Bouncing Galileon Cosmologies
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In this article, nonsingular, homogeneous and isotropic bouncing solutions of the conformal Galileon model were presented, and it was shown that such solutions necessarily begin with a radiation-dominated contracting phase.Abstract:
We present nonsingular, homogeneous and isotropic bouncing solutions of the conformal Galileon model. We show that such solutions necessarily begin with a radiation-dominated contracting phase. This is followed by a quintom scenario in which the background equation of state crosses the cosmological constant boundary allowing for a nonsingular bounce which in turn is followed by Galilean Genesis. We analyze the spectrum of cosmological perturbations in this background. Our results show that the fluctuations evolve smoothly and without any pathology, but the adiabatic modes form a blue tilted spectrum. In order to achieve a scale-invariant primordial power spectrum as required by current observations, we introduce a light scalar field coupling to the Galileon kinetically. We find two couplings which yield a scale-invariant spectrum, one of which requires a fine tuning of the initial conditions. This model also predicts a blue tilted spectrum of gravitational waves stemming from quantum vacuum fluctuations in the contracting phase.read more
Citations
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Galileons in the Sky
Claudia de Rham,Claudia de Rham +1 more
TL;DR: The existence of a non-renormalization theorem for Galileon scalar fields makes them especially attractive candidates for inflation as well as for late-time acceleration in braneworld models as mentioned in this paper.
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Stability of the Einstein static universe in f ( R , T ) gravity
Hamid Shabani,Amir Hadi Ziaie +1 more
TL;DR: In this article, the existence and stability of an ES universe in the context of f(R, T) modified theories of gravity is studied. And the authors suggest that modifications in f(T, R) gravity would lead to stable solutions which are unstable in f (R) gravity model and also investigate homogeneous scalar perturbations for the mentioned models.
Journal ArticleDOI
Two Field Matter Bounce Cosmology
TL;DR: In this article, the authors re-examine the non-singular matter bounce scenario and study the evolution of both curvature and entropy fluctuations through the bounce, and show that both have a scale-invariant spectrum which is blue-tilted on small scales.
Journal ArticleDOI
Evolution of cosmological perturbations and the production of non-Gaussianities through a nonsingular bounce: Indications for a no-go theorem in single field matter bounce cosmologies
TL;DR: In this article, the authors studied the dynamics of the cosmological perturbations evolving through a nonsingular bouncing phase described by a generic single scalar field Lagrangian minimally coupled to Einstein gravity.
Journal ArticleDOI
Unbraiding the bounce: superluminality around the corner
David A. Dobre,Andrei V. Frolov,José T. Gálvez Ghersi,José T. Gálvez Ghersi,Sabir Ramazanov,Alexander Vikman +5 more
TL;DR: In this paper, the cosmological bounce solution of Ijjas and Steinhardt was studied and the exact structure of the Lagrangian was reconstructed for a possible UV-completion.
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