## Friday, November 26, 2010

### Delhi proved it once again!

Commonwealth games brought a vast difference to the capital city of India in terms of infrastructure, road, transport, quality of living etc. The successful completion of the games put a very good impression of the city at international level. But better roads, better way of transport do not always mean that the people are good and Delhi has proved it once again. Delhi has maintained the top position in the country probably for a long time in terms of crime against women. It is considered to be one of the most unsafe city for women in India. That clearly shows the typical mind-sent of common people towards women there. The day before yesterday there was another incident of gang-rape in the city. And this time also the victim was a BPO employee. No wonder that states like Haryana which is the worst sufferer of problems like female foeticide, honor killings, dowry and all neighbors the capital city. Until the people change their mindset, develop a little respect for women I doubt if such incidents can be stopped by strict law and order. Delhi has a mixed crowd, people from various parts of the country come there for various purposes. Out of them, may be the number of people coming from the seven north eastern states is the largest. And the crime against north eastern women is also largest. Apart from the most heinous act of rape, there are many incidents of racial abuse also. And north eastern people who look different from the people of rest of India fall prey to such racism very easily. People call them "Chinki", a disgusting word which I came to know of when I went to Delhi for the first time to pursue my BSc. When I introduced myself to couple of friends in the college and told them that I am from North East, their first reaction was how come I don't look like a chinki. People are so used to these words that they don't even think this could be a racist word. You can't make fun of people with their looks, color etc. But it's hard to convince people. Most of the time I give up when I try to convince anyone that these words make fun of people's look and we should not use them. But the same people reacted like anything when there was racial attack against Indians in various cities in Australia. Racism of any kind and anywhere is intolerable and I regret to say that Indians also suffer from it in their country. But it always goes out of notice to most of us, people think the abusive words are just for making fun. They are not only abusing the north eastern women, but at the same time they are making them look like alien to the rest of the people in the city. They feel lonely, insecure because of this and the most unfortunate ones become victims of the most heinous act of rape followed by murder sometimes. We can't always keep blaming the law and order situation, government, police for failing to provide safety to the women in a city. We, the people have to change and develop mutual respect towards our fellow human first.

## Sunday, November 21, 2010

### CDM vs WDM

I have been a fan of CDM(Cold Dark Matter) since I learned about dark matter and and it's particle interpretation. By "Cold" it simply means non-relativistic at very early stage of the Universe ( = when it decoupled from the thermal equilibrium and got frozen whereas other standard model particles were still in equilibrium). Their mass can vary from a few GeV to TeV. People who love supersymmetry, would always bet for CDM since supersymmetric models naturally provide a CDM candidate without any ad-hoc assumptions. R-parity, a discrete symmetry which is ad-hoc in Minimal Supersymmetric Standard Model (MSSM), but naturally arises in gauge theories where B-L is a part of the gauge symmetry (Left-Right Symmetric Models for example) makes the CDM perfectly stable. Thus it can satisfy both cosmological relic density constraints as well as structure formation bounds.

Although CDM has been taken most seriously among other Dark Matter interpretations in the last 2-3 decades, there is no experimental evidence yet which can confirm CDM over others. And this slightly discouraging fact demands us to be a little open minded. I recently read a paper by Manfred Lindner et al (Physical Review D 2010) where they have talked about Warm Dark Matter in Left-Right Models (LRSM). Warm means slightly lighter than CDM (mass of the order of say keV) and hence they could be relativistic for a long time. And the most natural candidate is sterile neutrino which naturally arise in LRSM as a part of the Right handed doublet. But since, they are considering non-SUSY models, the stability of sterile neutrino is not guaranteed and hence they have to fit the parameters in such a way that the life-time of the lightest sterile neutrino exceeds the age of the Universe. Although this does not look elegant like in SUSY models, but this is a good alternative and it does not cost you too much. You have far less free parameters compared to SUSY models and it will be easier to rule out or confirm such models in the experiments. In this paper, the authors are focusing more on how the keV scale sterile neutrino DM can satisfy the cosmological bounds as well as neutrino oscillation data. And they have shown it does, although with some undesirable features like one active neutrino becomes too light ( 9 orders of magnitude smaller than 1 eV, but still allowed from neutrino oscillation data).

