Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nonperturbative renormalization-group approach preserving the momentum
  dependence of correlation functions   We present an approximation scheme of the nonperturbative renormalization
group that preserves the momentum dependence of correlation functions. This
approximation scheme can be seen as a simple improvement of the local potential
approximation (LPA) where the derivative terms in the effective action are
promoted to arbitrary momentum-dependent functions. As in the LPA the only
field dependence comes from the effective potential, which allows us to solve
the renormalization-group equations at a relatively modest numerical cost (as
compared, e.g., to the Blaizot--Mend\'ez-Galain--Wschebor approximation
scheme). As an application we consider the two-dimensional quantum O($N$) model
at zero temperature. We discuss not only the two-point correlation function but
also higher-order correlation functions such as the scalar susceptibility
(which allows for an investigation of the "Higgs" amplitude mode) and the
conductivity. In particular we show how, using Pad\'e approximants to perform
the analytic continuation $i\omega_n\to\omega+i0^+$ of imaginary frequency
correlation functions $\chi(i\omega_n)$ computed numerically from the
renormalization-group equations, one can obtain spectral functions in the
real-frequency domain.

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The categories of this paper are: hep-ph
22
The categories of this paper are: chao-dyn
15
The categories of this paper are: nucl-ex
36
The categories of this paper are: cmp-lg
17
The categories of this paper are: q-fin
21
The categories of this paper are: adap-org
6
The categories of this paper are: astro-ph
24
The categories of this paper are: dg-ga
25
The categories of this paper are: patt-sol
29
The categories of this paper are: funct-an
8
The categories of this paper are: hep-ex
19
The categories of this paper are: eess
11
The categories of this paper are: hep-lat
9
The categories of this paper are: nlin
16
The categories of this paper are: stat
10
The categories of this paper are: q-bio