Friday, April 30, 2010


Supersymmetry is easy, isn't it?. I have posted (in spanish) a brief introduction to the subject. And I'll make more posts abut it. I am almost sure that everyone who has passed a course in QFT can understand the basics of supersymmetry.

After all, you have a superpartner for every particle, that has opposite statistic. You have funny names for the superpartnerts. The partner of the electron is the slectron, the quark has the squark, etc. And for bosonoics fields the thing is easy also. To the photon corresponds the photino, to the gluons the gluino, to the higgs the higssino, etc.

Well, them if you remember that for every broken global symmetry there is an associated particle, the goldstone boson them you know what a goldstino is. Isn't it?

Well, if you read the book that gives title to the entry(the full title is theory and phenomenology of sparticles) you will realize that maybe the goldstino could not be exactly what you think.

And, of course, you will learn a lot more about phenomenology of N=1 supersymmetry in 4 dimensiones. That includes the MSSM, cosmology of supersymmetry models, etc, etc. The books is from 2004 (reprinted in 2007) so it is, I guess, terribly outdated. I find it a lot better option that the,somewhat similar in it's purpose, book of Michel Dine (supersymmetry and superstrings). Ok, this book doesn't cover superstring, and it has many more pages. But with the actual trend of growing interest in phenomenology, motivated by the dark matter experiments, and the beginning of operation of the LHC it looks as a good reference book to get good info about the characteristics of neutralino, methods of supersymmetry breaking or whatever.

P.S. I'll try o update the previous posts, as promised, as soon as possible.

Wednesday, April 28, 2010

Enrique Álvarez on vacuum energy decay

When I studied theoretical physics in the UAM the everybody (well, at least everybody studying he specialty of theoretical physics) favorite teacher was Enrique Álvarez. Possibly, I don't know because I never coincided with him, today Ibañez could discuss the crown, but in that times Ibañez was in CERN and didn't teach.

Particularly great was his course in an asignature devoted to classical mechanics where he explained constrained lagrangian system, and the Dirac way to deal with them. That supposed that I had not any problem in the future understanding quantization of gauge theories, string theories, BRST operators and all that which is a great advantage. Also his course in general relativity was great.

Well, I am happy to see today in arxiv an article of him totally worth to post about:

The article makes comments, and insights, on a previous work of Polchinsky the one of the Polchinsky action)in 2007: (I think he talked about that topic in the strings 2008 conferences celebrated in CERN)

The idea is that in de Sitter space the vacuum is not stable in the presence of interactions among particles. I am still reading both articles so I will not comment on them now, but I will edit this post (yes, I promise xD) as soon as I read them and explain what's going on.

But I am sure that some readers of this blog, who also had Álvarez as a teacher, will not wait me and read the article themselves. After all the requisites for reading are mainly some familiarity with basic QFT and quantization on curved spaces. In fact one of the points of this post is to advise them of the existence of the article and so avoid the possibility that they would miss it.

Friday, April 09, 2010

Á guide for anonymous LHC backholics

A few days ago it was published on arxiv the following paper: Black hole/string ball production, possibly at LHC

I am busy reading any, many things nowadays and I couldn't read it immediately - despite of it's few number of pages - but today, at last, I read it.

The main interest of the papers is that it makes a quick review of the ideas that lead to the proposal of black hole creation on the LHC and to it's characteristics. Most interestingly still, it gives references to the relevant literature.

One of the focus +of the paper is the way on which the Hawking radiation is expected to behave. It is said that the first expectation was that most of the radiation would be send t Kaluza-Klein models of the gaviton that scape to the bulk. In particular a paper stating that was: A Model for High Energy Scattering in Quantum Gravity (note that the article treats other aspects as well).

Later it was argued that instead there would be a lot of hawking emission into brane particles: Black Holes Radiate Mainly on the Brane . In this paper, like in the others, the treatment is semiclassical. No construction of black out of D-branes is used. Neither Hawking radiation is described by string theory objects. Such descriptions exist, to a certain extent, but are not developed enough to use them in this contexts. In fat an analytic description of a black hole in braneworlds is inexistent even in classical gravity and some reasonable approximations have to be made. This approximations are valid for small black holes whose size is much smaller than the length of the extra dimension.

The amount of radiation send to the bulk or to the brane is important. If all the radiation is send to the brane no Hawking radiation would be observed in the LHC.

Well. I think that this article is citing mainly orthodox string theory friendly papers. Be aware that other people argue that a microcanonical statistical ensemble would be necessary. In that assumptions the lifetime of the back holes could be large enough to leave the detectors (but still there woulld, of course, no danger of earth swallowing black holes).

The theme of black hole emission has behind it a lot of publications and many, many, possibilities have been conjectured. One of that is the possibility of formation of a "cromosphere" or an "electrosphere". By that it is understood that the hawking radiation reorganizes into a permanent orbiting matter that obstruct the rest of the outgoing radiation to some extent. A recent paper in arxiv (sorry, I have no time to search the reference now) argues against it.

Also there have been more exotic ideas. For example Louis Crane abrogate for the possibility of creating black holes by collapsing large clouds of dust, of a few tons, by means of implosions. He argues that the resulting black hole would emit in supersymmetric modes and that the radiation could be modulated to use the black hole as a device to impulsate spaceships able to go into other solar systems. I have discussed this, and the one of microcanonical ensembles, possibility in my other blog. You can search there for them (if you speak Spanish).

As the readers could guess some of the suggestions in the literature have more wide acceptation, possible with very good reasons, that others. And, except for the Louis Crane idea, all depends on braneworld sceneries. Recently there was an article in arxiv that gives a wide sight into realizations of that models into full string theory. When I would have read it I'll try to summarize some of the proposals here.

UPDATE: Today Lubos has commented about an article treating black holes: Kerr black hole: the CFT entropy works for all M,J. Of course it is worth reading.