Cabibbo and quark mixing

16/04/2009

Today I have been at Accademia dei Lincei, a renowned institution located here in Rome. There was a talk by Nicola Cabibbo about quark mixing. This conference was addressed also to people not having a proper knowledge of physics, making quite exciting to listen. Cabibbo is member of the Accademia since 1973 and his groundbreaking discovery happened in 1963 (see here). There has been some fuss last year with Nobel prize awarded to Kobayashi and Maskawa but not to Cabibbo (see my post here). So, it was a chance to hear from his voice his personal recollections about all this matter.

He gave a historical overview about quark mixing and how he found himself on the right path. Then, he cited when, on 1963, he met Feynman that said him that things could not work as he got V+A in some cases rather than V-A. Indeed, confirmations arrived later.

Giorgio Salvini, an experimental physicist well-known for his contributions to high-energy physics, introduced Cabibbo recalling as, when in Frascati, after Kobayashi and Maskawa got published their paper, he hit his forehead saying “How did not I think about six quarks?”. Indeed, Cabibbo recalled when, in the sixties, he was in his office at Rome University “La Sapienza” and Shelly Glashow knocked on his door. Glashow asked to Cabibbo if his approach could be used to understand CP violation. At that time, Glashow was frequently in Rome and, some time after, he took Luciano Maiani with himself at Harvard and we all know as history went. To obtain CP violation from Cabibbo mechanism one should introduce a complex phase factor. At that time no more than four quarks were postulated. So, Cabibbo answered that was not possible as, whatever phase one introduces, this can be removed. With six quarks this is no more possible and so, he said, having not thought about six quarks, he missed in this way the possibility to uncover the full CKM matrix.

In the end of the conference, some questions were put forward and Cabibbo promised to put all the talk on paper, after Giorgio Salvini solicited him for doing this. I hope to read his paper. This is a must after such a beautiful talk.

Advertisements

The bet and the furious

15/09/2008

It is time to bet. There is a beatiful post by Jester with a lot of very interesting comments. Lubos has convinced Jester to bet about supersymmetry to be seen at LHC. What is really interesting is the definition of the terms of the bet. For details check the post above and the comments.

My grandpa used to say “always insist, never bet”, one cannot know how far a betting fever can lead you and your bank account. LHC, as I see it, is a Pandora’s jar. The opening is just a few months ahead.

Meanwhile Jester and Lubos are fixing the terms of the wage by email. We’ll wait and see.


A stunning summer

03/09/2008

It is customary for me, during my holidays, to read some technical books that I bear with me at Satriano, a small town very near Soverato. This summer I have read the book of Stephan Narison on QCD as QCD is currently my work and this is a really beautiful book. But I have written papers on almost all fields of physics and in the summer of 2005 I was struggling with general relativity. That year I took with me a wonderful book by James Hartle: “Gravity: An Introduction to Einstein’s General Relativity” . This book has been a source of inspiration for my work. Indeed, in a few days I was trying to apply my well developed approach for strong perturbations to Schwarzschild solution. This was a blind alley as I was manipulating an exact solution that has no much to say for perturbation techniques. As I looked at the problem more in depth, I was able to make this application to general relativity in a paper published on International Journal of Modern Physics D (see here for a preprint). I have to thank the editor Jorge Pullin for appreciating my work. I met him in Piombino at DICE 2006 Conference where he gave a very nice talk.

This paper has been a fundamental starting point for all my succesive work for two main reasons: Firstly, I have understood that to solve strongly perturbed partial differential equations one has to recur to a gradient expansion and secondly, this paper gives a sensible proof of the Belinski-Khalatnikov-Lifshitz (BKL) conjecture that permits to understand why near a singularity the space-time is homogeneous. Vladimir Belinski has been a professor of mine at University “La Sapienza” of Rome in 1992. He taught me general relativity with the more exotic solutions: BKL and gravisolitons. He is also well-known for having written down parts of Landau-Lifshitz book about this matter. I remember a nice talk with him in those days about BKL and for this reason I acknowledged him in my paper. Indeed, after speaking with him I should have been able to catch immediately the answer but times were not so mature and I have had to do a lot of work and thinking before to arrive at this successful point.

After understanding how to do strong perturbation theory to partial differential equations, my  next step was to find a way to generalize it to quantum field theory. In a few days I was able to do it and this became a paper for Physical Review D (see here for a preprint). In this paper I improve on the Bender’s approach (see here) obtaining the propagator and the spectrum for a massless scalar theory showing that in the infrared this theory acquires a mass gap. A real successful improvement!

After that stunning summer, I have been able to extend all this to Yang-Mills and QCD but we are talking about today…


Sean and Horacio

18/08/2008

I know Sean Carroll as some years ago I read his beautiful lectures on general relativity that become a book. Some years later I started to read his blog and this I do also today. Sean touched a lot of arguments in physics during these years but the most important for me are those about arrow of time and reality forming (measurement problem in quantum mechanics). These two matters are strongly linked and their understanding represents a great achievement in physics and this explains why a lot of ink, paper and digital data have been spent around the world. Sean has written an article on this on Scientific American (see here). Contrarily to some wisdom around this problem is really deep as there is no reason on Earth to accept environmental decoherence and multi-universe interpretation as the ultimate answers that finally do not grant any answer to a simple fact. This fact was explained to me quite simply by Giorgio Careri. Careri has been a professor of mine at department of physics of “La Sapienza” in Rome. A day I was walking to the new building of the department (Fermi building) together with some other students when we met him going into the opposite direction. I do not remember the reason why we started to talk but he said something I am still here to remember:”One of the deepest question physics should answer is why, having a four dimensional space-time, we can move backward and forward and we can stop in three of these dimensions but not in time?”. Currently an answer is still lacking being at the root of our understanding of how reality forms and the way it forms.

