Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Diffusion in the general theory of relativity   The Markovian diffusion theory in the phase space is generalized within the
framework of the general theory of relativity. The introduction of moving
orthonormal frame vectors both for the position as well the velocity space
enables to bypass difficulties in the general relativistic stochastic calculus.
The general relativistic Kramers equation in the phase space is derived both in
the parametrization of phase space proper time and the coordinate time. The
transformation of the obtained diffusion equation under hypersurface-preserving
coordinate transformations is analyzed and diffusion in the expanding universe
is studied. It is shown that the validity of the fluctuation-dissipation
theorem ensures that in the quasi-steady state regime the result of the derived
diffusion equation is consistent with the kinetic theory in thermodynamic
equilibrium.

22
The categories of this paper are: chao-dyn
17
The categories of this paper are: q-fin
14
The categories of this paper are: math-ph
30
The categories of this paper are: q-alg
31
The categories of this paper are: ao-sci
35
The categories of this paper are: mtrl-th
29
The categories of this paper are: funct-an
12
The categories of this paper are: nucl-th
18
The categories of this paper are: econ
2
The categories of this paper are: math
9
The categories of this paper are: nlin
20
The categories of this paper are: acc-phys
10
The categories of this paper are: q-bio
37
The categories of this paper are: supr-con
1
The categories of this paper are: cs
0
The categories of this paper are: hep-ph