Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Fermi's golden rule and exponential decay as a RG fixed point   We discuss the decay of unstable states into a quasicontinuum using models of
the effective Hamiltonian type. The goal is to show that exponential decay and
the golden rule are exact in a suitable scaling limit, and that there is an
associated renormalization group (RG) with these properties as a fixed point.
The method is inspired by a limit theorem for infinitely divisible
distributions in probability theory, where there is a RG with a Cauchy
distribution, i.e. a Lorentz line shape, as a fixed point. Our method of
solving for the spectrum is well known; it does not involve a perturbation
expansion in the interaction, and needs no assumption of a weak interaction. We
use random matrices for the interaction, and show that the ensemble
fluctuations vanish in the scaling limit. Thus the limit is the same for every
model in the ensemble with probability one.

30
The categories of this paper are: q-alg
37
The categories of this paper are: supr-con
35
The categories of this paper are: mtrl-th
9
The categories of this paper are: nlin
31
The categories of this paper are: ao-sci
22
The categories of this paper are: chao-dyn
26
The categories of this paper are: bayes-an
7
The categories of this paper are: hep-th
8
The categories of this paper are: hep-ex
32
The categories of this paper are: atom-ph
17
The categories of this paper are: q-fin
19
The categories of this paper are: eess
0
The categories of this paper are: hep-ph
36
The categories of this paper are: cmp-lg
11
The categories of this paper are: hep-lat
23
The categories of this paper are: solv-int