Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Adiabatic and entropy perturbations from inflation   We study adiabatic (curvature) and entropy (isocurvature) perturbations
produced during a period of cosmological inflation that is driven by multiple
scalar fields with an arbitrary interaction potential. A local rotation in
field space is performed to separate out the adiabatic and entropy modes. The
resulting field equations show explicitly how on large scales entropy
perturbations can source adiabatic perturbations if the background solution
follows a curved trajectory in field space, and how adiabatic perturbations
cannot source entropy perturbations in the long-wavelength limit. It is the
effective mass of the entropy field that determines the amplitude of entropy
perturbations during inflation. We present two applications of the equations.
First, we show why one in general expects the adiabatic and entropy
perturbations to be correlated at the end of inflation, and calculate the
cross-correlation in the context of a double inflation model with two
non-interacting fields. Second, we consider two-field preheating after
inflation, examining conditions under which entropy perturbations can alter the
large-scale curvature perturbation and showing how our new formalism has
advantages in numerical stability when the background solution follows a
non-trivial trajectory in field space.

37
The categories of this paper are: supr-con
3
The categories of this paper are: physics
2
The categories of this paper are: math
33
The categories of this paper are: plasm-ph
27
The categories of this paper are: comp-gas
22
The categories of this paper are: chao-dyn
18
The categories of this paper are: econ
21
The categories of this paper are: adap-org
4
The categories of this paper are: cond-mat
24
The categories of this paper are: dg-ga
35
The categories of this paper are: mtrl-th
32
The categories of this paper are: atom-ph
11
The categories of this paper are: hep-lat
36
The categories of this paper are: cmp-lg
20
The categories of this paper are: acc-phys
19
The categories of this paper are: eess