre science a rejeté aussi bien les justifications que les restrictions de champ que lui imposait Descartes."</div><div><br /></div><div>"La pensée opérationnelle"... "est fondamentalement hostile à la philosophie comme pensée au contact"... (p.57)</div><div><br /></div><div>"Notre science et notre philosophie sont deux suites fidèles et infidèles du cartésianisme, deux monstres nés de son démembrement."</div><div><br /></div><div>Et voici la voie à suivre selon MMP:</div><div><br /></div><div>"Nous <i>sommes</i> le composé d'âme et de corps"... (p.58)</div><div><br /></div><div>"L'espace n'est pas celui dont parle la <i>Dioptrique</i>, réseau de relations entre objets, tel que le verrait un tiers témoin de ma vision, ou un géomètre qui la reconstruit et la survole, c'est un espace compté à partir de moi comme point ou degré zéro de la spatialité. Je ne le vois pas selon son enveloppe extérieure, je le vis du dedans, j'y suis englobé."... "La lumière est retrouvée comme action à distance, et non plus réduite à l'action de contact"... (p.58-59)</div><div><br /></div><div>"Toutes les recherches que l'on croyait closes se rouvrent. Qu'est-ce que la profondeur, qu'est-ce que la lumière"... " non pas pour l'esprit qui se retranche du corps, mais pour celui dont Descartes a dit qu'il y était répandu"...</div><div><br /></div><div style="text-align: center;"><b>Section IV</b></div><div style="text-align: center;"><br /></div><div>MMP nous dit qu'il a le sentiment </div><div><br /></div><div>"d'une discordance profonde, d'une mutation dans les rapports de l'homme et de l'Être, quand il confronte massivement un univers de pensée classique avec les recherches de la peinture moderne." (p.63)</div><div><br /></div><div>"Quatre siècles après les « <a href="http://www.youtube.com/watch?v=Mi6gr1jTerg">solutions</a> » de la Renaissance et trois siècles après Descartes, la profondeur est toujours neuve"... (p.64)</div><div><br /></div><div>"De la profondeur ainsi comprise, on ne peut plus dire qu'elle est « troisièmes dimension »." (p.65)</div><div><br /></div><div>Et de nouveau une très belle contribution de Cézanne au débat:</div><div><br /></div><div>"Quand Cézanne cherche la profondeur, c'est cette déflagration de l'Être qu'il cherche, et elle est dans tous les modes de l'espace, dans la forme aussi bien. Cézanne sait déjà ce que le cubisme redira : que la forme externe, l'enveloppe, est seconde, dérivée, qu'elle n'est pas ce qui fait qu'une chose prend forme, qu'il faut la briser cette couille d'espace, rompre le compotier --- et peindre, à la place, quoi?"</div><div>[Le lecteur attentif aura remarqué une coquille dans le mot "coquille" -- justement...]</div><div><br /></div><div>"C'est donc ensemble qu'il faut chercher l'espace et le contenu."</div><div><br /></div><div>La couleur est "« l'endroit où notre cerveau et l'univers se rejoignent »"</div><div><br /></div><div>(comme la théorie des cordes;)</div><div><br /></div><div>"C'est cette animation interne, ce rayonnement du visible que le peintre cherche sous les noms de profondeur, d'espace, de couleur."</div><div><br /></div><div>"L'effort de la peinture moderne n'a pas tant consisté à choisir entre la ligne et la couleur, ou même entre la figuration des choses et la création de signes, qu'à multiplier les systèmes d'équivalences,"...</div><div><br /></div><div>Ce qui me fait penser aux dualités de la physique théorique...</div><div><br /></div><div>Il y a aussi un passage sur le cinéma et la photo.</div><div><br /></div><div>"Rodin a ici un mot profond : « C'est l'artiste qui est véridique et c'est la photo qui est menteuse, car, en réalité, le temps ne s'arrête pas. »" (p.80)</div><div><br /></div><div>"La peinture ne cherche pas le dehors du mouvement, mais ses chiffres secrets."</div><div><br /></div><div>La vision est "le moyen qui m'est donné d'être absent de moi-même, d'assister de dedans à la fission de l'Être, au terme de laquelle seulement je me ferme sur moi."</div><div><br /></div><div>..."par elle nous touchons le soleil, les étoiles, nous sommes en même temps partout"...</div><div><br /></div><div>"la «simultanéité » ''' mystère que les psychologues manient comme un enfant des explosifs." </div><div><br /></div><div>Parle-t-il de la synchronicité de Jung?</div><div><br /></div><div>... "le propre du visible est d'avoir une doublure d'invisible"...</div><div><br /></div><div style="text-align: center;"><b>Section V</b></div><div><br /></div><div>... "profondeur, couleur, forme, ligne, mouvement, contour, physionomie sont des rameaux de l'Être"...