Sunday, May 30, 2010

Trying my hands on Volleyball for the first time :)

As far as I remember this is the first time I played Volleyball. I did not find it as boring as I had imagined. I always enjoyed playing cricket, football and badminton, but never thought of playing Volleyball. In fact I was very much pissed off when people in PRL talk about volleyball every time. It seems to be the most popular sports here and no wonder a sports-freak like me had to try it one day. I played three games continuously and it was not as tiring as football or badminton is . May be after practicing for one week, I will learn it more. Its all about proper timing and placement of the ball inside the court, not so difficult :)

Wednesday, May 26, 2010

Towards a more and more complete endless journey it seems!

The hunt for a complete fundamental theory of Physics is not new, it was one of Einstein's unfulfilled dream or may be many Great minds also dreamed of it earlier. Of course it sounds so amazing that just one theory could possibly explain everything around you, but sometimes I feel if this expectation or dream is just a wish or is there any physical necessity. I mean why can't we describe two different observed phenomena using two different theories. Yes we can, but there is no guarantee that these two observed phenomena always happen separately. There may be some situations where both these phenomena are happening simultaneously (in a non-independent way because the two different systems may interact with each other) and we have no clue which theory we should use to describe them. Hence we always wish if we had a theory which can explain everything using one master equation, say. But the question is how far have we been in this really long journey of four or five decades. String theorists are doing a great job of course in developing such an elegant theory which can describe all the four fundamental forces(gravity, electromagnetic, strong and weak nuclear force) in the Universe together. There is no other theory where we can talk about all four forces. In particle physics we can talk about the later three using gauge theories, but gravity is a real bitch in such theories which (if we include) make everything meaningless. Particle physicists that's why live with these three forces only which serve their purposes also because within the region of their interests gravity is negligible. So in particle physics, a complete theory means a theory which can describe these three forces together, the so called Grand Unified Theories (GUT). There have been tremendous works in the last three and half decades on these theories. They look beautiful of course since they have strong predictivities. You write your GUT theory at very high energy and see what it predicts at low energy accessible to experimental detection. There are many models based on different gauge groups which can give rise to standard model of particle physics at low energy and also predict most of the experimental results so far. The best thing is that you start with a theory where there is only one force, only one type of particles at very high energy, and as a output you get a theory with three different forces and many different particles at low energy. But still lots of works need to be done to have a complete theory. Although the achievements in both string theory and such GUT models are tremendous so far, I am still confused whether the real goal of having such a fundamental theory is achieved (even partially) or not. Like GUT people do not talk about gravity, string theories also do not uniquely predict the observed phenomena at low energy. Recently there have been lots of enthusiasm in arriving at a GUT model starting with string theory. But to make the theory internally consistent the GUT models or any particle physics model people arrive at from string theory constructions contain many more particles than a minimal particle physics model. Thus predictivity is lost if we consider such non-minimal models. Hope people will continue such works with more and more enthusiasm and soon we will see some success in this direction.

Saturday, May 22, 2010

Kites@Saturday 9 AM show

We went for Kites in the morning today. It got released yesterday. Although it got lots of hype but I was not having any expectation from it. I just went to spent 3 hours in an air conditioned theater away from Ahmedabad heat which has claimed couple of lives so far. And the best thing is it costs just forty bucks. Well the movie was neither too good nor too bad. The storyline of course was very weak, but the music, the cast, the choreography, the cinematography was very cool. Some of the locations in the movie were much much better than most of the hollywood movies. And the bollywood debutant Barbara Mori also did a much better job than many famous bollywood actresses without speaking a single Hindi word. Hrithik also did a great job which showed his dedications. If the story line had been strong, this could be the best movie of the year.

Friday, May 21, 2010

Assuming Survival principle was not a very good idea

I was doing some calculations regarding renormalization group evolutions of masses, couplings etc within the framework of a model. For simplicity I took the mass of various Higgs fields same as their mass terms appearing in the superpotential. After doing all the analysis, I came to know that the physical masses of the Higgs fields need not always be same as the bare mass terms in the superpotential or the Lagrangian. In fact the assumption I took was quite ad hoc. Before calculating the physical masses of all the Higgs fields, I can not assume their masses, but that's also one way to study the RG running, but it might not give the correct result always. In some cases the physical masses comes out to be very different from the bare mass terms and hence will affect the RG substantially. What happens is that when we write the F-term scalar potential of a model, sometimes the quartic term of a scalar field remains absent because the corresponding trilinear term was not there in the superpotential so as to obey the internal gauge symmetries. Thus the mass terms remain arbitrary at the renormalizable level and higher dimensional terms have to be considered. This leads to lighter Higgs masses than the bare mass terms. And even if the quartic terms are there in the superpotential, it is not to straightforward to say that the mass will be same as the bare mass terms, because the various Higgs fields mix with each other, and it's not unusual that the diagonalization of their mass matrix will give a small eigenvalue. So better calculate the physical masses of all the particles (not just fermions ) and then proceed with the RG evolutions.

