Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Systematics of Adiabatic Modes: Flat Universes   Adiabatic modes are cosmological perturbations that are locally
indistinguishable from a (large) change of coordinates. At the classical level,
they provide model independent solutions. At the quantum level, they lead to
soft theorems for cosmological correlators. We present a systematic derivation
of adiabatic modes in spatially-flat cosmological backgrounds with
asymptotically-perfect fluids. We find several new adiabatic modes including
vector, time-dependent tensor and time-dependent scalar modes. The new vector
and tensor modes decay with time in standard cosmologies but are the leading
modes in contracting universes. We present a preliminary derivation of the
related soft theorems. In passing, we discuss a distinction between classical
and quantum adiabatic modes, we clarify the subtle nature of Weinberg second
adiabatic mode and point out that the adiabatic nature of a perturbation is a
gauge dependent statement.

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The categories of this paper are: hep-ex
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The categories of this paper are: cond-mat
3
The categories of this paper are: physics
19
The categories of this paper are: eess
1
The categories of this paper are: cs
18
The categories of this paper are: econ
9
The categories of this paper are: nlin
37
The categories of this paper are: supr-con
10
The categories of this paper are: q-bio
34
The categories of this paper are: chem-ph
24
The categories of this paper are: dg-ga
0
The categories of this paper are: hep-ph
35
The categories of this paper are: mtrl-th
32
The categories of this paper are: atom-ph
33
The categories of this paper are: plasm-ph
30
The categories of this paper are: q-alg