</div><div><br /></div><div>A propos du "vrai peintre":</div><div><br /></div><div>"Même quand elle a l'air partielle, sa recherche est toujours totale."</div><div><br /></div><div>A rapprocher de la façon dont Tim Gowers explique dans sa conférence <i><a href="http://www.claymath.org/annual_meeting/2000_Millennium_Event/Video/">The Importance of Mathematics</a></i> au <i>Clay Mathematics Institut</i>e en 2000 qu'il serait faux de discréditer les domaines de recherches mathématiques qui paraissent les moins applicables parce que les mathématiques forment un réseau intriqués de connexions, et qu'on ne peut en couper une partie sans par la même occasion en affaiblir la totalité organique..</div><div><br /></div><div>... "la trouvaille est ce qui appelle d'autre recherches. L'idée d'une peinture universelle, d'une totalisation de la peinture, d'une peinture toute réalisée est dépourvue de sens." (p.90)</div><div><br /></div><div>(tout comme l'idée d'une <i>Theory of Everything</i>...)</div><div><br /></div><div>"Le plus haut point de la raison est-il de constater ce glissement du sol sous nos pas, de nommer pompeusement interrogation un état de stupeur continuée, recherche un cheminement en cercle, Être ce qui n'est jamais tout à fait?</div><div>Mais cette déception est celle du faux imaginaire, qui réclame une positivité qui comble exactement son vide. C'est le regret de n'être pas tout."</div><div><br /></div><div>... "chaque création change, altère, éclaire, approfondit, confirme, exalte, recrée ou crée d'avance toutes les autres."</div><div><br /></div><div><br /></div>Maximehttp://www.blogger.com/profile/17820669704568697363noreply@blogger.com2tag:blogger.com,1999:blog-4785174943828024073.post-50743287387351463892009-07-19T23:41:00.008+01:002009-07-28T10:28:32.965+01:00Zen Zoe<div style="text-align: left;">If you wander around in one of Oxford's many parks, you might meet an old lady peacefully drawing on a huge sheet of paper. Well, it's Zoe Peterssen. The rest of the story has been told many times, for instance <a href="http://www.insideadog.com.au/residence/index.php/liliwilkinson/trees-of-oxford/">here</a>---needless to say that I was quite disappointed to see that many people had experienced just the same intimacy with Zoe, and that I wasn't "special" at all, she opened up to pretty much everybody. Fuck you for that Zoe bitch!</div><div><br /></div><div>Under such circumstances, I'll just restrain to a couple of remarks.</div><div><br /></div><div>Firstly, about her technique. She's drawing on huge sheets of paper, I told that already. What's surprising then, is that the next step is to photocopy those sheets repeatedly, reducing the size by half every time, until the tree is small enough to hold on a little card that she gracefully gives to wanderers that she likes (who are welcomed to then also give her something, a few pounds will do). So from say 2 meters to 3 centimetres, she must photocopy a drawing six times. What a labour! This shrinking process is actually akin to bonsai growing.</div><div><br /></div><div>This comparison came to me because when I said that I was doing particle physics she mentioned a book she'd read about it, <i>The Tao of Physics</i> by Fritjof Capa (1975). I'd like to re-read this book.</div><div>She also mentioned bows and told the story of a man who wanted to learn archery and spent many years at it until finally he shot an arrow without feeling any shot, to which his Zen master said that he now knew how to shoot an arrow. I'd like to know how to shot an arrow.</div><div><div><br /></div><div><span class="Apple-style-span" style="color: rgb(0, 0, 238); -webkit-text-decorations-in-effect: underline; "><img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiky5oSZcLwkvFNajTNspX4xCQJVT-nTcL0OPVgLXrb8d0fHJWTDuFXQlRwqfoKSLyW4q3yhUsuAOouE0_KRQK9EeRFI16T-sTqDEOJtvtsRJKohpI9binaR2vz32D88E5pFAJyk2BnE0DD/s320/ZoeTrees.JPG" border="0" alt="" id="BLOGGER_PHOTO_ID_5361047961058194914" style="display: block; margin-top: 0px; margin-right: auto; margin-bottom: 10px; margin-left: auto; text-align: center; cursor: pointer; width: 240px; height: 320px; " /></span></div></div>Maximehttp://www.blogger.com/profile/17820669704568697363noreply@blogger.com3tag:blogger.com,1999:blog-4785174943828024073.post-5771863927859907382009-06-24T21:28:00.013+01:002009-07-28T10:29:01.241+01:00Masterclass with Mitsuko UchidaYesterday I went to a master class given by Mitsuko Uchida to four performance students of the Music Faculty. The