মোৰ বাবে আনে লিখা এটি কবিতা ২.....

তুমিয়েই কৈছিলা তুমি হাঁহিলে মই হাঁহিম
তোমাৰ বেদনাত মই কান্দিম
চকুত চকু থৈ একেলগে বাট বুলিম
তোমাৰ হৃদয়ৰ প্ৰতি স্পন্দনত মই থাকিম
তুমিতো কোৱা নাচিলা মই তোমাৰ জোনাক মচি অমাৱস্যাৰ চাদৰেৰে ঢাকিম
দুখৰ কৰণিত ডুবাই ৰাখিম
তুমি হয়তো বুজি উঠিছিলা তুমি নোহোৱা নিশাৰ বেদনা
চকুৰে স্পৰ্শ কৰিব নোৱাৰা মাথোঁ মনেৰে অনুভৱ কৰা এটা এটা নতুন পুৱাৰ ঠিকনা

Today's Seminar by Dr. Arunansu Sil (CEA/Saclay)

Today there was a good seminar in the department. Well, by "good" I mean a seminar related to some field which I truly appreciate. I know I am very biased in saying that, we should appreciate any scientific work no matter what field it is. Anyway coming back to the main point, the seminar was given by Dr. Arunansu Sil, a post doctoral fellow in CEA, Saclay. He talked about his recent works with his collaborators on Inflation and Supersymmetry Breaking. I will just state the main points which I can recall or may be I could understood from the seminar:

1. To explain the slow-roll inflation as well as the origin of quantum fluctuations at the reheat temperature T_R which gives rise to temperature anisotropy in the CMBR they have introduced a new approach incorporating supersymmetry.

2. The inflaton field couples to the supersymmetry breaking sector and its couplings to the MSSM sector is higly suppressed so that quantum corrections don't destroy the slow roll behaviour.

3. Then he discussed the various possible mechanisms of SUSY breaking and also introduced the famous ISS (Intrilligator-Seiberg-Shih) model of dynamical SUSY breaking.

4. Then he used inflaton field as well as the so called "waterfall" field ( I have no idea about the origin of this name) and the interaction of the inflation and SUSY breaking sector via gravity.

5. He showed that such scenario can lead to a long-lived metastable non-SUSY vacuum which could be the true vacuum of our present Universe.

6. He also talks about a distorted version of ISS model where gauge mediation is considered responsible for SUSY breaking. In that case the reheat temperature comes out to be of the order of 1 TeV whereas in the previous case (gravity mediated) it was of the order of 10^9 GeV.

I could not fully understand since I am not familiar with dynamical supersymmetry breaking as well as SQCD where he considered various accidental non-abelian global symmetries which gives rise to an SQCD duality (It basically makes possible to study the theory in both infra-red as well as Ultra-violet limit). Details of his work can be found in the references : Physics Letters B , 660, 236 and JHEP 0904, 092.

Hike in Stripends for UGC research scholars...:)..:D

(Click the image to get a better view)

Got Enough Reasons to become a Prof ??

I have just found this pretty cool graph in GraphJam.com...:D...As a matter of coincidence this Pi-square graph contains exactly those reasons with more or less weight factor which I would have said after becoming a professor. (Click the image to get a larger view)

FERMI(GLAST) versus LQG-ists...

It was being speculated for a long time since the launch of FERMI (http://fermi.gsfc.nasa.gov/) that Lorentz Invariance Violation (LIV) which is an integral part of Loop Quantum Gravity(LQG) would be tested by FERMI data. I have never studied LQG. After going through first two three pages of Carlo Rovelli's book I had given up. Thus I have no idea how LIV comes out of such theories. Finally as it was expected, FERMI has got some data which apparently make LQG inconsistent. This is what a recent paper by FERMI collaboration titled "Testing Einstein’s special relativity with Fermi’s short hard γ-ray burst GRB090510" says. According to LQG photon speed v_ph is a function of its energy E_ph and can be very different from its low energy limit v_ph = c (E_ph -> 0) at enegies of the order fo Planck mass M_pl or say M_qg. Thus taking high energy photon data from Gamma Ray Bursts (GRB) and then noting down the variation of v_ph from c a lower limit can be set on M_qg. According to this latest paper FERMI data gives rise to the following limit M_qg/M_pl > 120 which contradictory to most quantum gravity scenarios where M_qg <~ M_pl. And it hardly makes any sense to talk about physics at an energy scale beyond Planck scale since at this scale gravity becomes so strong that everything collapses under gravity giving rise to a singularity. However these FERMI predictions may turn out to be wrong which would be a good news for LQG-ists obviously but as of now it seems they are in real trouble....;)

N=8 SUGRA versus String Theory...

