Published in the International Journal of Modern Physics
D, Volume 9, Issue 04, pp. 373-443 (2000).
For a PDF version of the article, click
here.
For a Postscript version of the article, click
here.
THE CASE FOR A POSITIVE COSMOLOGICAL LAMBDA-TERM
Varun Sahni
IUCAA - Inter-University Centre for Astronomy & Astrophysics, Post Bag
4, Ganeshkind, Pune 411007, India
and
Alexei Starobinsky
Landau Institute for Theoretical Physics, Kosygina 2, Moscow 117334,
Russia
Abstract. Recent observations of Type 1a supernovae indicating an
accelerating universe have once more drawn attention to the
possible existence, at the present epoch, of a small positive
-term
(cosmological constant). In this paper we
review both observational and theoretical aspects of a small cosmological
-term. We discuss
the current observational situation focusing on cosmological tests of
including the age
of the universe, high redshift supernovae,
gravitational lensing, galaxy clustering and the
cosmic microwave background. We also review the theoretical debate
surrounding :
the generation of
in models with spontaneous symmetry breaking and
through quantum vacuum polarization effects - mechanisms
which are known to give rise to a
large value of
hence leading to the `cosmological constant problem'.
More recent attempts to generate a small
cosmological constant at the present epoch using either field theoretic
techniques, or by modeling a dynamical
-term
by scalar fields are also extensively discussed. Anthropic
arguments favouring a small
-term are briefly
reviewed. A comprehensive bibliography of recent work
on is provided.
Table of Contents
0
= 1)
)