2006 (IPP)

Permanent URI for this collectionhttp://localhost:4000/handle/11007/335

Browse

Author: search.filters.author.Sami, M.Subject: search.filters.subject.Dark energy

Search Results

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Dark energy cosmology from higher-order, string-inspired gravity, and its reconstruction
    (2006-04-10) Nojiri, Shin'ichi; Odintsov, Sergi D.; Sami, M.
    In this paper we investigate the cosmological effects of modified gravity with string curvature corrections added to the Einstein-Hilbert action in the presence of a dynamically evolving scalar field coupled to Riemann invariants. The scenario exhibits several features of cosmological interest for the late universe. We show that higher-order stringy corrections can lead to a class of dark energy models consistent with recent observations. The models can give rise to quintessence without recourse to a scalar field potential. The detailed treatment of the reconstruction program for general scalar-Gauss-Bonnet gravity is presented for any given cosmology. The explicit examples of reconstructed scalar potentials are given for an accelerated (quintessence, cosmological constant, or phantom) universe. Finally, the relation with modified F G gravity is established at the classical level and is extended to include third order terms on the curvature.
  • No Thumbnail Available
    Item
    Dynamics of dark energy
    (2006-06-16) Copeland, E. J.; Sami, M.; Tsujikawa, Shinji
    In this paper we review in detail a number of approaches that have been adopted to try and explain the remarkable observation of our accelerating Universe. In particular we discuss the arguments for and recent progress made towards understanding the nature of dark energy. We review the observational evidence for the current accelerated expansion of the universe and present a number of dark energy models in addition to the conventional cosmological constant, paying particular attention to scalar field models such as quintessence, K-essence, tachyon, phantom and dilatonic models. The importance of cosmological scaling solutions is emphasized when studying the dynamical system of scalar fields including coupled dark energy. We study the evolution of cosmological perturbations allowing us to confront them with the observation of the Cosmic Microwave Background and Large Scale Structure and demonstrate how it is possible in principle to reconstruct the equation of state of dark energy by also using Supernovae Ia observational data. We also discuss in detail the nature of tracking solutions in cosmology, particle physics and braneworld models of dark energy, the nature of possible future singularities, the effect of higher order curvature terms to avoid a Big Rip singularity, and approaches to modifying gravity which leads to a late-time accelerated expansion without recourse to a new form of dark energy.