Horacio Pastawski is a researcher working at University of Cordoba in Argentina and has carried out with his a group a lot of relevant work that can be traced back on the most important archival journals in physics and on arxiv as well. Horacio’s group has found an answer to this matter through NMR experiments. The point can be traced back to the Boltzmann and Loschmidt controversy. In order to answer to the criticism of Loschmidt claiming that as all laws of mechanics are reversible one should conclude that H-theorem is false, Boltzmann put forward the so called Stosszahlansatz (molecular chaos hypothesis) to conclude that indeed H-theorem is right. Boltzmann’s hypothesis is purely statistical and being this true Boltzmann is right. So, the understanding of arrow of time passes through an explanation of Boltzmann’s Stosszahlansatz that we currently lack. But in 1998 Horacio’s group performed an NMR experiment with a complex molecule, ferrocene and cobaltocene, where they showed that an intrinsic instability appears in the thermodynamic limit provoking irreversibility (see here). This shows that Boltzmann is right and this also explains why we observe irreversibility all around in the macroscopic limit. Of course, this result met skepticism in the community and they had severe difficulties to get their paper published on an archival journal notwithstanding no flaw is appearing in their experimental procedure. Anyway, they published their results on Molecular Physics and Physica A and so these are part of scientific literature. But their results received an unexpected confirmation on PRL quite recently in a different perspective as these authors were trying to understand decoherence in quantum computation.

We see that thermodynamic limit plays a central role in our understanding of reality and this matches fairly well with the observed fact that macroscopic objects behave classically and gives also a satisfactory understanding of Boltzmann’s hypothesis that would be completely missing accepting acritically environmental decoherence and multi-verse.


A great intuition

11/08/2008

In the fall of August 2001 I was in Gargnano on Garda Lake in Italy to participate at the Conference “Mysteries, Puzzles and Paradoxes in Quantum Mechanics”. This was one of a series of Conferences with the same title organized by Rodolfo Bonifacio, a former full professor at University of Milan and now retired (latest news say that he is taking sun in Brasil). These Conferences were very successful as the participants were generally the most representative in the field of quantum optics and fundamental physics. I have had also the luck to meet interesting people that are still in touch with me like Federico Casagrande, an associate professor at University of Milan currently carrying on relevant research in quantum optics and laser physics. That year there was also Vittorio Giovannetti. Vittorio took a PhD in Physics at University of Camerino with Paolo Tombesi and David Vitali that are behind an international renowned group of quantum optics and gave also to the community a number of high quality researchers. At that time Vittorio was a post-doc at MIT and was working together with Seth Lloyd and another brilliant Italian post-doc Lorenzo Maccone. This collaboration produced a lot of relevant papers, mostly in applications of quantum mechanics, that appeared on Nature, PRL and several other high impact archival journals.

Bonifacio was involved with an original idea about intrinsic decoherence. He got a paper published on Nuovo Cimento B and another, with the collaboration of Camerino’s group, on PRA. After we listened at his talk about this interesting matter I exit the room where talks were taken place and exchanged some words with Vittorio and another person. In a while I averted my attention from Vittorio and the other person and started to mumbling thinking about decoherence. Than, looking at Vittorio I said loudly: “Yes, thermodynamic limit! Classical limit can be obtained from quantum mechanics much in the same way thermodynamics is obtained from statistical mechanics!”. Vittorio stared at me and repeated “Yes, thermodynamic limit.” than kept on talking with the other person. This was the start of a lot of papers I have got published on this matter and some interesting experimental work has also been done. The question is still open. The proceedings of the Conference are here.

Today there is a lot of confusion in physics about classical limit and interpretation of quantum mechanics. Indeed, there is a lot of people accepting without critics many-world interpretation without realizing that are out of the realm of physics in this case. If a theory has no criteria to undergo an experimental check is not a theory and we have to forget about this. I have seen a lot of unprepared people talking about many-worlds without elementary cognitions of physics. This is bad and this is why we are living this times today. Mathematics is not enough to be a physicist.


How good are you at solving equations?

01/07/2008

Sometimes one just looks back and some events appear revelatory with respect to what the future will deserve. When I was a student at University of Rome “La Sapienza” I had the luck to learn the best from some of the best Italian scientists. My course on mathematical methods of physics was taught by Giovanni Jona-Lasinio (yes, that Jona-Lasinio). A day he entered the room to start the lesson. That day he decided he wanted to see how good we were at solving equations. So, he wrote an integral equation at the blackboard and asked us to give the solution. I looked at the equation just a while and loudly claimed:”The solution is 1!”. Jona stared at me with surprise. At my left was sitting Andrea Crisanti. He is presently associate professor at that same university and has given relevant results in statistical mechanics. He exclaimed: “There are two ways to solve an equation: with method and with luck”. He did not say exactly “luck” but the vulgar word we use for this case that makes this sentence surely more entertaining. So, a posteriori, taking a look at my work I should say that this is my gift. All my work in physics is based on a completely new approach to solve differential equations. And yes, I am lucky, all laws of physics are written through differential equations…


%d bloggers like this: