It is now about 10 years since the evidence, based on Type Ia supernovae, for the acceleration of the expansion of the Universe was discovered. I will discuss some aspects of the work and events in the Supernova Cosmology Project (SCP), during the period 1988 to 1998, which led to this discovery. Talk presented at Dark Matter Conference DM08, Marina del Rey, Feb. 20, 2008.

We construct dark halo models which are supported by a self-interacting scalar field. The possibility that the energy density of such a field which could produce dark matter and dark energy inside and outside of the galactic dark halos is explored. c © Electronic Journal of Theoretical Physics. All rights reserved.

Considering gravitino dark matter scenarios, we obtain the full gauge-invariant result for the relic density of thermally produced gravitinos to leading order in the Standard Model gauge couplings. For the temperatures required by thermal leptogenesis, we find gaugino mass bounds which will be probed at future colliders. We show that a conceivable determination of the gravitino mass will allow ...

In this talk, I will present highlights of a recent model of dark energy and dark matter in which the present universe is " trapped " in a false vacuum described by the potential of an axion-like scalar field (the acceleron) which is related to a new strong interaction gauge sector, SU (2) Z , characterized by a scale Λ Z ∼ 3 × 10 −3 eV. This false vacuum model mimicks the ΛCDM scenario. In add...

A cosmology is considered driven by a stress-energy tensor consisting of perfect fluid, tachyonic dust and a cosmological constant. The inflationary, radiation dominated and matter dominated eras are investigated in detail. In all three eras, the tachyonic pressure decreases with increasing radius of the universe and is thus minimal in the matter dominated era. The gravitational effects of the ...

In minimal SUSY GUT models the R-parity breaking terms are severely constrained by SU(5) gauge invariance. We consider the particular case where the explicit R-parity breaking occurs only via dimension 2 terms of the superpotential. This model possesses only three R-parity breaking parameters. We have studied the predictions of this model for the neutrino masses and mixing angles at the one-loo...

A review of the study of dark matter and large scale structure of the Universe at Tartu Observatory is given. Tartu astronomers have participated in this development, starting from Ernst Öpik and Grigori Kuzmin, and continuing with the present generation of astronomers. Our goal was to understand better the structure, origin and evolution of the Universe.

We revisit the implications of the R-invariant New Inflation model to the supersymmetric standard model in light of recent discussion of gravitino production processes by the decay of the inflaton or the supersymmetry breaking field. We show that the models with supergravity mediation do not go well with the R-invariant New Inflation model, where the gravitino abundance produced by the decay of...

By including the effects of superstring thresholds, we reconsider minimal string unification together with the requirement of producing a supersymmetry-breaking gluino condensate in the hidden sector. This gives, for examples of phenomenologically-viable Z ′ 8 and other related orbifolds, the constraint that 0.1215 ≤ αs(MZ) ≤ 0.1270. In such models, a hidden photino can be a source of cosmologi...