Finally the day has come when the enthu people could find some common free time to sit together and watch the STRING THEORY lecture part 1 by Prof Shiraz Minwalla. This was not a new lecture video by the way, it was just taken from his TIFR webpage http://theory.tifr.res.in/~minwalla/ . Although these videos are accessible to all, Prof Ramadevi wanted us to sit together and watch such that if there is any doubt, students can ask her. It was however very difficult in the past to find a common free slot out of the tight semester schedule in IIT Bombay. But yesterday people agreed to come for it although it was a national holiday on the occasion of Eid. The first lecture was very elementary, he started with a little motivation for doing strings and then went on to discuss relativistic point particle action, the reparameterization invariance (under one to one mapping between 2 parameter space), use of lagrange multipliers in the action etc. He also made a gauge symmetry interpretation of the reparameterization invariance. I just had a small doubt if we can have a lie algebra kind of interpretation of this gauge symmetry like we have in our standard model of particle physics. Prof Ramadevi commented that this reparameterization is something more general (like a general coordinate transformation) and hence need no be specific to lie algebra. From non-academic point of view also it was enjoyable, you can guess the reason if you are aware of Prof Minwalla's body language..:P. We are planning the screening of his second lecture next week. Hope to see more people there than yesterday.

## Tuesday, September 22, 2009

## Thursday, September 17, 2009

### Guns n Roses coming to India in November...will it rain??

What can be more awesome for all the music crazy Indians than this!! When one of my friend told me about it I thought its a rumor. But its certainly not. Just saw in economics times that GnR is coming to rock India in November 2009. The link to the newspaper article is http://economictimes.indiatimes.com/News/News-By-Industry/Media-/-Entertainment-/Entertainment/Guns-N-Roses-to-rock-India-in-Nov/articleshow/4997070.cms

No matter in which city they perform in India, it will definitely be the biggest loss if you don't watch them live. So don't miss the fun!!
## Saturday, September 12, 2009

### Oops!!...my model violates R-parity

Yesterday I got a very important remark on the paper I am writing from my supervisor. He mentioned that some of the terms in the lagrangian violates R-parity. By the way R-parity is a discrete symmetry defined as $ R_p = (-1)^{2s+3(B-L)}$ where s is the spin, B and L are baryon and lepton number of the particle respectively. Although in the model there is an overall B-L gauge symmetry, there arises R-parity violation in some mass terms. These mass terms however are not coming from the soft SUSY breaking lagrangian, but from the superpotential itself. The mass lagrangian actually mixes two different fermions with odd and even R-parities. However there is no vertex (as far as I know) in the model which leads to R-parity violation and hence I don't think these R-parity violating mass terms would lead to any dangerous proton decay type of consequences. I am still waiting for supervisor's comments on this. I hope it will be enough to mention this in the paper without exploring further details. Just keeping my fingers crossed...:)

## Wednesday, September 9, 2009

### Two talks by Dr. Rishi Sharma (Los Alamos National Laboratory)

Dr Rishi Sharma, an IITB Physics alumni came to the department yesterday to give a talk on Superfluid heat conduction in neutron star crust. I could not understand most parts of the talk since there were many things which I am not familiar with. But today he gave another talk which I found very interesting. It was about application of AdS-CFT correspondence in hydrodynamics which is pretty interesting from relativistic heavy ion collision point of view. Although I don't work on string theory, I had some qualitative knowledge about AdS-CFT and all. But I never saw how it can be used to do some real-life calculations. Today Dr. Sharma spent a lot of time on it to show how it can be used to calculate shear viscosity which otherwise is not possible using perturbative QCD. He basically considers a N=4 Super Yang Mills theory in our world with number of colors very high, maps this theory into type II B string theory in 10 dimensions. He calculates the required partition function and all in a classical supergravity theory in a AdS5 spacetime and by this AdS-CFT duality we can use to same result in our world also. According to him this was the first application of AdS-CFT to so called phenomenology. The reference he has given are http://arxiv.org/abs/hep-th/0104066 and http://arxiv.org/abs/hep-th/0405231. He is also planning to give this second talk in TIFR today.

## Saturday, September 5, 2009

### APS (Annual Progress Seminar) Over on 2nd Sept...What a Relief!!

Finally its over, the annual progress seminar of my first year of PhD. I was of the opinion that like our seniors it would be in January next year. But the department has changed it and decided to have our APS in autumn semester only. The funny thing was we were informed less than one week before that we would have to give APS. Thank god, I already had made some write-up of my work and hence it did not take more than two days to make my report as well as presentation slides. The seminar also went well. The funny thing about it was that my PhD advisor was not present there...:P... So basically I had to defend myself all the time. I got confused when one examiner asked me the question how the soft SUSY breaking lagrangian differs from the other parts of the Lagrangian. I said it contains the mass terms of gauginos as well the superpartners of quarks and leptons. Then the examiner said the main difference is that this lagrangian is not invariant under SUSY transformations and each term in that lagrangian contains 2 fields multiplied by a dimensionfull parameter. I think I knew this before but somehow could not say it when I was asked. Anyway overall it was good which is a great relief for me.

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