ar X iv : a st ro - p h / 96 05 17 6 v 1 2 9 M ay 1 99 6 A time – dependent “ Cosmological Constant ”

ar X iv : a st ro - p h / 93 05 00 2 v 1 6 M ay 1 99 3 Visibility of Gravitational Lenses and the Cosmological Constant Problem

Recent observations suggest appreciable star formation activity in early-type galaxies down to redshift z ∼ 0.5. If so, there is likely to be dust in these galaxies. We consider the possibility that obscuration by dust can reconcile the observed frequency of gravitational lensing of quasar images with the considerably larger rate predicted in a low density cosmologically flat universe dominated...

ar X iv : a st ro - p h / 99 05 37 6 v 1 2 8 M ay 1 99 9 A 6 . 4 - hr positive superhump period in TV

ar X iv : a st ro - p h / 96 05 07 0 v 1 1 4 M ay 1 99 6 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 spe...

X iv : a st ro - p h / 06 05 17 3 v 1 6 M ay 2 00 6 Why the cosmological constant is small and positive

Within conventional big bang cosmology, it has proven to be very difficult to understand why today’s cosmological constant is so small. In this paper, we show that a cyclic model of the universe can naturally incorporate a dynamical mechanism that automatically relaxes the value of the cosmological constant, taking account of contributions to the vacuum density at all energy scales. Because the...

X iv : a st ro - p h / 06 05 17 3 v 1 6 M ay 2 00 6 Why the cosmological constant is small and positive Paul

Within conventional big bang cosmology, it has proven to be very difficult to understand why today’s cosmological constant is so small. In this paper, we show that a cyclic model of the universe can naturally incorporate a dynamical mechanism that automatically relaxes the value of the cosmological constant, taking account of contributions to the vacuum density at all energy scales. Because the...