Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Back-reaction of Quantum fields in an Einstein Universe   We study the back-reaction effects of the finite-temperature scalar field and
the photon field in the background of an Einstein universe. In each case we
find a relation between the temperature of the universe and its radius. These
relations exhibit a minimum radius below which no self-consistent solution for
the Einstein field equation can be found. A maximum temperature marks the
transition from the vacuum dominated era to the radiation dominated era. An
interpretation to this behavior in terms of Bose-Einstein condensation in the
case of the scalar field is given.

37
The categories of this paper are: supr-con
28
The categories of this paper are: alg-geom
14
The categories of this paper are: math-ph
24
The categories of this paper are: dg-ga
19
The categories of this paper are: eess
18
The categories of this paper are: econ
21
The categories of this paper are: adap-org
27
The categories of this paper are: comp-gas
20
The categories of this paper are: acc-phys
13
The categories of this paper are: quant-ph
12
The categories of this paper are: nucl-th
8
The categories of this paper are: hep-ex
26
The categories of this paper are: bayes-an
1
The categories of this paper are: cs
22
The categories of this paper are: chao-dyn
30
The categories of this paper are: q-alg