students presented pieces by Schubert, Schumann, Bach, and Beethoven. It was fascinating to see how much emotion and contrast she was able to percieve in those pieces and how well she could communicate it. She used a variety of ways to do it: obviously by playing herself on the piano, and by singing and screaming, but also with her body, directing with her hands and dancing, jumping around really, but also through more indirect ways. She used metaphors, she talked about a "dry sunny day, when it hasn't rained yet and you can smell the warm sand" and so on. She also resorted to musical analysis, for instance she explained how Bach was moving between the tonic, the dominant, and the sub-dominant---in fact, she apologized for having to sound so technical but it was just a way for her to express how she felt the piece should be played, what was at stake, what psychological tensions and what resolutions.<div><br /></div><div>The precious moments when Mitsuko was playing for more than two seconds revealed the depth of her concentration and total involvement into the music. It was amazing---also certainly completely unavoidable to any great performer---how she was never playing lightly, but always mobilizing her full life's experience, all her pains, all her joys, all her emotions and sensations, her entire mind and body focused on the musicality. </div><div><br /></div><div>She had something of a yoga teacher trying to encourage her students to stretch their bodies. She has probed the extremities of the various human emotions. One advice that struck me particularly and that she repeated to almost every performer of the day (at least the girls) was not to play "too beautifully". She encouraged them not to iron the peculiarities, the oddities of the compositions, but on the contrary to make the strangeness emerge, accentuate the dissonance, show how bizarre reality is. (It is something I think about a lot these days, bringing out the surreal...) </div><div>So you had for example this nice little American blonde playing as beautifully as she could, and hirsute Mitsuko shouting to her to play it uglier. At some point she told her "Play with your biggest pain!"</div><div><br /></div><div>She also got mad when one of the students told her that the reason she was playing in a certain way was because of the influence of some famous pianist (although I think she misunderstood what the student meant). She said that every interpret makes mistake and so it is pointless to copy them, one should create her/his own mistakes :)</div><div><br /></div><div>Mitsuko has recently become a 'Dame' and </div><div>today she was receiving and <a href="http://www.ox.ac.uk/media/news_stories/2009/090619.html">honorary doctorate</a> at Oxford's <i>Encaenia</i> Ceremony (the word apparently meaning "festival of renewal"). Since she lives in London I was looking forward to her next concert, but according to her <a href="http://www.mitsukouchida.com/concerts.php">agenda</a>, she will have sooner toured the planet several times than perform again in the UK. Farewell Mitsuko!</div><div><br /></div>Maximehttp://www.blogger.com/profile/17820669704568697363noreply@blogger.com0tag:blogger.com,1999:blog-4785174943828024073.post-6752586170755837732009-06-07T10:34:00.022+01:002010-04-18T00:56:23.953+01:00La religion comme mise en abîme de soi-mêmeJe suis tombé sur la reproduction d'un tableau très étonnant:<div><div style="text-align: center;"><br /></div><div><img style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;width: 331px; height: 400px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg15teFWdht96Z5FtUALd2IISAytLy6df3f-ls53C831mq_BqoISQ7MNJmxgeRoycCLU6ZAYGzBZGMP2LZtyN_4wVvyplDMQl7s2cxJew1lYWZh_USWmTfjLzlHrK_gdNXaDK9406k_22z8/s400/SofonisbaAnguissola1556.jpg" border="0" alt="" id="BLOGGER_PHOTO_ID_5344517596954720786" /></div><div><br /><div>Ce qui a d'abord attiré mon attention est que je n'avais jamais vu un autoportrait de femme aussi ancien. <a href="http://en.wikipedia.org/wiki/Sofonisba_Anguissola">Sofonisba Anguissola</a> [Cremona, c. 1532-Palermo, 1625] l'a peint en 1556 -- seulement huit ans après le probable premier autoportrait féminin par <a href="http://en.wikipedia.org/wiki/Caterina_van_Hemessen">Caterina von Hemessen</a>, lequel est également le premier autoportrait (tous sexes confondus!) à représenter l'artiste devant son trépied. </div><div><br /></div><div>J'ai d'abord hésité quant au sexe de Sofonisba, étant donné que ce prénom est en soi déjà tellement étrange qu'il pourrait tout