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Archive for April, 2011

Here is an announcement of a program I will be organizing at the KITP from Jan 17 thru March 9 2012. It is a program on numerical methods for gravity and QFT. The web page of the program is located here.

Here is the image I made to illustrate the program: it is generated by taking a set of modes in a box with a UV cutoff. Then amplitudes are seeded for these modes with random numbers and phases multiplied by the typical quantum uncertainty on each mode. The result is a picture like the one below.

It is also fun to animate it.

Right now I have to start chasing people and reminding them that the (first) deadline for applications is coming soon (April 30th).

In the meantime stay tuned.

Image of Fluctuations of quantum fields

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If you don’t know this, Xenon 100 released their most recent limits on dark matter. This was covered in the New York Times, and also by Sean. The data can be found in this paper in the arxiv: “Dark Matter Results from 100 Live Days of XENON100 Data“.

The main key of these experiments is to keep some region where data is supposed to be located at completely hidden from the experimentalists until they have decided how to account for all the systematics with the control region. Once they do this, they unblind the data and hope that enough events are in the discovery region to have a discovery. These regions also can have some events that are due to other sources which the experimenters have tried as hard as possible to remove. The data was unblinded about a week ago, and everything was essentially ready for writing a paper. This last step is very fast, because there are very few events expected anyhow.

Previous to the end announcement: that no dark mater was found yet in the Xenon direct experiment, I had been hearing rumors all week long that Xenon 100 had actually seen something.

Well, you can call this the sociology of the field: some people might have been expecting something and claimed that it was in the data. Otherwise its a publicity stunt. There are two experiments with claims of detection: DAMA/LIBRA and COGENT. Many people are very suspicious of the first, and a lot of them should be also worried about the second. With the new data it seems as if both positives are ruled out unless one has a very contrived model of dark matter.

 

 

 

 

 

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Quantum tunneling

This week I have been explaining quantum tunneling in quantum mechanics and quantum field theory for my class. It is a fun subject and when I was educated in it a few details were left out. Happily nowadays its easier to find that information. I’m particularly happy with the description of this set of phenomena in the book by Tom Banks: “Modern Quantum Field Theory” , where he actually goes very carefully about how instantons and such are related to the WKB approximation in quantum mechanics, so that one has a rather strong intuitive sense of how these ideas interpolate between the abstract Euclidean formulation of the path integral and a phenomenon that we can understand in other ways.

 

The rest of this article is a rant on technical details without equations. Now that I have advertised where I’m getting my information from, I could stop here. However…

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