Thursday, May 26, 2011


The title of this post refers to the pre-print of my paper which appeared in today. It's about domain wall formation in spontaneous R-parity breaking models and one possible way to get rid of them by introducing gravity induced higher dimensional operators. Before I go one step further may be I should say something about various technical terms appearing in the last sentence. Domain walls are two dimensional objects which are formed whenever a discrete symmetry gets spontaneously broken. They have a finite topological charge and hence are stable. In our work, this discrete symmetry is the left-right symmetry under which the left handed chiral fields are exchanged with right handed chiral fields and vice versa. Left(right) handed means direction of spin is opposite(same) to (as) the direction of momentum. This discrete symmetry arises in one very promising extension of standard model of particle physics where tiny neutrino masses naturally arise by seesaw mechanism. These domain walls are extended objects and hence will start dominating the Universe after the matter and radiation energy density decreases below a certain limit. However this is against observation, as we know our Universe is mostly matter dominated (+ a cosmological constant) from WMAP and other related experiments. Thus there needs to be some mechanism to make these walls disappear. One possible idea is to create a small pressure difference between two sides of the wall so that the true vacuum expands to occupy the entire causal Universe. We have talked about gravity induced higher dimensional terms (> dimension 4) which break the discrete symmetry explicitly creating the required pressure difference. How these higher dimensional terms break parity is a part of some higher theory (may be hidden sector supersymmetry breaking models, or some quantum gravity models) and we do not discuss that further in our paper. The domain wall disappearance through this mechanism however puts strict constraints on the discrete symmetry breaking scale. In one class of models (having Higgs triplets and hence type II seesaw), this symmetry breaking scale has to be pretty low (< 10^5 - 10^7 GeV) . But if this theory is a part of some higher theory such as SO(10) grand unified theory, then this left-right symmetry breaking scale has to be pretty high and hence is in disagreement with the constraints coming from domain wall removal. We also discuss another class of models (with Higgs doublets and hence type III or inverse seesaw) where both these constraints can be satisfied simultaneously. The good thing about models with Higgs doublets is that domain wall removal does not put very strict constraints on the symmetry breaking scales and hence do not give rise to conflict with grand unification which usually forces the symmetry breaking scale to be very high. Comments and criticism are welcome :)

Saturday, May 21, 2011

Adios Shane Warne..we will miss you!

Yesterday the iconic leg spinner Shane Warne had his last match of his life and I was quite fortunate to watch it live at Wankhede Stadium, Mumbai. It was an Indian Premiere League (IPL) match between Rajasthan Royals and Mumbai Indians. It was the first time for me to watch a match live in a stadium. And it was a damn good experience. Wankhede is a beautiful stadium specially under floodlights. The cool breeze from the Arabian sea keep passing through the stadium all the time. And it also changed my earlier perception that people hardly can recognize any player on the ground, I could actually locate each and every player on the ground and it was really fantastic. Regarding cricket, the match was totally one-sided with Rajasthan Royals winning by 10 wicket giving their captain Warne a perfect farewell. The crowd was pretty cool as well. Although Mumbai Indians were losing the match in front of their home supporters, yet the crowd was not taking any side much. They were cheering for Rajasthan Royals players like Watson, Dravid as well. An awesome stadium, a superb crowd and a couple of perfect cricketers in the match will make my first ever experience in a stadium memorable forever :)

Wednesday, May 18, 2011

A new course, a new institute: No big deal?

New institutes, new Universities are coming up in many places across India. Although the need of such new institutes in a country with second largest population in the world can not be ruled out, the question often asked is whether the new institutions are living up to the expectations of the students, their parents or other fellow countrymen. Of course the academic reputation of an institute can not be purchased or built instantaneously and it takes some time, the government should at least make sure some of the minimum requirements before opening new institutes or universities. The same is true when an institute introduces a new course. The government often hurries a lot in the process it seems, may be because of the coming elections or some other sacred reasons which I can't think of. Couple of new IIT's were introduced four years back, and most of them without proper infra-structure. Most of them did not even have their own campus, the respective state governments were yet to allot land for the campus. So the new IIT's were either operating from some state government engineering college campus (like refugees) or in extreme cases operating from a different state within the campus of its mentor IIT. The students who might have got a place in a good NIT with good infra-structure and reputation opted for several such new IIT's thinking that the brand name will work. Is that enough? People don't come to IIT just for the tag. The life in IIT has more than just a tag. After spending five years in a premier institute like IIT Bombay, I know how much valuable the life here is, and at the same time I feel sad to see the new IIT's not yet having their own campus. The first 3-4 batches of these IIT's won't even see their own campus. Apart from that, the government also increased the intake of students in the IIT's introducing reservations. Even the older IIT's have become too much populated now, with many hostels are being under construction, reducing the green coverage as well. I can imagine how crowded the new IIT's will be which are operating from other colleges by occupying a small portion of the campus. It would have been much better if these IIT's were started at least after the land for the campus were allotted and are in a position to operate from their own campus.

