Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Unified first law and some general prescription: a redefinition of
  surface gravity   The paper contains an extensive study of the unified first law (UFL) in the
Friedmann-Robertson-Walker spacetime model. By projecting the UFL along the
Kodama vector the second Friedmann equation can be obtained. Also studying the
UFL on the event horizon it is found that Clausius relation cannot be obtained
from the UFL by projecting it along the tangent to the event horizon as it can
be for the trapping horizon. However, it is shown in the present work that
Clausius relation can be obtained by projecting the UFL along the Kodama vector
on the horizon and the result is found to be true for any horizon. Finally
motivated by the Unruh temperature for the Rindler observer, surface gravity is
redefined and a Clausius relation is obtained from the UFL by projecting it
along a vector analogous to the Kodama vector.

0
The categories of this paper are: hep-ph
4
The categories of this paper are: cond-mat
6
The categories of this paper are: astro-ph
1
The categories of this paper are: cs
23
The categories of this paper are: solv-int
9
The categories of this paper are: nlin
18
The categories of this paper are: econ
26
The categories of this paper are: bayes-an
7
The categories of this paper are: hep-th
22
The categories of this paper are: chao-dyn
37
The categories of this paper are: supr-con
36
The categories of this paper are: cmp-lg
28
The categories of this paper are: alg-geom
3
The categories of this paper are: physics
17
The categories of this paper are: q-fin
2
The categories of this paper are: math