Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Theory of electron-phonon superconductivity: Does retardation really
  lead to a small Coulomb pseudopotential?   The theory of electron-phonon superconductivity depends on retardation
drastically reducing effects of the strong Coulomb repulsion. The standard
theory only treats the lowest order diagram, which is an uncontrolled
approximation. We study retardation in the Hubbard-Holstein model in a
controlled way using perturbation theory and dynamical mean-field theory. We
calculate analytically second order results for the pseudopotential $\mu^*$ and
demonstrate the validity up to intermediate couplings by comparison with
non-perturbative results. Retardation effects are still operative, but less
efficient, leading to somewhat larger values of $\mu^*$. Therefore, our theory
can help to understand situations where the standard theory yields
overestimates for $T_c$.

10
The categories of this paper are: q-bio
18
The categories of this paper are: econ
21
The categories of this paper are: adap-org
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
24
The categories of this paper are: dg-ga
22
The categories of this paper are: chao-dyn
5
The categories of this paper are: gr-qc
30
The categories of this paper are: q-alg
2
The categories of this paper are: math
8
The categories of this paper are: hep-ex
3
The categories of this paper are: physics
29
The categories of this paper are: funct-an
31
The categories of this paper are: ao-sci
12
The categories of this paper are: nucl-th