Similar is true when an institute introduces a new course. They often overlook the fact that the infrastructure in the institute might not support that new course as well as the new students who will opt for the course. For example, the MSc-PhD dual degree course introduced in IITB in 2005 still sounds like alien to many of the academic office people. They have not yet mentioned this course in various certificates and we need to write our course name by hand there. They do not even know that after finishing MSc coursework we should get as much fellowship as other regular PhD students get. They are also confused whether they should give PhD, MSc or both the degrees after we complete the course. In short they are yet to introduce a proper booklet mentioning the rules and regulations about this new course. They just introduced the course six years back without giving much thought about it. One more problem this course facing is the availability of PhD supervisors. The institute takes regular PhD students twice a year, and every year one batch of Dual Degree with seven students are getting added to the list. So around 15-20 people are getting admitted to a course in the department which will ultimately lead to PhD degree. But do the department has as much infrastructure or faculty for that? Nobody seems to have an answer. Earlier the students had lots of freedom in choosing their topic as well as guide, but that no longer seems to be there since many faculty members have stopped offering projects due to overload. The institute should think about all these issues before taking new students every year. Hope to see some changes soon!

Tuesday, May 17, 2011

Boring Summer!

This summer seems really boring with no plans to go to some school or conferences. I don't remember when I spent the whole summer in the institute in last five years. Either I used to go home or to some other institutes for summer internships or schools, workshops. Although the summer internship option is no longer available, I did not find any conference suitable for me. There were two three of them but of so much high standards that registration limit had crossed limit much before I came to know about them. Most conferences nowadays ask to pay registration fees(a huge sum of money for a grad student in India) before applying which is a big headache nowadays. Although there are some options to get these money reimbursed from various funding agencies in India, the process takes some time. ICTP school is a very good option to look for, but I already attended previous year's Cosmology school. I would have preferred to attend the Particle Physics school this year, but it's impossible to get the funding for two consecutive years, and our institute provides funding only when we go for oral presentation and not for attending schools abroad. Even if I had not applied for the Cosmology school and applied for the Particle Physics school this year, I am not sure if I would have got selected. This time the selection was a bit strange to me since many people with publications did not get selected, may be the organizers are looking for fresh participants who have just joined PhD. It at least gives me the good feeling that I at least attended the Cosmology school last year which was a real good experience. I am looking for the SUSY conference this year in Batavia, Illinois but not sure if will get selected. This is considered to be largest conference for people working in supersymmetry theory and phenomenology. Keeping fingers crossed right now. Anyway, spending the summer in the institute has at least one advantage it seems: the campus is far less crowded and takes me back to my earlier days in 2006 at IIT except one difference in the sense that there are not as many trees in the campus now.

Saturday, May 14, 2011

Another five years of corruption, illegal influx and so on...

Friday, the 13th could not have been worse than this for the people of Assam. While the people of West Bengal were celebrating the much awaited end of CPM (Communist Party of India) rule for 34 consecutive years in the state, the neighboring state Assam has given its fate for next five years in the hands of Indian National Congress (INC) party. It's the third consecutive victory for Tarun Gogoi led INC government in Assam. It is surprising that, although the image of INC has been shattered by the never before corruptions in 2G spectrum, Commonwealth Games scam and many others, although the country woke up to fight against corruption led by Anna Hazare the recent assembly election results did not really hamper INC's image. In Tamil Nadu, although INC ally DMK has lost to AIADMK , it's not very surprising there. Such shift from one party to the another is very common there after a gap of 5-10 years. But the other state's results more or less went in favor of the ruling party at the center, with Assam showing the largest support for INC may be, allowing the party to come into power for 3rd consecutive term.

