Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The impact of cosmic neutrinos on the gravitational-wave background   We obtain the equation governing the evolution of the cosmological
gravitational-wave background, accounting for the presence of cosmic neutrinos,
up to second order in perturbation theory. In particular, we focus on the epoch
during radiation dominance, after neutrino decoupling, when neutrinos yield a
relevant contribution to the total energy density and behave as collisionless
ultra-relativistic particles. Besides recovering the standard damping effect
due to neutrinos, a new source term for gravitational waves is shown to arise
from the neutrino anisotropic stress tensor. The importance of such a source
term, so far completely disregarded in the literature, is related to the high
velocity dispersion of neutrinos in the considered epoch; its computation
requires solving the full second-order Boltzmann equation for collisionless
neutrinos.

2
The categories of this paper are: math
9
The categories of this paper are: nlin
4
The categories of this paper are: cond-mat
16
The categories of this paper are: stat
22
The categories of this paper are: chao-dyn
15
The categories of this paper are: nucl-ex
24
The categories of this paper are: dg-ga
1
The categories of this paper are: cs
21
The categories of this paper are: adap-org
5
The categories of this paper are: gr-qc
26
The categories of this paper are: bayes-an
20
The categories of this paper are: acc-phys
3
The categories of this paper are: physics
29
The categories of this paper are: funct-an
17
The categories of this paper are: q-fin
19
The categories of this paper are: eess