Edward Witten

Today I was at the Festival of Mathematics 2009 in Rome to listen a talk by Edward Witten. Witten is one of the greatest living physicists and his contributions to mathematics were so relevant that he was awarded a Fields medal. This was for me a great chance to see him personally and hear at his way of doing physics for everybody. This is a challenging task for anyone and mostly for the most relevant personalities of our community. I was there with my eleven years old son and two of his friends. Before the start of the talk, John Nash come out near our row of seats and my son and his friends suggested to go to him asking for an autograph. Indeed, he seemed in real difficulty as some people was around him asking for an handshaking or something else. Somebody took him away and this was a significant help.

I showed Witten immediately at my company. He was there speaking and greeting people around. He appeared a tall and a very cordial man.

Marco Cattaneo, deputy director of the Italian edition of Scientific American (Le Scienze), introduced Witten with a very beautiful and well deserved presentation. Witten of course speaks Italian being his wife Chiara Nappi, an Italian physicist. Witten started to talk in Italian saying that he was very happy to be in Italy to meet his wife parents but his Italian was not enough to sustain a talk like the one he was giving.

The talk was addressed to a generic public. It was very well presented and my company found it very interesting. Witten did not use any formulas rather than Einstein’s and the parabola and this is enough to keep up the attention of the public for all the time.

Witten pointed out that quantum field theory represents the greatest achievement ever for physicists. This theory is so deep and complex that mathematicians still fail to go through it fully and most of these results, widely used by physicists, are presently out of reach for mathematical proofs. He also said clearly, showing it explicitly, that the problem implied in the vertexes of ordinary Feynman diagrams are removed by string theory making all the machinery less singular.

He did a historical excursus starting from Einstein and arriving to string theory. He showed the famous Anderson’s photograph blatantly proving the very existence of antimatter. A great success of the wedding between special relativity and quantum mechanics. This wedding produced such a great triumph as quantum field theory. Witten showed this with the muon magnetic moment, emphasizing the precise agreement between theory and experiment, but saying that the small discrepancy may be or not real new physics being just at .

He emphasized the long path it takes to physicists to achieve our present understanding of quantum field theory and cited several Nobel prize winners that gave key contributions for this goal. He pointed out the relevance of the seventies of the last century that become a cornerstone moment for our current view.

Starting from Gabriele Veneziano’s insight, Witten arrived to our current view about string theory. He said that this theory has had some frailty aspects that put it, sometime, on the border of a gulch. But, as we know, recoveries happened. He said that strings set the rules and not the other way round as happens with the Standard Model. He gave the example of the Veneziano’s model for strong interactions that was there pretending spin two excitations. This made the model better suited for other aims as indeed happened.

Witten hopes that LHC will unveil supersymmetry. He showed a detector of this great accelerator that we will see at work at the end of this year. Discovery of supersymmetry will be a great achievement for humankind as it will be the first evidence for a world with more than four dimensions. Anyhow, Witten said, string theory put out several elements, quantum gravity and supersymmetry are two of them, that make this theory compelling.

After the talk, some questions by the public were about ten or eleven dimensions in string theory. Witten avoided to be too technical. But the most interesting question was the one by Marco Cattaneo. He asked about critics of string theory and its present inability to do predictions. Witten’s answer was quite unexpected. He said that it is a good fact that a theory has critics. It is some kind of praise for it. But he also said, and his answer was quite similar to the one of Nicola Cabibbo, that there are a lot of things to be understood yet but such a richness physicists run into cannot be just a matter of chance with no significance.

Surely, this has been a very well paid waiting!

Nicola Cabibbo and Arno Penzias

Today I have been at Festival della Matematica 2009 here in Rome to listen at a discussion with Arno Penzias and Nicola Cabibbo.  The moderator was Riccardo Chiaberge, a journalist of the italian newspaper Il Sole 24 Ore. Chiaberge wrote a book with an interview to George Coyne and Arno Penzias (in Italian, see here). Cabibbo is currently the President of the Pontificia Accademia delle Scienze and is a believer. This evening he took the role Coyne had in the book in a confrontation between scientists with different beliefs. Asked by Chiaberge if the Pope listens Accademia, Cabibbo said “Sometime.” and cited the case of cerebral death.

Penzias has been put by Chiaberge on the Einstein side, a “non-believer deeply religious”. But what Penzias said has been sometime astonishing revealing a kind of faith elevating humankind well above its nature. Of course, themes like string theory and multiverse were also touched upon in the discussion. Cabibbo said that we should give time to the theory to develop before to conclude anything about, being now too early to draw any conclusion. Stringists will say but surely “mathematics is truly beautiful”. When he said so I thought to Perelman that, copying a functional from string theory, achieved one of the greatest goals of modern mathematics. Penzias is more skeptical about and does not think it should be considered science yet and, on the same line, multiverse is not falsifiable and so to be dismissed. Cabibbo said “till now!” letting us think that the future will deserve some surprise about as always happened in matters like these.

This point was quite entertaining as Cabibbo defended multiverse as the most elegant idea to explain the foundations of quantum mechanics but, as Chiaberge emphasized, this is an escape for atheist to claim the non-existence of God. On the other side, Penzias said that our current understanding of Universe and all this nice fine tuning of its constants appears a serious support for believers.

Galileo, Copernico and Kepler were discussed and the Galileo question, with his trial and abjure, was declared by Cabibbo as a severe error by the Catholic Church that cost too much to Italian science. He said that “Bellarmino, notwithstanding was a fine cultured man, failed to recognize that these were completely new matters” and should have been carefully treated.

About the question of intelligent design and Darwinism, Penzias put forward a nice metaphor. He remembered the last scene of The Wizard of Oz where a dog moves a curtain unveiling the wizard pushing around buttons all the time and this appears to be the god of intelligent design. On the other side, human beings are really cousins of chimpanzees but there is something more, that kind of inexplicable that makes us believe that something like love and free will are real as the rest of our physical world. Cabibbo added that the idea of evolution should enter into the certainties accepted by the Catholic Church as the Copernican system and all that. Evolution is an assessed fact but still some embarrassment is seen from clerics, the same that happens when one talks about the possibility of intelligent life in other solar systems. Giordano Bruno has not been fully digested by Catholic Church yet.

Cabibbo also put forward a nice analogy between phase transitions and the appearance of  intelligence in human beings that completely overwhelmed previous animal species, a threshold effect.

Chiaberge gave a nice summary of the discussion by saying:”Science has limits but no authority should impose limits on it”. All agreed about this but Penzias remembered horrors of some experiments and Cabibbo emphasized that for medicine some kind of limits should be eventually considered or, better, self-imposed.

Tomorrow I will be there to listen Edward Witten. Stay tuned!

Festival of Mathematics 2009

In this month will be held at New York and Rome the Festival of Mathematics (Festival della Matematica) 2009. It is an opportunity to hear Nobelists and Fields medalists talking about physics and mathematics. In New York there will be Shelly Glashow, Benoit Mandelbrot and Brian Greene. In Rome there will be John Nash, Arno Penzias and Edward Witten. I will take my chance to hear Witten talking. The argument of his talk is “Geometry and Quanta”. Penzias and Nicola Cabibbo will talk about “Thinking with Mathematics”.

The festival  is organized each year by Piergiorgio Odifreddi, an italian mathematician, to give the opportunity for people to get acquainted with mathematics listening some of the most relevant thinkers working in this field. This is the third edition.

Last year I listened John Nash and Robert Aumann and it was the chance to let my son know such great personalities in the history of mathematics and economy.