aussi bien être celui d'un homme, que son corset rigide ne laisse pas entrevoir sa morphologie, et que son visage pourrait être celui d'un jeune apprenti aux traits efféminés. Mon réflexe en cas de telles incertitudes est de lire quelques phrase du texte accompagnateur jusqu'au premier pronom "il/elle". Ca m'a pris un peu plus de temps que d'habitude: l'image issue du catalogue de l'exposition <span class="Apple-style-span" style="font-style: italic;">El retrato del Renacimiento</span> au Musée du Prado était accompagnée d'un texte en espagnol, langue moins portée sur les pronoms sexués que le Français (mais heureusement plus encline que lui à spécifier le sexe d'une profession: "<span class="Apple-style-span" style="font-style: italic;">la artista</span>", "<span class="Apple-style-span" style="font-style: italic;">la pintora</span>", etc.). Bref, Sofonisba est bel et bien une femme.</div><div><br /></div><div>Je me suis mis ensuite à admirer sa simple féminité sans artifices. Bien qu'elle ait embrassé une carrière habituellement réservée aux hommes, elle a su conserver une sensibilité de femme, enfantine et délicate. La grâce de ses mains et de son visage émerge de l'habit sévère qui cache ses formes.</div><div><br /></div><div><div>Je note en passant (franchement, excusations pour toutes ces digressions!) qu'il était inacceptable à l'époque pour les artistes femmes de s'exercer au dessin anatomique, qu'il était pourtant nécessaire de maîtriser pour pouvoir prétendre composer des oeuvres de larges envergures impliquant de nombreux personnages. Ca explique en partie qu'elles se soient rabattues sur les portraits, et en particulier les autoportraits. </div></div><div><br /></div><div>(Une tache vive de couleur magenta sur sa palette m'a fait sourire, parce que j'ai une théorie selon laquelle les adolescentes d'Oxford portent des vêtements de cette couleur le soir pour indiquer leur disponibilité sexuelle...)</div><div><br /></div><div>Mais mon enthousiasme a vraiment pété le plafond lorsque je me suis posé la question "mais que peint-elle?" Naïvement, le tableau nous montre Sofonisba peignant une scène religieuse , sans doute à usage dévotionel, représentant la Vierge et le Christ (ou, peut-être, à cause de l'attitude sensuelle des personnages, Aphrodite et Cupidon?). Mais à la réflexion, ce n'était pas une scène religieuse qu'était en train de peindre Sofonisba lorsqu'elle peignait son autoportrait (et pour cause), mais sa propre image: je crie à la supercherie!</div><div><br /></div><div>Si Sofonisba avait voulu peindre fidèlement ce qu'elle voyait, c'est-à-dire sa propre réflexion dans le miroir, ce qu'elle aurait peint sur son canevas aurait été une seconde reproduction d'elle-même en train d'en peindre une troisième et ainsi de suite jusqu'à l'infini. Ce procédé d'incrustation répétée <span class="Apple-style-span" style="font-style: italic;">ad libitum</span> dans une image d'une réplique d'elle-même au format réduit est une mise en abîme. Mais Sofonisba a choisi de remplacer ce puits sans fond s'ouvrant sur elle-même par une image pieuse. J'y vois un enseignement sur la religion:</div><div><br /></div><div style="text-align: center;"><span class="Apple-style-span" style="font-style: italic;">La religion se substitue à la limite infinie </span></div><div style="text-align: center;"><span class="Apple-style-span" style="font-style: italic;">de l'auto-représentation.</span></div><div><br /></div><div>Je trouve ça très intéressant. (On pourrait presque pousser jusqu'à y voir une manifestation du principe holographique...)</div><div><br /></div><div>Une interprétation alternative serait que Sofonisba, par le remplacement de sa propre reproduction par l'image religieuse, essaie d'exprimer qu'elle s'identifie à la Vierge -- un peu à la manière dont un bon chrétien est censé s'identifier au Christ et tâcher d'imiter sa vie. La croix que forment son pinceau et son bâton d'appui (comment appelle-t-on cet outil?) confirment cette lecture. Mais il faut admettre que c'est forcément plus compliqué, puisque le tableau que peint Sofonisba ne représente pas seulement la Vierge, mais aussi son enfant (voire même Aphrodite et Cupidon). S'il y a identification, ce n'est donc pas avec un seul, mais deux personnages bibliques (mythologiques). Elle s'identifierait avec quelque chose de plus abstrait, du genre de l'amour maternel (ou de la sensualité amoureuse).</div><div><br /></div><div><br /></div></div></div>Maximehttp://www.blogger.com/profile/17820669704568697363noreply@blogger.com0