Bouncing universes in string-inspired gravity

  title={Bouncing universes in string-inspired gravity},
  author={Tirthabir Biswas and Anupam Mazumdar and Warren Siegel},
  journal={Journal of Cosmology and Astroparticle Physics},
  pages={009 - 009}
We consider the effects on cosmology of higher derivative modifications of gravity that make it asymptotically free without introducing ghosts. The weakening of gravity at short distances allows pressure to prevent a singularity, producing a solution with contraction preceding expansion. 

On bouncing solutions in non-local gravity

A non-local modified gravity model with an analytical function of the d’Alembert operator, is considered. This model has been recently proposed as a possible way of resolving the singularities

Speed of Sound in String Gas Cosmology

We consider an ensemble of closed strings in a compact space with stable one cycles and compute the speed of sound resulting from string thermodynamics. Possible applications to the issue of Jeans

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Towards resolution of anisotropic cosmological singularity in infinite derivative gravity

In this paper, we will show that the equations of motion of the quadratic in curvature, ghost free, infinite derivative theory of gravity will not permit an anisotropic collapse of a homogeneous

On Nonlocal Modified Gravity and Cosmology

Despite many nice properties and numerous achievements, general relativity is not a complete theory. One of actual approaches towards more complete theory of gravity is its nonlocal modification. We

Stable analytic bounce in non-local Einstein–Gauss–Bonnet cosmology

We consider the most general quadratic in curvature stringy-motivated non-local action for the modified Einstein's gravity. We present exact analytic cosmological solutions including the bouncing

Bouncing cosmology in three dimensions

We consider a dynamical two-brane in a four-dimensional black hole background with scalar hair. At high temperature this black hole goes through a phase transition by radiating away the scalar. The

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We find nonperturbative solutions of a nonlocal scalar field equation, with cubic or exponential potential on a cosmological background. The former case corresponds to the lowest level effective



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We consider general curvature-invariant modifications of the Einstein-Hilbert action that become important only in regions of extremely low space-time curvature. We investigate the far future

Gravitational couplings of the inflaton in extended inflation.

We discuss a new extended-inflationary scenario evading the difficulties of the original model. Our model can thermalize the energy in the bubble walls by the necessary epoch, and establish a

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We study spatially homogeneous and isotropic solutions to the equations of motion derived from dilaton gravity, in the presence of a special combination of higher derivative terms in the

One-loop superstring cosmology and the nonsingular universe.

  • EastherMaeda
  • Physics
    Physical review. D, Particles and fields
  • 1996
This work finds nonsingular solutions which interpolate between a contracting universe and an expanding universe, and shows that these solutions provide a mechanism for removing the initial conditions problem peculiar to spatially closed FRW cosmologies.

Nonsingular dilaton cosmology in the string frame

We consider the theory obtained by adding to the usual string frame dilaton gravity action specially constructed higher derivative terms motivated by the limited curvature construction of [1] and