30 June 2006

O carro de som da USP

Uma das piores coisas que existem na USP é o carro de som do SINTUSP, o sindicato dos trabalhadores da universidade. Com greve ou sem greve, quando menos se espera, ele aparece fazendo suas pregações por mais uma greve ou por melhores salários ou por melhorias na educação. Entretanto, o volume extremamente alto e a voz estridente e irritante da "tia da greve", a locutora oficial do carro de som, interrompe aulas e impede o trabalho de professores e funcionários.

Um grupo bem humorado de estudantes da Poli fez um video durante a pseudo-greve do ano passado. Lembro-me bem que houve um tumulto na Poli e o SINTUSP acusou professores da Poli de agressão. O video é bastante revelador e engraçado. Veja A Greve do Veto. Bom divertimento.

(Grato ao Oscar pelo link do vídeo)

Effective Field Theories

There is nice review on effective field theories, by C. P. Burgess, even though the title, Quantum Gravity and Precision Tests, does not reveal it. It starts with a scalar field theory and shows how to get the effective theory for the light modes. The great advantage over other papers is that it does not pay attention to the technicalities but rather to the ideas involved. It is ideal for those who are starting to study the subject. Of course, once you get this bird eye view of the subject you must then work out the technical details looking at other papers in the reference. The second part, which is much shorter than the first one, is dedicated to show how quantum effects can be computed in general relativity even though it is not renormalizable. It is really a good starting point.

23 June 2006

Strings 2006 - Day 5

Today is the last day I will blog from Beijing even though there are 5 more talks programmed for tomorrow. We again had 11 talks today. The more interesting one was given by Kapustin. He detailed a little bit the first two points of his work with Witten on the Langlands program. Gauntlett gave a nice review on Einstein-Sasaki and presented his new solutions for AdS_3 in 10 and 11 dimensions. Horowitz talked about a black holes and how tachyons are related to the evaporation process. And that is it. I am really tired and this last post is written telegraphically. I also lost my voice almost completely because of the air-conditioning. Hope Varig still has its planes flying otherwise I may stay in Germany for a while.

I just heard a rumor that CERN will not host Strings 2008. It will be postponed by one year and Rome will take it in 2010. I don't know the reason and maybe it is still the same: if supersymmetry is found in 2008 then we all will be together to celebrate it and if it is not found we will be together for a collective suicidal.

22 June 2006

Strings 2006 – Day 4

Yesterday I wrote that an alternative B. Greene gave a talk on cosmology at Strings 2006. In fact it was Koenraad Schalm who gave the talk. He belongs to the group of the real Brian Greene at Columbia. So what happened is that when I arrived the talk had already started. I went to the back of the room because the air-conditioning is better there. From there I could see that the speaker was not Brian Greene. He looked like Koenraad but it couldn't be him. After all, I met him when he was at Stony Brook and we discussed some calculations involving path integrals and anomalies. And this talk was on cosmology! Definitely it couldn't be Koenraad. So I was taken by surprise when he told me this afternoon that he had given the talk. He also commented that when he started the talk he said he was giving the talk in the place of the real Brian. I really have to change my glasses before I get into trouble. I mentioned Koenraad talk because it was really good. And now knowing that he went to cosmology makes it more valuable. Congratulations Koenraad and sorry for not having recognized you.

Besides that today was a heavy day. We had 5 talks in the morning and 6 in the afternoon. It is too much! Shiraz Minwalla gave an energetic talk as always. He reviewed the calculation of the partition function of N=4 gauge theories for 1/8 BPS states and the connection with giant gravitons. The next talk was by Schnabl and he described his solution of the open string field theory and the new advances. M. Green gave a nice talk about the new results for the four graviton amplitude. Stephan Hawking talked about the semi-classical birth of the universe. At the end there was a question and it took several minutes before he could make his computer answer it. It was a bit embarrassing. Some of the other talks were about emergent geometry and stringy phenomenology. The banquet at night was uneventful. Tomorrow there will be 11 lectures again. I will probably skip some of them.

21 June 2006

Strings 2006 – Day 3

In Toronto last year there was a nice talk by Albert de Roeck from CERN, about the LHC and how it could find signals of string theory like extra dimensions, mini black holes, and so on. This year B. Greene (not the author of The Elegant Universe) did the same with cosmology. In a very optimistic tone he said that stringy effects could be found first in cosmology rather than in particle physics. It is nice to see that some people are really worried about the gap between theory and experiment in string theory and are trying to fill the gap. It is really important that this sort of work be done since all experiments are dedicated and the experimentalists must know where to look.

