Physics / Fizik

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

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Institution Author: search.filters.institutionAuthor.Erdem, RecaiSubject: search.filters.subject.Dimensions

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Now showing 1 - 4 of 4
  • 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.
  • Article
    Citation - WoS: 3
    Citation - Scopus: 3
    Reconsidering extra time-like dimensions
    (Springer Verlag, 2006) Erdem, Recai; Ün, Cem Salih
    In this study we reconsider the phenomenological problems related to tachyonic modes in the context of extra time-like dimensions. First we reconsider a lower bound on the size of extra time-like dimensions and improve on the conclusion in the literature. Next we discuss the issues of spontaneous decay of stable fermions through tachyonic decays and disappearance of fermions due to tachyonic contributions to their self-energies. We find that the tachyonic modes due to extra time-like dimensions are less problematic than the tachyonic modes in the usual 4-dimensional setting because the most troublesome Feynman diagrams are forbidden once the conservation of momentum in the extra time-like dimensions is imposed.
  • Conference Object
    Citation - WoS: 22
    Citation - Scopus: 23
    A Symmetry for Vanishing Cosmological Constant in an Extra-Dimensional Toy Model
    (Elsevier, 2005) Erdem, Recai
    We introduce a symmetry principle that forbids a bulk cosmological constant in six and ten dimensions. Then the symmetry is extended in six dimensions so that it insures absence of 4-dimensional cosmological constant induced by the six-dimensional curvature scalar, at least, for a class of metrics. A small cosmological constant may be induced in this scheme by breaking of the symmetry by a small amount.
  • Article
    Citation - WoS: 3
    Citation - Scopus: 2
    Fermion Families and Chirality Through Extra Dimensions
    (Springer Verlag, 2002) Erdem, Recai
    We give a simple model to explain the origin of fermion families and chirality through the use of a domain wall-anti-domain wall pair placed in a five dimensional space-time. Higher dimensional spaces have been revived in the last years by the hope that the extra space dimensions other than the usual three dimensions may be experimentally accessible in the near future...