Inefficient opposition has led to the rise of INC, no doubt. But what sets the alarm in the state this time is that a local party called AIUDF, formed less than a decade ago with mass support from the religious minorities (99% of whom have illegally infiltrated to the state through the Bangladesh border) has become the party with second highest majority. The local mainstream party like AGP, or national party like BJP were completely devastated in this election. Another sad thing is that, no party has gained the minimum number of seats to stand as an opposition in the assembly which means the ruling party won't have any opposition for the next five years, nothing can be more shameful than this in the largest democracy of the world. Although INC and AIUDF had many pre-election differences, the results have shown that both of them are the gainers. Only AGP-BJP are losing the battle. It also raises a doubt whether there were any secret tie up between INC and AIUDF before the election although they never made it public. This has an advantage in the sense that INC will never lose the votes of Assamese people who otherwise won't have supported INC if there was a INC-AIUDF tie up. AGP-BJP did not seem to play any game at all this time, last time at least there was a tie up between them, but this time the division of vote between them cost them a lot. But what AGP might have thought that, if they declared a tie up with BJP, the road to form a coalition government with AIUDF would be closed. So AGP fought their battle alone whereas INC had its declared partner BPF (Bodoland People's Forum), and may be unofficial tie up with AIUDF. And the result is clear, these three parties have got the first three positions in number of seats pushing AGP BJP to 4th and 5th positions respectively.

No matter how INC has won the election, the question now to ask is what can the people of Assam can expect from INC government for the next five years. Obviously INC will continue various schemes it introduced in last few years and common people will enjoy its benefit and will continue supporting INC no matter what the overall development of the state, what the government is doing to stop illegal infiltration from Bangladesh, whether corruption has become low or not and similar issues of broader interest. Yesterday, Chief Minister of Assam Tarun Gogoi said in an interview that the issue of illegal immigration is largely exaggerated which clearly indicates that like in the previous years, the government will keep encouraging illegal immigration for the next five years as well. This is a serious warning, out of the 126 constituencies in Assam, the fate of more than 25 seats are now decided by the immigrants which will definitely increase to 35 or so after five years. We, the mainstream Assamese people will become minorities in our own state within 20 years if the public do not put any effort. May be we need another Assam Agitation to fight for our survival. May God help us, Amen!

Tuesday, May 10, 2011

SUSY..hope you are still there!

Couple of weeks back there were lots of hue and cry among young researchers who might have heard about SUSY but have not worked on it in great details. It's because of the ATLAS and CMS experiment at Large Hadron Collider (LHC), CERN (Geneva) publishing two independent results related to supersymmetry (SUSY) searches in the 7 TeV run of LHC. One of them looked for missing energy+ jet signatures whereas the other looked for lepton+jet signatures, but their conclusion was more or less similar. They ruled out significant amount of parameter space of Constrained Minimal Supersymmetric Standard Model (CMSSM). This is a rather constrained version of MSSM where the number of free parameters are just 5 compared to 124 or so parameters in the MSSM. So obviously the CMSSM has far more predictability and hence getting almost ruled out. Although its really heartbreaking to see such predictable models losing their fight, yet this does not really mean SUSY is not there. We still need more data and scan of other available models to rule out TeV scale SUSY. And even if LHC rule out TeV scale SUSY, it can not say anything about existence of SUSY at even higher energies. But many of the theoretical advantages of SUSY would be lost if we keep pushing SUSY towards higher and higher scales and will be as good as having no SUSY at all. Anyway, hope LHC will soon confirm its presence around the TeV corner. But nevertheless, the ATLAS/CMS result created lots of hype among both experts as well as others. One of our over-curious mate in the department got pumped up so much (may be after reading about it in some newspapers and not in the arxiv papers) that he asked one of our senior prof, what's the point of doing SUSY as LHC has already ruled it out? I don't know what was the professor's reaction at that moment, but I can imagine how shocking such a news (if true) to a person working in particle physics for a long time. Blame it on popular news sites or news papers which put the title of such news in such a way that young kids easily get misled. Anyway, hope many such news (positive I mean) about SUSY would be coming soon from the heart of LHC :)

Sunday, May 1, 2011

Pawan Hans Tragedies and North East!

Just few days back there was a chopper accident in Tawang, Arunachal Pradesh, India (China claims this part as its own land although ;) ) killing around 17 people including 1 or 2 foreigners. There were couple of such incidents before as well. There was a huge demand at that time to suspend the services of Pawan Hans helicopter in North East regions. It was also in the news that the choppers declared as unsuitable for use or outdated, are sent to North East region which are claiming human lives frequently. North East Student Association (NESO) demanded the halt of Pawan Hans service just after this incident last week. But the service of this deadly helicopter was still on. Today the same Pawan Hans helicopter with Arunachal Pradesh Chief Minister on board with four other people has gone missing and the Government now is taking the help of ISRO to locate the chopper. Hope the government will wake up after this incident at least and either suspend the operation of this killer chopper or look into their maintenance.