# HEP/Astro Seminar, Wednesday 24 September 1997

## Jens Andersen (The Ohio State University)




### Abstract

In this talk I will discuss the effective field theory approach to finite
temperature field theory. The basic idea is that in the imaginary time
formalism there is a summation over Matsubara frequencies in loop diagrams.
These frequencies which are $2\pi nT$ for bosons and $(2n+1)\pi T$ for
fermions act as (tree level) masses in the propagators. The Appelquist-
Carrazone theorem then suggests that the nonzero bosonic modes as well as
the fermionic modes decouple at long distances. One can then construct an
effective three-dimensional field theory which is valid at long distances
and which can be used in calculating physical quantities. I illustrate
these ideas and methods by calculating the screening mass in
$g^2\Phi^4$-theory.


## 3:30pm, Smith Lab 4079

Francesco Antonuccio ( anton@pacific.mps.ohio-state.edu), last updated 22-SEP-97.