Browsing by Author "Gidelew, Amare Abebe"

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    Beyond the concordance cosmology
    (2013) Gidelew, Amare Abebe; Dunsby, Peter K S
    Includes abstract. Includes bibliographical references.
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    Covariant perturbations in f (R) - gravity of multi-component fluid cosmologies
    (2009) Gidelew, Amare Abebe; Dunsby, Peter K S
    We study the evolution of scalar cosmological perturbations in the 1+3 Covariant Gauge-Invariant formalism for generic f(R) theories of gravity. Working in the energy frame of the total matter, we give a complete set equations describing the evolution of matter and curvature fluctuations for a multi-fluid cosmological medium. We then specialize to a radiation-dust fluid described by barotropic equations of state. We apply the perturbation equations around a background solution of Rⁿ gravity and look at exact solutions for scales much smaller and much larger than the Hubble radius.