Nuclear Physics and the non-relativistic conformal fixed point and all that!

Nuclear physics is sometimes considered to be a dead subject sometimes, by some people. I dont think that is the case. Its merely not fashionable for many people. And why not? Maybe it does not have high sounding terminology embedded in it. Anyway, in this entry I will try to argue that it is indeed interesting,--very interesting; and some very cool features can be seen in it. Since I am not a nuclear physicist, my description will be rudimentary.
Lets come to the concept of non-relativistic conformal field theories. Suppose you have a set of fermions interacting with each other. Then there is a phase shift associated with the incoming and outgoing fermion wavefunctions. Now imagine, that the interactions between the fermions can be tuned by tuning some coupling, say the magnetic field. For strong coupling, the fermions could be bound into fermions, while for arbitrary weak coupling they would form a Cooper-pair type bound state. The scattering length changes sign in these two phases, and at the point of transition it diverges, giving rise to universal physics. Thats the non-relativistic conformal fixed point I was referring to.
Now about the nuclear physics connection. The nucleon-nucleon (N-N) scattering length is of prime importance in nuclear physics. For real world, its small and negative for the pion phase shift in a particular channel. It is believed that tuning the quark mass would change the sign of the pion phase shift! The quark mass plays the role of the coupling in the previous example.
I am not yet aware of the implications of this interesting phenomena, but I do intend to find out.
True, I have glossed over the details, but I will add a more complete picture as and when I get it.

While the renormalization issue in the Diffusion coefficient seems to have been sorted out to a large extent. my efforts at reweighting still seems to be unsuccessful. I refuse to believe that in a SU(2) theory I can't reweight beta's that differ by 0.02 from each other, whether in the confined or in the deconfined phase! The smearing business is coming out more or less okay: while I am not doing anything obviously wrong, I may not be doing enough to improve the results.
Today ran about 5.5 rounds in the Kohli stadium. Quite an achievement for me!
And what is going to happen about the screening-mass paper? And post-doc positions? Really, most annoying, not to know!

Ground and Scattering states

One of the things that I gained a bit more understanding of during the course of this Nuclear conference that is going on now is the issue of the scattering and bound states, which I am going to say here in a very hand-waving way.
The point is the issue that the S-matrix of a QFT that you calculate on the lattice is very different from the one that in continuum. For sure. But then, how can we get information about the continuum S-matrix. The seminal work of Luscher showed how this can be done. He argued this information lies in how the energy levels scale. If it is a bound state then there is scaling by exp(-m*L) where m is the mass of the bound state and L the lattice size. On the other hand, if it is a scattering state then it will scale by 1/L^3. Thus, a S-matrix with only poles gives the information about the full spectrum of the continuum theory with both the bound and scattering states. There's some bit about the momentum dependence of the phase shifts that come in somewhere, but I dont know that yet. Will hopefully learn that while doing this project with Nilmani, Anyi and Shailesh.

Another nice movie: Udaan. Watched it yesterday. Somehow it resonated with me for obious reasons. If only I could get free like that right now. But alas, no! Only an ominous patience for me.

the Harry Potter weekend

Saw the movie Harry Potter and the Deathly Hallow (the first part). A reasonable movie with nice sceneries that tried to remind me of the LOTR, with some success. This seemed to be a faithful reproduction of the book. But enjoyed it a lot!
Most of the weekend was spend doing rather useless work on making the web-page for a nearly finished project, and making tables in tex. Throw in a couple of fine lectures by Evgeny Epelbaum on the Chiral Effective Field theories, and there you have my entire schedule. The lecture was saturday was mostly on EFT with pions, which I have an idea of and could mostly follow. But on sunday, he described EFT for nucleons by integrating out the pion degrees of freedom: the procedure seemed very interesting, but I was unable to follow most of it. There is some effective range expansion that needs to be understood.
The lectures on Efimov effect also seemed very interesting---much to the extent of trying something in one of the projects I am doing!
Looking forward for a small break soon. Will let know if everything goes well.

Ramona and Beezus

If it does happen that you are feeling down and depressed, that sick feeling inside your stomach that refuses to manifest, Ramona and Beezus could go some way to comforting you. Nothing like Bridge to Teribithia, this one simply focuses on the lives of two sisters in mid-Western America and the people that matter to them. I went on waiting for something great to happen, some exciting and out of the place adventure to happen, but none did. It was ordinary, far too ordinary. But it wasn't until the end that I realized that among the ordinary was really hidden something extraordinary. The movie was timeless and placeless: you could have set the plot to be somewhere else and at some period of time, and yet it would be as good. Had I been in any other mood, I would have been ecstatic when the movie ended. I was too upset over something, but this movie went far to lift my spirits.
Of course, I have seen lots of movies better than this, but this had some quality to it that clicked at the right point of time at the right situation.

Hello after a long time

Quite a long time has passed: the QCD conference at the University of Calcutta is over (thankfully my talk went well!), the Durga Pujas have come and passed and so has my visit to home. I have finished watching most of the South Park episodes, which I think is a great achievement by itself! Have started applications for Post-Doc positions. Work going on for several projects! A rather strenuous time for me!
Will try to write more soon.