I was attending SERC(Science and Engineering Research Council) THEP (Theoretical High Energy Physics) Main school in IIT Guwahati from 2nd -21st March 2009. It was during a string theory tutorial when I asked this question to the tutor Nemani Suryanarayana (IMSc, Chennai). My doubt was like we remove the quadratic divergences in scalar field (Higgs) theory by introducing supersymmetry, is the same technique can prove useful in removing or controlling the divergences in the S-matrix theory of gravitation. Since getting a renormalizable (finite) theory of gravity is one of the main motivation to do string theory, I was wondering if that could be done with usual quantum field theory with supersymmetry. Prof Nemani told me that N=8 Supergravity (local supersymmetry) in four dimension may give rise to a finite theory of gravity, but nobody has proved it beyond two loops so far. Today however I have seen a paper which was put in ArXiv sometime in May(http://arxiv.org/abs/0905.2326) which discusses this issue upto four loop calculation. Although this is a good improvement over earlier results yet someone has to prove it for the most general order. Then only a finite quantum theory of gravity with N=8 local supersymmetry will be possible. Its difficult for me to comment on string theory since I hardly know much about it. Even if N=8 SUGRA comes out as a finite theory of gravity in four dimension that won't rule out or do any harm to string theory. They are not mutually exclusive, rather one converges to another asymptotically. It is also to be noted that N=8 SUSY is unrealistic, our world has N=1 SUSY (if any) and N=1 SUSY is not enough to remove the divergences which appear in quantizing gravity. Thus although a finite N=8 SUGRA in four dimensions will be a good news yet that's not the end of story.

Another Independence Day...

Today its the 63 rd Independence day of my country. India became a free nation from the British colonialism on this day in 1947. It's been such a long time till today, but I am yet confused about the meaning of independence. It hardly makes any difference to me. I have grown up in this country with a perception that 15th August is a holiday. Not just an ordinary holiday, but a special one when it's not only that people don't go to office and schools but all the shops, markets as well as vehicles on roads come to standstill. That may sound too weired to my fellow Indians, but that's what the scene I have witnessed in North-East India. Most of the extremist groups there who are fighting ( or spreading terrorism ?) for the so called sovereignty call for boycotting events like Independence day, Republic day etc. They don't even bother to blow a group of kids celebrating Independence day in their school. I still remember I used to play cricket with my friends on the national highway. You can just imagine how deserted the public life there is on this day. It's been more than 6-7 years of my stay outside Assam as well as North-East, I don't know what people's perspectives are nowadays about Independence day. May be people nowadays dare to come out of their homes to celebrate I-day. But for me the reminiscence of I-day during my childhood days still make this very special day for Indians just a holiday. Anyway I wish the people of our beloved country India, the largest democracy in the world a very happy Independence Day. Jai Hind.

Trekking trip to Rajmachi...08-09 August'2009

It was the best as well as the longest trekking experience in my life...the trip to Rajmachi fort was simply awesome and will always be as fresh as it is today. We were six people altogether from IIT Bombay. I always prefer to go in a group of less than ten people and six was perfect for me. The trip was fun from the very start..we had to walk almost four kilometres from our hostel to Kanjurmarg Railway station to catch the 0455 hrs local train to Karjat. We walked like anything to reach the station just in time. I wanted to sleep in the train itself since I took a very small nap that night, but that didn't happen. The beautiful landscape on the way to Karjat did not let me sleep at all. We reached Karjat at around 6:30 AM. Then we took auto rickshaw to reach the place which was at the bottom of a hill, in fact that was the place where we started our trekking. The way to Rajmachi from Karjat is not like a normal road..it was just a narrow strip which sometimes become invisible and you may feel like going nowhere. But that's where the fun part of trekking is ;)

We kept going up and up..got lost also in two three places, found a dog as our guide for some part of the journey, got some hints from two-three local people whom we met on the way. Finally at around 11:30 AM we reached the village which is around 100 metre below the fort. We were so tired that we decided to stay there overnight. Since there were no hotels there we approached a family in that village if it would be possible for them to give us a room and food for one night. Fortunately we got a "yes" from them. After taking a little rest and some food we started the second phase of our trek to the forts. There we found lots of other people who had come through the way from Lonavla which is like a proper road. The forts namely Manoranjan and Shree Vardhan were truly amazing. It's hard to believe that people built such huge forts in early days at such a location. We came back from the fort just before nightfall to the house. There was no electriity in that village, they have a solar power system but that operates only in sunny weather. We had nothing to do other than having dinner and then sleeping.

