In a previous paper we formulated a set of necessary conditions for the spherically symmetric weakly charged dust to avoid Big Bang/Big Crunch, shell crossing and permanent central singularities. However, we did not discuss the properties of the energy density, some of which are surprising and seem not to have been known up to now. A singularity of infinite energy density does exist – it is a p...

We show there exist smooth asymptotically anti-de Sitter initial data which evolve to a big crunch singularity in a low energy supergravity limit of string theory. This opens up the possibility of using the dual conformal field theory to obtain a fully quantum description of the cosmological singularity. A preliminary study of this dual theory suggests that the big crunch is an endpoint of evol...

In a previous paper we formulated a set of necessary conditions for the spherically symmetric weakly charged dust to avoid Big Bang/Big Crunch, shell crossing and permanent central singularities. However, we did not discuss the properties of the energy density, some of which are surprising and seem not to have been known up to now. A singularity of infinite energy density does exist – it is a p...

We describe AlterBBN, a public C program for evaluating the abundances of the elements generated by Big-Bang nucleosynthesis (BBN). This program enables the user to compute the abundances of the elements in the standard model of cosmology, and additionally provides possibilities to alter the assumptions of the cosmological model in order to study their consequences on the abundances of the elem...

We search for viable f R theories of gravity, making use of the equivalence between such theories and scalar-tensor gravity. We find that models can be made consistent with solar system constraints either by giving the scalar a high mass or by exploiting the so-called chameleon effect. However, in both cases, it appears likely that any late-time cosmic acceleration will be observationally indis...

We argue that the Polonyi problem can be avoided when our supersymmetrybreaking vacuum is surrounded by many supersymmetric vacua. We construct a dynamical class of supersymmetry-breaking models to demonstrate our point. These models naturally predict a small deviation from the standard big-bang nucleosynthesis.

0 7 W3R(0), L14R(0), L10R(0), L8R(0), L7R(0), L1R(0), L0R(0) 1 20 L16P(1), L15P(1), L15R(1), W3R(1), L12R(1), L12P(1), W2Q(1), L10R(1), L10P(1), L9R(1), L9P(1), L8P(1), L4R(1), L4P(1), L3R(1), L3P(1), L2R(1), L2P(1), L1R(1), L1P(1) 2 27 L16R(2), L15R(2), L13R(2), L12P(2), W2R(2), W2Q(2), W2P(2), L11R(2), L11P(2), L10P(2), W1R(2), W1Q(2), L9R(2), L9P(2), L8R(2), W0Q(2), L7R(2), L6P(2), L5P(2), L...

A review of the latest measurements of the primordial abundances of the light nuclei D, He, He and Li is given. We discuss in particular the primordial abundance Yp of He as measured in blue compact dwarf galaxies. We argue that the best measurements now give a “high” value of Yp along with a “low” value of D/H, and that the two independent measurements are consistent within the framework of st...

We examine the string cosmology equations with a dilaton potential, contrasting the requirements that the equations and their solutions have the desired a → 1/a pre-big bang symmetry, and give a generic algorithm for obtaining solutions with desired evolutionary properties. This enables us to find pre-big bang type solutions that are regular at t = 0, and with suitable dilaton behaviour. Howeve...