Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A time--dependent Cosmological Constant   We extend the Wald cosmic no-hair theorem to a general class of scalar-tensor
nonminimally coupled theories of gravity where ordinary matter is also present
in the form of a perfect fluid. We give a set of conditions for obtaining a de
Sitter expansion independently of any initial conditions, generalizing the
treatment of such a problem as given by Wald. Finally we apply the results to
some specific models.

18
The categories of this paper are: econ
20
The categories of this paper are: acc-phys
33
The categories of this paper are: plasm-ph
8
The categories of this paper are: hep-ex
31
The categories of this paper are: ao-sci
1
The categories of this paper are: cs
14
The categories of this paper are: math-ph
35
The categories of this paper are: mtrl-th
2
The categories of this paper are: math
28
The categories of this paper are: alg-geom
15
The categories of this paper are: nucl-ex
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The categories of this paper are: solv-int
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The categories of this paper are: bayes-an
17
The categories of this paper are: q-fin
13
The categories of this paper are: quant-ph
37
The categories of this paper are: supr-con