Another very interesting talk was given by Staudacher. He gave a nice review about the status of anomalous dimensions in QCD and N=4 gauge theories, integrability and string theory. At the end he remarked that transcendentality may not be fundamental after all.

In the afternoon we went to the Great Wall. It is quite impressive. I can show you a picture but the real thing is much better.

In the evening we had Chinese opera. Very nice. Of course, most of the participants didnÂ’t understand the singers but the visual was magnificent.

On the commercial side, the Becker sisters and Cambridge were promoting their new book, co-authored with John Schwarz String Theory and M-Theory which will be released in November. There is a 20% discount for the conference participants which pre-order a copy. Also, there was a CUP stand during the first two days trying to sell specially string books. Today there was a stand of a bookshop selling CUP books which were specially produced for China. You could find Weinberg's book on QFT or Polchinski'’s book on string theory by about 10 dollar each volume. Who can compete with China in this way?

UPDATE: Dear Peter, see what happened with the alternative B. Greene in the next post: Day 4.

UPDATE: Dear S. Chan, I think prof. Yau is doing a great job in China. He participated in the solution of one of the greatest mathematical problems and brought two new institutes to China among other things. I have never attacked him. If fact I am surprised to know that China has such a tradition in mathematics. All this is very positive to science in China.

20 June 2006

Strings 2006 - Day 2

Today there were many talks and I will comment on some of them. For the full list see the program. The first talk was given by Maldacena and was about giant magnons. Since there is a believe that the N=4 supersymmetric gauge theory is integrable there is a lot of activity trying to show that using the AdS/CFT correspondence. For the moment you just find some sector of the gauge theory which can be mapped to a spin chain and look for the corresponding string theory hoping that you can gain some understanding for the full theory.

Feng gave a interesting talk about dark matter and supergravity. After presenting arguments that DM could be composed by gravitinos he said that the LHC could produce long lived sparticles that decay into gravitinos. These sparticles would then be stored in a tank of water and the gravitino properties studied. That is fantastic. Not just susy would be found at LHC but also supergravity! Freedman, Ferrara and van Nieuwenhuizen, who have just won a prize from the American Physical Society for the discovery of sugra, must be very happy.

Herman Verlinde showed how to do string phenomenology bottom-up. Just moosify the standard model. In the panel discussion that happened yesterday he suggested that all smart string theorist should be doing phenomenology because the LHC will start soon. He has a point. We have to understand what will come out of the LHC. But I don't believe many people will change as he changed. Each one has his own recipe for success.

Another good talk was giving by David Tong on how to use string and D-brane techniques to understand the quantum dynamics of field theory solitons.

To those interested I can not google or access wiki in any language.

Tomorrow there will be a tour so there will be fewer talks.

Almost forgot, after dinner we had a special seminar by Yau telling the history of the Poincaré conjecture and how he solved it! Again, high school students in the audience but less than in the Great Hall of the People yesterday. Also a video from Hamilton, a mathematician who participated in the solution, telling Yau's contribution to maths. Quite impressive that China has such a tradition in mathematics. And for the Chinese students, sitting among the scientists of the West, it must have been wonderful to hear that his teacher solved such an important problem. Looks like China soon will take the lead also in mathematics.

UPDATE: I can't answer any comment because I can't access blogspot. So I will answer
Peter's question here. Yau gave a public lecture not a technical one. He mentioned several other mathematicians which also gave contributions to the conjecture and explained what they did. He is not claiming that he did it by himself. I am not an expert on the conjecture so I don't know how fair he was in the lecture. But you know, it was a public lecture and Yau is now regarded as a sort of a hero by the Chinese.

19 June 2006

Strings 2006

That is amazing! I can't access my blog (or any blog at blogspot) from Beijing but I can write a post! Probably because to write a post the address is different (blogger instead of blogspot). So let us see for how long I can write. Also, no wireless is available making things more difficult.

