Early-universe cosmology in Einstein-scalar-Gauss-Bonnet gravity
arXiv:1708.01150
Abstract
Theoretical arguments and cosmological observations suggest that Einstein's theory of general relativity needs to be modified at high energies. One of the best motivated higher-curvature extensions of general relativity is Einstein-scalar-Gauss-Bonnet gravity, in which a scalar field is coupled to quadratic curvature invariants. This theory is inspired by an effective string-theory model and its predictions dramatically differ from Einstein's theory in high-curvature regions - such as the interior of black holes and the early universe - where it aims at resolving curvature singularities. In this work we derive cosmological solutions in Einstein-scalar-Gauss-Bonnet gravity for quadratic and for exponential coupling functions, and for any spatial curvature. We discuss already known solutions and find new nonsingular, inflationary, and bouncing solutions. We study the linear stability of these solutions and the absence of ghosts, finding that all the aforementioned solutions are unstable against tensor perturbations. We then introduce a simple, quadratic potential for the scalar field. In some cases the presence of a mass term cures the tensor instability. The proposed model is therefore a viable and attractive candidate for inflation, and one in which the scalar field is naturally provided by the gravitational sector.
arXiv commentMaster thesis, 118 pages, 84 figures
References in corpus (19)
- Modified Gravity and Cosmology
- The Confrontation between General Relativity and Experiment
- The Ekpyrotic Universe: Colliding Branes and the Origin of the Hot Big Bang
- Testing General Relativity with Present and Future Astrophysical Observations
- On gravitational-wave spectroscopy of massive black holes with the space interferometer LISA
- Dilatonic Black Holes in Higher Curvature String Gravity
- Gravitational Wave Tests of General Relativity with Ground-Based Detectors and Pulsar Timing Arrays
- Are black holes in alternative theories serious astrophysical candidates? The case for Einstein-Dilaton-Gauss-Bonnet black holes
- Dilatonic Black Holes with Gauss-Bonnet Term
- Charged black holes in effective string theory
- Slowly rotating black holes in alternative theories of gravity
- Singularity-free cosmological solutions in quadratic gravity
- Slow-roll inflation with a Gauss-Bonnet correction
- Gauss-Bonnet Inflation
- Inflation coupled to a Gauss-Bonnet term
- The graceful exit in pre-big bang string cosmology
- A tensor instability in the Eddington inspired Born-Infeld Theory of Gravity
- On the existence of singularity-free solutions in quartic gravity
- Early-time cosmological solutions in Einstein-scalar-Gauss-Bonnet theory