Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On disc protoplanet interactions in a non-barotropic disc with thermal
  diffusion   We study the disc planet interactions of low-mass protoplanets embedded in a
circumstellar disc. We extend the standard theory of planet migration from the
usual locally isothermal assumption to include non-barotropic effects, focusing
on the validity of linear theory. We compared solutions of the linear equations
with results from non-linear hydrodynamic simulations, where in both cases we
adopted a background entropy gradient and solved the energy equation. We show
that the migration behavior of embedded planets depends critically on the
background radial entropy gradient in the disc. The presence of such a gradient
not only changes the corotation torque on the planet, but also always
guarantees a departure from linear behavior, which gives a singular density
response at corotation, in the absence of thermal or viscous diffusion. A
negative entropy gradient tends to give rise to positive, non-linear corotation
torques apparently produced as material executes horseshoe turns at
approximately constant entropy. These torques have no counterpart in linear
theory, but can be strong enough to push the planet outwards until saturation
starts to occur after a horseshoe libration period. Increased thermal diffusion
acts to reduce these non-linear torques, but, at the same time, it can help to
prevent their saturation. In combination with a small kinematic viscosity that
is able to maintain a smooth density profile the positive torque could be
sustained.

12
The categories of this paper are: nucl-th
13
The categories of this paper are: quant-ph
37
The categories of this paper are: supr-con
25
The categories of this paper are: patt-sol
21
The categories of this paper are: adap-org
36
The categories of this paper are: cmp-lg
0
The categories of this paper are: hep-ph
9
The categories of this paper are: nlin
30
The categories of this paper are: q-alg
34
The categories of this paper are: chem-ph
8
The categories of this paper are: hep-ex
2
The categories of this paper are: math
18
The categories of this paper are: econ
10
The categories of this paper are: q-bio
28
The categories of this paper are: alg-geom
27
The categories of this paper are: comp-gas