Apart from cosmological and neutrino oscillation bounds which are of course the most crucial test for a dark matter candidate, there should be a way to actually observe it. The ongoing direct detection experimental results, I don't think we can fit with a keV sterile neutrino. The indirect detection experiments like Positron excess will be even harder to fit with such WDM candidate. But in any case these indirect detection experimental results have other astrophysical explanations and the various direct detection experiments don't agree with each other. Even if LHC gives clue about such keV sterile neutrino, we still wont be able to say if it is the true dark matter candidate or not. We still have to rely on direct detection experiments, provided all of them agree with each other. Anyway as G. Bertone commented in one of his recent review (to be published in Nature), we can not keep on proposing more and more experiments to search for dark matter endlessly, if we do not get some positive signal in coming few years, may be there is a need of paradigm shift and we need to look for alternative scenarios. The worst such alternative to me would the MOND theories. They look so ugly to me that I wont ever be able to believe Nature surrendered herself to them!

## Thursday, November 18, 2010

### DAE Symposium 13-18th Dec'2010, Jaipur

Finally my trip to Jaipur next month is finalized. The abstract I submitted got accepted for an oral presentation. I will be presenting my paper with the PRL guys on D-parity breaking and TeV scale left-right symmetry (http://compactified.blogspot.com/2010/06/arxiv-number-2.html ) . This is going to be the first conference where I will be giving an oral presentation. I am a little scared but I already have enough of such presentations in IITB, so won't be a big deal I guess. Apart from the main results of the paper, I might include some other stuff also which could be a mere proposal at this stage since I have not completed those studies in details. I am looking forward to meeting couple of old friends as well as some well-known people in HEP from all over India. Apart from that Jaipur is one of the hottest (not in terms of temperature :P) tourist destinations in India and most importantly I have never been there except the train station through which my train passed through on the way to Delhi many times. If time permits I am planning to go to Ranthambore, Bharatpur also. These are very famous for wildlife (specially tigers and migratory birds). December will be very tight it seems as I am also planning to come to PRL, Ahmedabad after the conference for some work. I am not at all sure about new years eve party this time. I might not be able to celebrate it in Delhi like in last couple of years. Hope it happens once again. Keeping my fingers crossed right now.

## Friday, November 12, 2010

### Jai Ho Part II

India is great indeed. Recently you might have heard about the resignation of Maharashtra Chief minister Ashok Chavan amidst the controversies of his involvement in multi-crore Adarsh society housing scandals. Apparently the Maharashtra government allotted the land to the builders without proper approval from environmental ministry and beyond that, the flats which were meant for the family members of Kargil war heroes, the politicians and few corrupted defense top people shared among themselves. This became such a huge issue that the ruling party had to sack the chief minister and replace him with his successor Prithviraj Chavan. This is one story which is quite acceptable. But the same Congress government which sacked Maharashtra Chief minister is now defending another minister who is involved in so called 2G spectrum scam. The Adarsh society scam might have involved maximum of thousand crores, but this 2G scam involves an unbelievably huge 1.7 Lac Crores. Yes, I am talking about telecom minister A Raja. In terms of the public money involved in this scam, if Ashok Chavan deserved resignation, this guy should deserve public execution. I don't know where are those people now, who were shouting against the Commonwealth Games (CWG) saying the money (around 78 thousand crores if I am not mistaken) spent on the games could have been used for the cause of poor people. Although CWG was also hit by multi crore corruption, it was not as bad as this 2G scam. At least success of CWG could build a better image of India in the global stage. There should be huge public rage against such corrupted politicians like A Raja, and they should not just be sacked down from the current post, but should be given severe punishment.

The second part of Jai Ho is regarding construction of dams. India is very well known for throwing poor people out of their lands without giving enough compensation to construct dams. Narmada Bachao Andolan led by social activists Medha Patkar is one of the best example. Constructing dams, highways is no offense, provided the poor people who sacrifice their lands are given good enough compensation. In a country where one politician can lead a scam of 1 lac crores is it a big deal? Certainly not. India is currently building around 100 dams in the state of Arunachal Pradesh. The river Brahmaputra as well as most of its tributaries which flow across Arunachal come down to Assam, the neighboring state. And, you can imagine how these dams are going to change the eco-system in the entire state of Assam. The Government is saying dams are needed to control floods whereas people who have done study on it are saying the height of the dams are above the danger limit and if these dams start operating, it will bring terrible danger to the state of Assam. There is a huge public agitation going on across the state of Assam nowadays but it seems the state as well as the central government are completely indifferent to the concerns of the people of Assam. There was a committee composed of Professors from IIT Guwahati and Gauhati University to study the impact of dams in Arunachal on neighboring states like Assam. They gave a green signal to the dams based on their incomplete study, but according to Prof Shivaji Rao, the heights of the dams are still questionable http://www.downtoearth.org.in/node/1978 . There was also a news that the government gave a bribe of around 30 lacs to the professors in the report committee to give a green signal to the dams. Today I have seen another terrible news that now the central government is proposing 10 huge dams in the neighboring country Bhutan completely ignoring the outcomes of such dams in hill states on the plain regions of neighboring state Assam. This same government which is designing blue-print to destroy one state by constructing dams in another state, makes too much hue and cry when China attempts to build dams in Tibet on the river Brahmaputra as well as other small rivers which flow down to North East India. This does not make any sense at all to me. No matter who builds the dams, equal number of Indians will be affected by them. Anyway the way things happen in this country is beyond my imagination all the time. Jai Ho once again!

