Wednesday, July 27, 2005

Lattice 2005, day two

Hello again from Dublin. Day two of Lattice 2005 was the "busy" day,
with three plenary sessions, a parallel session, and the poster
session all in one day. Twelve solid hours of physics, which is
rather tiring, particularly since I was presenting a poster. As such,
today's update of the Plenary sessions will be brief.

The morning started off with a talk by Herbert Neuberger on simulations
of large N field theory. As discovered by 't Hooft, SU(N) gauge
theory simplifies as you take the limit N -> infinity. However, this
is hard to do in Lattice QCD, as you would need infinite sized
matrices. However, there are techniques for attacking the problem.
Neuberger reviewed the interesting phase structure you see in this
system. The lattice version of large N QCD has 6 different phases.

Next up was Simon Catterall, who reviewed his work on Lattice
supersymmetry. In the early days of both supersymmetry and lattice
QCD, it wasn't thought possible to put a supersymetric theory on the
lattice without badly breaking the supersymmetry. However in recent
years, a few different methods have been discovered. The basic idea
is you construct a continuum theory with lots of supersymmetry and
arrange things such that when you put the theory on the lattice, a
remmenant of the supersymmetry remains. Simon reviewed his method for
doing this, and briefly touched on some of the possible applications
of these methods.

After a coffee break, the sessions shifted in focus a little bit.
Chris Dawson reviewed the state of Kaon Phenomenology on the lattice.
The focus here is on kaon decays, which are hard to do in lattice
QCD. For example, a kaon can decay into two pions. This is extremely
hard to compute, since pions are very large, it's hard to fit two of
them inside your finite lattice box.

We swapped last names for the next talk, Chris Dawson became Chris
Michael, who gave a lively review of the state of hadronic decays on
the lattice. The people I work with are interested in doing very high
precision calculations. This is good, however, it limits you to a
small number of thing you can calculate. However lattice QCD can, in
principle, calculate many many more interesting strong interaction
processes. Chris gave an update of the state of some of these
calculations, which are very very hard to do. You have an unstable
particle in the intitial state, two or more hadrons in the final
state, and a transition at some point between. I

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