We got up very early in the morning next day since we had to cover the longer route to return from the village. We took the way to Lonavla from the village which was a very easy one with little fun. But the view was superb with lots of waterfalls, rivers in between. We took a bath in one of the rivers, it was really amazing. I never took a bath like that in a river and that too inside a forest, with hills in the surroundings. We kept moving on the way to Lonavla with another dog this time as our guide :D. We reached Lonavla around 1 PM. We were very hungry as well as tired, had lunch there and then took a train back to Bombay. Lonavla was a little scary as we could see lots of people wearing masks ( as a preventive of swine flu). Finally we reached the institute at around 6 PM. I was not being able to make any movement after that..Although it was damn tiring (My muscles are still paining a lot..:( ..) yet the memories will remain evergreen...:)

Weinberg's three QFT volumes have Indian print available now...:):D

Just came to know about this pretty cool news. The Indian edition of Quantum Theory of Fields Vol I, II and III by Steven Weinberg are now available in the market. However they are not as cheap as you might have expected like Pearson, John Wiley books. These books are hardcover and come with a stupid rule that you need to buy all the three volumes at a time. That's what the bookshop people told me. I am not sure if this rule is made by the publishers. Anyway I have started saving money to buy these volumes. The three volumes cost around four thousand rupees. Hope to purchase them by next month.

প্ৰণৱ কুমাৰ বৰ্মনৰ এটি কবিতা

সন্দিকৈ কলেজৰ তুমি সাগৰিকা বৰদলৈ
তুমি সাগৰিকা বৰদলৈ কুশলে আছাতো ?
তোমাৰ বাবেই মোৰ শব্দৰ গুহাত গজি উঠে হুমুনিয়াহ
পাণ বজাৰলৈ নাজাবা সন্ধিয়া,
সান্ধ্য আইনেৰে মাতাল দিঘলী পুখুৰীৰ পাৰ
অশ্লীল হৈ পৰিব পাৰে তৰাবোৰ
কিমান অশান্ত বতাহ নিশান্তৰ কামনা
সাগৰিকা, তুমিতো জানাই মই প্ৰেমিক চৰাই
তোমাৰ অভিমানৰ পুখুৰী সিঁচি লৈ আহিম ড'ৰিকণা
মোৰ একোৱাৰিয়ামত নাচিবলৈ
মই ড'ৰিকণা ধৰিবলৈ বৰশী নাবাও
তোমাৰ দুখৰ পোছাক ধুবলৈ মই ধোবাও
তুমি কি ভাল পোৱা গৰমত? চিত্ৰা, মিৰিন্দা নে থামচাপ ?
আমেৰিকা আমাৰ বাবে ঘৃণণীয় শব্দ
ঘোলা পানীত কলেৰা খাই যৌবনপ্ৰাপ্ত মোৰ দেশৰ অযুত শৈশৱ
তুমি কি ভাল পোৱা? মেড'না নে মাইকেল জেকচন
মোক বধিৰ কৰি পেলোৱা সাগৰিকা

Finally found an awesome course.....

After almost two weeks of confusions which course will be available for us or not, its finally sure that the course we were looking for on Quantum Optics by Prof B.N.Jagatap (Homi Bhabha National Institute) is going to be started next week. There are a total of nine students so far registered for this course. Today the prof has sent a file containing the course contents. Quite contrary to our expectations, the course contents are not so boring, in fact they are really worth learning. The file he has sent contains the following:

Objective: To provide an understanding of the quantum nature of light and to teach how quantum optics serves as a test bed for the foundations of quantum mechanics

Pre-requisite: Course in advanced quantum mechanics

Contents:

Quantum theory of light: field quantization, lamb shift, quantum beats

Quantum theory of coherence: Photon detection and quantum coherence functions first order coherence and Young’s double source experiment, second order coherence, Physics behind Hanburry-Brown and Twiss experiment, interference of two photons, photon antibunching, Poissonian and sub-Poissonian light, photon counting and photon statistics

Classical and nonclassical light: coherent, Fock and squeezed states of light, coherent state as an eigen state of annihilation operator and as a displaced harmonic oscillator state, properties of coherent state, Physics of squeezed states, squeezed state and uncertainty relation, squeezed coherent state, quadrature variance, multimode squeezing, squeezing via nonlinear optical processes, applications of squeezed states for quantum noise reduction beyond standard shot noise limit

EPR paradox, hidden variables, Bell’s theorem and quantum cryptography

Quantum nondemolition (QND) measurement: conditions for QND, QND measurement of photon number by optical Kerr effect and by dispersive atom- field coupling, QND measurement in optical parametric processes

Quantum optical tests of complimentarity: A micro maser which path detector, quantum eraser and quantum optical Ramsey fringes.

We were worried about the course thinking that the instructor may go on teaching stuffs like LASER etc which we had already done last year. But it appears to be quite opposite. The foundation of quantum mechanics is one of the toughest problems yet to be solved completely and lots of research works are still going on. So hopefully this course will give us a good feeling of that field of which we never got any exposure.