Saturday, May 8, 2010

Micromega 2.4 is awesome!

Recently the micromega developing group has come up with its latest version 2.4 where they have included some really useful subroutines to calculate various other things which were not there in the previous versions. To tell you what micromega is, its a publicly available numerical package based on fortran and C, which calculates the relic density of dark matter in any supersymmetric model with conserved R-parity. In version 2.2 which I used last year, I could calculate the relic density , as well as the branching ratios of dark matter self annihilations as well as co-annihilations into various standard model particles, and direct detection rates etc. The best thing about micromega I found was the option of incorporating any supersymmetric model. Last year I was trying to use it for supersymmetric left-right model. Last year I was dying to study some particle physics models from dark matter indirect detection experiments point of view, that is , I wanted to know whether a particular dark matter candidate in my model can explain the anomalous positron excess over antiprotons found in various indirect detection experiments like PAMELA, FERMI etc. But when I came to know that for that I need to use both micromega as well as another package called GALPROP which basically studies the cosmic ray propagation, I gave up. But last month the micromega group has come up with something is a combination of earlier micromega and the GALPROP. Its really exciting to me since now I can incorporate any model into it and study it from indirect detection experiments point of view. I run it yesterday for the MSSM, and the output I got contained relic density, branching fractions of Dark matter self as well as co-annihilations and more importantly flux of positrons, antiprotons and photons. Although the plots of positron did not give any kind of peak (which PAMELA observed), as its the case for usual dark matter candidates in MSSM, but may be some other models will give rise to a desired peak. This will anyway decrease the amount of work a theorist have to do, now we don't have to write long programmes for the calculations , just write the .mdl files for a particular model and put it inside micromega and test the model against the indirect detection experimental results. Kudos to micromega developers..keep it up!

Wednesday, May 5, 2010

The Dead Man's running :P

For last couple of days I was trying to see how the Yukawa (The dead man :P) couplings of a particular model run under renormalization group evolution. Although at one loop level the equations are pretty simple, the whole sets of equations look messy since they are coupled to each other. So if there are say 23 parameters, there will be 23 coupled linear differential equations. For a complicated model where there are many parameters, lots of approximations need to be taken since we don't have as many input parameters at the electroweak scale. That's why I believe top down approach is much simpler although I never tried that. I always follow bottom up approach where I give low energy parameters as input and predict the high energy parameters. In top down approach since there are very less number of parameters, we can choose them so as to arrive at the low energy expected parameters after the running. Since I don't yet know the high energy theory properly, I can't say whether the high energy parameters I am getting after the running will fit inside a specific GUT model. May be it's time for me to switch to hard core GUT models and use the top down approach :)

Sunday, May 2, 2010

The Kasab behind 30-10@Guwahati got arrested!

Today I got the news of the arrest of NDFB( National Democratic Front of Bodoland) supremo Ranjan Doimary in Bangaladesh. He has been handed over to the Border Security Forces (BSF). This person was behind the deadly serial blasts in Guwahati (30-10-2008) just one month before the Mumbai 26-11 attack. The blast killed around 120 people injuring many others. It's been more than a year Kasab, the only arrested terrorist behind 26-11 attack has not received the punishment he deserves. I heard that may be tomorrow he will face the verdict. The announcement of verdict however does not guarantee punishment because of so many loopholes in the judiciary system. Anyway coming back to the Kasab behind 30-10 attack, I am afraid if I can call him a terrorist. Somehow Indian citizens who spread terror among people are called extremists, freedom fighters, maoists, naxalites etc etc. Even though this man is caught recently, I doubt what kind of punishment he will be awarded. Most of the time such "extremists" spend few years or months may be in prison and then even are allowed to contest in elections. No matter with what motivations they started their so called struggle, killing innocent civilians can not be justified at any cost. But in India, nobody cares about civilian's life. The Mumbai 26-11 attack gained so much attention just because of the foreign citizens who got killed. We must need a better judiciary system to prosecute such mass killers. I hope India will start handling these internal terrorism issues more carefully, because they pose a much bigger threat to the integrity of the nation than outside elements.