## Tuesday, November 9, 2010

### Maiden Trip to South India

I had my maiden trip to South India this weekend. The diwali vacation along with the weekend put me on an advantage to make such a trip. I went to the city of Bangalore, the capital of the Indian state Karnataka. I am sorry that I would stick to the older name of this city in my post, as changing names of cities don't make any sense to me at all. The new name of this city is perhaps Bengaluru if I am not wrong. Anyway, the trip to Bangalore from Bombay is 24 hour journey by train. The journey was very pleasant as the weather was cool all through. The train route was like a train route to a Hill station. There was no electric lines, the train had a diesel engine and it passed through forests, mountains etc. I really felt as if I am going home and not to Bangalore. There were hardly any famous or big stations on the way, the train was mostly passing through rural areas, forests, paddy fields etc. The altitude of most of the stations coming on the way were more than 500 meter from sea level and may be the that's the reason why the weather was pretty cool throughout. Even if there is rainfall, people don't feel the humidity. It was a different experience from Bombay, where rain means too much humidity and you sweat like hell.
The city of Bangalore was really nice, I found it quite clean and systematic compared to Bombay. I missed the Bombay local train there. The only mode of public transport was bus there. Although I did not have to take any bus, I could guess how difficult it would have been for me if I had to. The sign-boards in the shops, restaurants, buses were mostly in local language, neither in Hindi nor in English. I could just imagine how hard it would be for a new-comer to get adjust to the city life. I found it a bit weird, at least English should be used in the public notice boards if not Hindi. I did not have much time to explore the city, but these were my first sight experiences. I would love to go there once again, may be in March next year. This time I am thinking of visiting IISc for a week or so, so that getting leave from IITB will no longer be an issue. And at the same time will get an opportunity to explore Bangalore and its neighborhood (Mysore for example).

## Monday, November 1, 2010

### 1010.6289

Even after losing enthusiasm after going through tedious peer review process, I finished the latest work (and first with my supervisor :P) and it has come on arXiv.org today with the reference number in the title of this post. It is about gauge coupling unification, fermion mass universality and type I seesaw dominance in supersymmetric left-right models with natural conservation of R-parity. The abelian B-L gauge symmetry is broken by Higgs triplet fields with B-L charge 2 and hence R-parity defined as
$R_p = (-1)^{3(B-L)+2S}$
is conserved. The good thing about this is the natural presence of stable cold dark matter candidate in the model in terms of the lightest supersymmetric particle (LSP). Anyway our focus is not on this issue. We have found that at the cost of adding a few extra superfields, the minimal version of such models give rise to gauge coupling unification (at very high scale in agreement with proton decay constraints) as well fermion mass unification. The fermion mass unification relations in SO(10) grand unified model are
$m_b = m_{\tau}, 3m_s = m_{\mu}, m_d = 3m_e$
What we find is that fermion mass unification is achieved properly only in the case of third (and hence the heaviest) family of fermions whereas there is some discrepancy in the case of lighter fermions. However such issues can be handled with proper threshold corrections which can be found in the literature. Good thing is that such good characteristics of gauge coupling unification and fermion mass universality can be achieved in a left-right model only which is tremendously simpler than a GUT model like SO(10). But of course SO(10) has its own charm and can't be ignored. The point is that, the desert below the GUT symmetry breaking scale at very high scale is ruled by the effective supersymmetric left right model with some additional light superfields which are part of the SO(10) gauge structure but remained light somehow till the TeV scale (for example). Our approach was bottom up in this case, however it will be good to realize this in a top-down approach. That's the goal of next project.