Physics / Fizik

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

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Scopus Q: search.filters.scopusQuartile.Q1Subject: search.filters.subject.Vacuum energy

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  • Article
    Citation - WoS: 47
    Citation - Scopus: 42
    Affine Inflation
    (American Physical Society, 2017) Azri, Hemza; Demir, Durmuş Ali
    Affine gravity, a gravity theory based on affine connection with no notion of metric, supports scalar field dynamics only if scalar fields have nonvanishing potential. The nonvanishing vacuum energy ensures that the cosmological constant is nonvanishing. It also ensures that the energy-momentum tensor of vacuum gives the dynamically generated metric tensor. We construct this affine setup and study primordial inflation in it. We study inflationary dynamics in affine gravity and general relativity, comparatively. We show that nonminimally coupled inflaton dynamics can be transformed into minimally coupled ones with a modified potential. We also show that there is one unique frame in affine gravity, as opposed to the Einstein and Jordan frames in general relativity. Future observations with higher accuracy may be able to test affine gravity.
  • Article
    Citation - WoS: 12
    Citation - Scopus: 12
    Eddington's Gravity in Immersed Spacetime
    (IOP Publishing Ltd., 2015) Azri, Hemza
    We formulate Eddington's affine gravity in a spacetime that is immersed in a larger eight-dimensional space endowed with a hypercomplex structure. The dynamical equation of the first immersed Ricci-type tensor leads to gravitational field equations which include matter. We also study the dynamical effects of the second Ricci-type tensor when added to the Lagrangian density. A simple Lagrangian density constructed from a combination of the standard Ricci tensor and a new tensor field that appears due to the immersion, leads to gravitational equations in which the vacuum energy gravitates with a different cosmological strength as in Demir (2014 Phys. Rev. D 90 064017), rather than with Newton's constant. As a result, the tiny observed curvature is reproduced due to large hierarchies rather than fine tuning.