Physics / Fizik

Permanent URI for this collectionhttps://hdl.handle.net/11147/6

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Publisher: search.filters.publisher.Elsevier Ltd.Subject: search.filters.subject.Cosmological constant

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  • Article
    Citation - WoS: 15
    Citation - Scopus: 16
    Stress-Energy Connection and Cosmological Constant Problem
    (Elsevier Ltd., 2011) Demir, Durmuş Ali
    We study gravitational properties of vacuum energy by erecting a geometry on the stress-energy tensor of vacuum, matter and radiation. Postulating that the gravitational effects of matter and radiation can be formulated by an appropriate modification of the spacetime connection, we obtain varied geometrodynamical equations which properly comprise the usual gravitational field equations with, however, Planck-suppressed, non-local, higher-dimensional additional terms. The prime novelty brought about by the formalism is that, the vacuum energy does act not as the cosmological constant but as the source of the gravitational constant. The formalism thus deafens the cosmological constant problem by channeling vacuum energy to gravitational constant. Nevertheless, quantum gravitational effects, if any, restore the problem via the graviton and graviton-matter loops, and the mechanism proposed here falls short of taming such contributions to cosmological constant.
  • Article
    Citation - WoS: 14
    Citation - Scopus: 15
    A Symmetry for Vanishing Cosmological Constant: Another Realization
    (Elsevier Ltd., 2006) Erdem, Recai
    A more conventional realization of a symmetry which had been proposed towards the solution of cosmological constant problem is considered. In this study the multiplication of the coordinates by the imaginary number i in the literature is replaced by the multiplication of the metric tensor by minus one. This realization of the symmetry as well forbids a bulk cosmological constant and selects out 2 (2 n + 1)-dimensional spaces. On contrary to its previous realization the symmetry, without any need for its extension, also forbids a possible cosmological constant term which may arise from the extra-dimensional curvature scalar provided that the space is taken as the union of two 2 (2 n + 1)-dimensional spaces where the usual 4-dimensional space lies at the intersection of these spaces. It is shown that this symmetry may be realized through space-time reflections that change the sign of the volume element. A possible relation of this symmetry to the E-parity symmetry of Linde is also pointed out.