Strings 2006 started with 3 public lectures in the Great Hall this morning. The very same place where the communist party holds its meetings. It is quite an impressive building! Besides the string conference participants the place was completely full with high school students. Around 3000 people altogether! The Chinese are investing heavily in education and also getting money from abroad. Two new institutes are being built in China with private donations! And if China gets the international linear collider it will soon became the leader in HEP. No doubt about that.

The first to speak was Gross with a popular talk on strings. The next one was Strominger and surprisingly he started talking in Chinese. The Chinese students liked a lot. He then turned to English to deliver the talk. He presented many cartoons to explain strings and black holes. I was told that he spent one year in China when he was young and then learnt Chinese. That may explain one of his cartoons where he put G. Bush near a black hole to illustrate that everything that goes inside the black hole falls in nothingness. The last lecture in the morning was given by Hawking. Complete chaos until everybody got a picture from him. Then he talked about cosmology and the big bang. No questions were allowed since it was late. Students were asked to write questions which will be answered on Wednesday. The authors of the selected questions will be able to have a picture side by side with Hawking! That is the way to attract young minds to science in Chinese way!

In the afternoon the first lecture was given by Witten on the Langlands program. Essentially the introduction of his 250 pages paper. At the end just one question, whether it could have any application in physics. Witten said that there is an application in his paper. Then Vafa talked about the swampland but nothing new was announced. The next two talks, by Shih and Intriligator, were about the metastable vacua in susy theories. Really nice talks. Then Ooguri talked about the possible uses of the metastable vacua in the landscape. And the final talk was by Yin.

In the evening we had the panel discussion with 13 people. Strominger was chairing it. No real debate. Too mild. Some interesting questions but none of them provocative enough. No discussion on the landscape either. Toronto was much better...

12 June 2006

José Leite Lopes dies in Rio

José Leite Lopes died today in Rio. He was 88 years old and sick. He had a prominent role in several aspects of physics in Brazil. You can read more at CBPF, the last institution he belonged to.

08 June 2006

A educação e a eleição presidencial

Como sempre, às vesperas de qualquer eleição, há uma disputa acirrada sobre feitos e omissões de governos presentes e passados. O governo Lula tem aparecido muito na mídia, criando universidades federais, dando aumento salarial ao funcionalismo federal (professores universitários incluídos) e apoiando explicitamente a ciência e tecnologia através de verbas (e corte de verbas) ao MCT, Finep e CNPq.

Na área da educação, os feitos estão sendo contestados pelo ex-ministro Paulo Renato Souza em Informe-se, presidente, publicado no Estadão. E ele apresenta números que são difíceis de serem ignorados por qualquer pessoa instruída. O atual ministro deveria responder, com números também. Igualmente bom seria que algum ex-ministro de CT comparasse os 8 anos de FHC com os 4 de Lula. Isto pode decidir o voto de muita gente. Ou não.

06 June 2006

Desenho animado

Via blog do L. Motl encontrei um link para o Google Video com um desenho animado sobre a experiência da fenda dupla. É bem introdutório mas vale a pena assistir. É recomendável ter banda larga.

05 June 2006

Is the Pioneer anomaly real?

Pioneers 10 and 11 were launched in 1972 and 1973 to study the outer solar system. In the late 70's small deviations of their trajectory were used to try to spot new planets. Instead of finding small forces pointing to the outer solar system it was found a force pointing to the inner solar system as if the gravity from the sun were a little bit stronger. This is the Pioneer anomaly. Many people think the drift is due to a malfunction of the spacecrafts or due to some trouble with the tracking stations on Earth. Others think some new physics may be at work.

What I did not know was that the data which gave rise to this finding was collected from a small part of the trajectory. The Pioneers have been flying for more than 30 years now but the anomaly data cover 11.5 years for Pioneer 10 and 3.75 years for Pioneer 11. A new article in New Scientist Have we got gravity all wrong? (unfortunately you need a subscription) tells the full story. Now people are collecting the old magnetic tapes and floppy discs containing all the 30 years of telemetry data to try to reconstruct the full space mission!

If the anomaly is real there is a proposal to launch a dedicated spacecraft to measure the effect between 2015 and 2025. Meanwhile it is better to keep a close eye on the trajectories of the next satellites going to the outer solar system.

04 June 2006

Café Filosófico

Não assisto TV regularmente mas em alguns domingos à noite tive a sorte de ver parte do Café Filosófico, um programa da TV Cultura de São Paulo que vai ao ar todos os domingos às 22 hs. Um programa decente num horário decente.

