Results 21 to 30 of about 310,039 (247)

Constraining inflationary scenarios with braneworld models and second order cosmological perturbations [PDF]

open access: yes, 2010
PhDInflationary cosmology is the leading explanation of the very early universe. Many different models of inflation have been constructed which fit current observational data.
Huston, Ian
core   +4 more sources

Unified Dark Matter models with fast transition [PDF]

open access: yes, 2010
We investigate the general properties of Unified Dark Matter (UDM) fluid models where the pressure and the energy density are linked by a barotropic equation of state (EoS) p = p(ρ) and the perturbations are adiabatic.
Davide Pietrobon   +12 more
core   +3 more sources

Matching conditions for cosmological perturbations [PDF]

open access: yesPhysical Review D, 1995
We derive the matching conditions for cosmological perturbations in a Friedmann Universe where the equation of state undergoes a sharp jump, for instance as a result of a phase transition. The physics of the transition which is needed to follow the fate of the perturbations is clarified.
Deruelle, Nathalie, Mukhanov, V. F.
openaire   +3 more sources

COSMOLOGICAL PERTURBATIONS IN RENORMALIZATION GROUP DERIVED COSMOLOGIES [PDF]

open access: yesInternational Journal of Modern Physics D, 2004
A linear cosmological perturbation theory of an almost homogeneous and isotropic perfect fluid Universe with dynamically evolving Newton constant G and cosmological constant Λ is presented. A gauge invariant formalism is developed by means of the covariant approach, and the acoustic propagation equations governing the evolution of the comoving ...
Bonanno, A., Reuter, M.
openaire   +3 more sources

The dynamics of cosmological scenarios inspired by quantum gravity [PDF]

open access: yes, 2006
PhDIn this thesis we study the dynamics of cosmological scenarios inspired by quantum gravity. Part I investigates novel features of the semi-classical regime of homogeneous and isotropic loop quantum cosmology.
Mulryne, David James
core   +4 more sources

Cosmological perturbations [PDF]

open access: yesPhysics Reports, 2009
We review the study of inhomogeneous perturbations about a homogeneous and isotropic background cosmology. We adopt a coordinate based approach, but give geometrical interpretations of metric perturbations in terms of the expansion, shear and curvature of constant-time hypersurfaces and the orthogonal timelike vector field.
Malik, KA, Wands, D
openaire   +3 more sources

The viability of modified gravity theories [PDF]

open access: yes, 2009
PhDThis thesis studies the viability of classes of modified gravity (MG) theories based on generalisations of the Einstein-Hilbert action. Particular emphasis is given to f(R) theories in both the metric and Palatini formalisms, scalar-tensor theories ...
Uddin, Kotub
core   +3 more sources

Cosmological perturbations in Palatini formalism [PDF]

open access: yesJournal of Cosmology and Astroparticle Physics, 2021
29 pages, Comments welcome!
Yamaguchi, Masahide   +3 more
openaire   +3 more sources

Evolution of second-order cosmological perturbations. [PDF]

open access: yes, 1984
We present a method for constructing gauge-invariant cosmological perturbations which are gauge-invariant up to second order. As an example, we give the gauge-invariant definition of the second-order curvature perturbation on uniform density ...
Blair, D   +999 more
core   +6 more sources

The mass of cosmological perturbations in Loop Quantum Cosmology

open access: yesThe Fifteenth Marcel Grossmann Meeting, 2022
Sixth Tux workshop on Quantum Gravity. Monday, February 19 to Friday, February 23. Tux, Austria (2018). ..-https://www.gravity.physik.fau.de/events/tux6/
Mena Marugán, Guillermo A.   +2 more
openaire   +2 more sources

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