Physics / Fizik

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

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Author: search.filters.author.Azri, HemzaWoS Q: search.filters.wosQuartile.Q3

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  • Article
    Citation - WoS: 22
    Citation - Scopus: 24
    Are There Really Conformal Frames? Uniqueness of Affine Inflation
    (World Scientific Publishing Co. Pte Ltd, 2018) Azri, Hemza
    Here, we concisely review the nonminimal coupling dynamics of a single scalar field in the context of purely affine gravity and extend the study to multifield dynamics. The coupling is performed via an affine connection and its associated curvature without referring to any metric tensor. The latter arises a posteriori and it may gain an emergent character like the scale of gravity. What is remarkable in affine gravity is the transition from nonminimal to minimal couplings which is realized by only field redefinition of the scalar fields. Consequently, the inflationary models gain a unique description in this context where the observed parameters, like the scalar tilt and the tensor-to-scalar ratio, are invariant under field reparametrization. Overall, gravity in its affine approach is expected to reveal interesting and rich phenomenology in cosmology and astroparticle physics.
  • Article
    Citation - WoS: 17
    Citation - Scopus: 19
    Cosmological Consequences of a Variable Cosmological Constant Model
    (World Scientific Publishing Co. Pte Ltd, 2017) Azri, Hemza; Bounames, A.
    We derive a model of dark energy which evolves with time via the scale factor. The equation-of-state is studied as a function of a parameter α introduced in this model as = (1 - 2α)/(1 + 2α). In addition to the recent accelerated expansion, the model predicts another decelerated phase. These two phases are studied via the parameter α. The age of the universe is found to be almost consistent with the observation. In the limiting case, the cosmological constant model, we find that vacuum energy gravitates with a tiny gravitational constant which evolves with the scale factor, rather than with Newton's constant. This enables degravitation of the vacuum energy which in turn produces the tiny observed curvature, rather than a 120 orders of magnitude larger value.