Hoje o psicanalista Jorge Forbes falou sobre "Um Amigo para Decidir". A conversa foi essencialmente sobre a importância que um amigo tem no encontro de nós mesmos, e como ele aceita e nos ajuda a definir e a contornar as esquisitices que todos nós possuímos. O interessante é que Forbes colocou muita coisa de um ponto de vista histórico e, diferententemente da maioria dos intelectuais brasileiros, está ciente do papel da globalização na nossa vida. Em particular, citou que a onda de blogs é apenas uma consequência da globalização. Todos agora podem colocar suas esquisitices para fora através de um blog. Muitos fazem dos blogs um diário enquanto outras o utilizam para deixar registrado as opiniões que não são aceitas no meio em que a pessoa vive. Retrato fiel do que acontece!

Numa outra oportunidade lembro-me de ter visto Renato Janine Ribeiro, professor de ética e filosofia política da USP falando sobre a liberdade e a insegurança. Foi uma conversa de assuntos antigos e modernas mas de um ponto de vista bastante abrangente, além de ser bastante informativa.

Realmente fico surpreso ao ver que existem intelectuais atualizados, atentos ao mundo que os rodeia e cujas fronteiras vão muito além das fronteiras brasileiras. Muito diferente de outros intelectuais alienados que se negam a aceitar a realidade, como Marilena Chauí, ou outros "filósofos" e "cientistas" conhecidos por estas bandas.

Só espero que TV Cultura mantenha a qualidade dessa série de programas e continue trazendo convidados capazes de falar de temas contemporâneos e de suas consequências para a nossa sociedade, sempre de uma perspectiva moderna e inseridade no mundo em que vivemos.

02 June 2006

Livro de Peter Woit

O livro de Peter Woit, "Not Even Wrong", foi lançado na Inglaterra e em breve será lançado nos EUA. Como todos sabem, ele mantem um blog no qual faz críticas à teoria de cordas e o livro segue o mesmo caminho. Li uma versão do livro de 2005 e não sei o quanto ele mudou. Assim como no blog, as críticas contidas no livro não são de cunho científico. Ele reconhece que não existe nada de errado com a teoria de cordas enquanto teoria, isto é, como uma construção que é matematicamente consistente. Sua crítica é que a teoria de cordas não produziu nenhum resultado que possa ser testado experimentalmente. E aqui estamos em terreno pantanoso. Eu, em particular, não vejo nenhum problema em se estudar uma teoria que ainda não fez contacto com a experiência. Outros acham inaceitável estudar algo desse tipo. É uma questão de gosto dedicar-se ou não a uma atividade desse tipo. Einstein demorou 10 anos para construir a relatividade geral sem nenhum input experimental. Ele queria apenas conciliar a gravitação com a relatividade restrita. A teoria de cordas é muito mais complexa que a relatividade geral (de fato a teoria de cordas contém a relatividade geral) e não é surpreendente que seja necessário muito mais tempo até termos a teoria completa.

A afirmação constante de Peter Woit de que a teoria de cordas não produziu nenhum resultado também não é completamente correta. De fato, ela ainda não fez nenhuma previsão experimental. Mas fez previsões teóricas que foram confirmadas. Através da correspondência AdS/CFT é possível estudar o regime de acoplamento forte de algumas teorias de gauge. Dessa forma, é possível prever o comportamento de certas quantidades nas teorias de gauge utilizando a correspondência. Esses resultados foram posteriormente confirmados através de cálculos na teoria de gauge. Eu acho isso simplesmente fantástico, dando uma credibilidade muito grande à correspondência e à teoria de cordas. O blog do Peter anunciou o livro e abriu espaço para comentários. Claro que o Lubos Motl já fez um review do livro no site do Amazon.com. A discussão entre os dois no blog do Peter está acalorada, como era de se esperar, mas não acrescenta nada de novo. But it is fun!

01 June 2006

Buracos negros

Uma apresentação multimidia muito boa sobre buracos negros pode ser encontrada aqui. Voce pode procurar objetos no céu em várias bandas de luz, visível, raio-X ou rádio. E depois fazer uma viagem a um buraco negro. Muito bom. Conexão rápida à internet é recomendável. Boa diversão. (Via Dynamics of Cats)