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Now showing items 11-20 of 27
Classical and quantum solutions in Brans-Dicke cosmology with a perfect fluid
(American Physical SocietyPhysical Review D, 2016)
We consider the application of group invariant transformations in order to constrain a flat isotropic and homogeneous cosmological model, containing of a Brans-Dicke scalar field and a perfect fluid with a constant equation ...
Evolution of cyclic mixmaster universes with noncomoving radiation
We study a model of a cyclic, spatially homogeneous, anisotropic mixmaster universe of Bianchi type IX 'mixmaster' universe, containing the a radiation field with non-comoving ('tilted' with respect to the tetrad frame of ...
New integrable models and analytical solutions in f(R) cosmology with an ideal gas
(American Physical SocietyPhysical Review D - Particles, Fields, Gravitation and Cosmology, 2018-01-23)
In the context of f(R)-gravity with a spatially flat FLRW metric containing an ideal fluid, we use the method of invariant transformations to specify families of models which are integrable. We find three families of f(R) ...
Relativistic magnetised perturbations: Magnetic pressure versus magnetic tension
(IoPClassical and Quantum Gravity, 2018-05-16)
We study the linear evolution of magnetised cosmological perturbations in the post-recombination epoch. Using full general relativity and adopting the ideal magnetohydrodynamic approximation, we refine and extend the ...
Dynamical analysis in scalar field cosmology
(APSPhysical Review D, 2015-06-23)
We give a general method to find exact cosmological solutions for scalar-field dark energy in the presence of perfect fluids. We use the existence of invariant transformations for the Wheeler De Witt (WdW) equation. We ...
Local varying-alpha theories
(World Scientific PublishingModern Physics Letters A, 2015-07-20)
In a recent paper, we demonstrated how the simplest model for varying-alpha may be interpreted as the effect of a dielectric material, generalized to be consistent with Lorentz invariance. Unlike normal dielectrics, such ...
Hyperbolic Inflation in the Light of Planck 2015 data
(APSPhysical Review D, 2015-05-18)
Rubano and Barrow have discussed the emergence of a dark energy, with late-time cosmic acceleration arising from a self-interacting homogeneous scalar field with a potential of hyperbolic power type. Here, we study the ...
Singular Inflation
(APSPhysical Review D, 2015-04-08)
We prove that a homogeneous and isotropic universe containing a scalar field with a power-law potential, V(ϕ)=Aϕ^n, with 0<n<1 and A>0 always develops a finite-time singularity at which the Hubble rate and its first ...
New Singularities in Unexpected Places
(World ScientificInternational Journal of Modern Physics D, 2015-09-28)
Spacetime singularities have been discovered which are physically much weaker than those predicted by the classical singularity theorems. Geodesics evolve through them and they only display infinities in the derivatives ...
Turning on gravity with the Higgs mechanism
(IOP PublishingClassical and Quantum Gravity, 2016-06-21)
We investigate how a Higgs mechanism could be responsible for the
emergence of gravity in extensions of Einstein theory, with a suitable low energy limit.
In this scenario, at high energies, symmetry restoration could "turn ...