Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Understanding the gravitational-wave Hellings and Downs curve for pulsar
  timing arrays in terms of sound and electromagnetic waves   Searches for stochastic gravitational-wave backgrounds using pulsar timing
arrays look for correlations in the timing residuals induced by the background
across the pulsars in the array. The correlation signature of an isotropic,
unpolarized gravitational-wave background predicted by general relativity
follows the so-called Hellings and Downs curve, which is a relatively simple
function of the angle between a pair of Earth-pulsar baselines. In this paper,
we give a pedagogical discussion of the Hellings and Downs curve for pulsar
timing arrays, considering simpler analogous scenarios involving sound and
electromagnetic waves. We calculate Hellings-and-Downs-type functions for these
two scenarios and develop a framework suitable for doing more general
correlation calculations.

16
The categories of this paper are: stat
11
The categories of this paper are: hep-lat
25
The categories of this paper are: patt-sol
23
The categories of this paper are: solv-int
15
The categories of this paper are: nucl-ex
12
The categories of this paper are: nucl-th
27
The categories of this paper are: comp-gas
31
The categories of this paper are: ao-sci
6
The categories of this paper are: astro-ph
10
The categories of this paper are: q-bio
34
The categories of this paper are: chem-ph
26
The categories of this paper are: bayes-an
18
The categories of this paper are: econ
13
The categories of this paper are: quant-ph
0
The categories of this paper are: hep-ph
29
The categories of this paper are: funct-an