Cosmology with a light ghost
arXiv:1610.05330 · doi:10.1088/1475-7516/2016/12/018
Abstract
We study the creation and evolution of cosmological perturbations in renormalizable quadratic gravity with a Weyl term. We adopt a prescription that implies the stability of the vacuum at the price of introducing a massive spin-two ghost state, leading to the loss of unitarity. The theory may still be predictive regardless the interpretation of non-unitary processes provided that their rate is negligible compared to the Universe expansion rate. This implies that the ghost is effectively stable. In such a setup, there are two scalar degrees of freedom excited during inflation. The first one is the usual curvature perturbation whose power spectrum appears to coincide with that of single-field inflation. The second one is a scalar component of the ghost encoded in the shift vector of the metric in the uniform inflaton gauge. The amplitudes of primordial tensor and vector perturbations are strongly suppressed. After inflation the ghost field starts to oscillate and its energy density shortly becomes dominant in the Universe. For all ghost masses allowed by laboratory constraints ghosts should have "overclosed" the Universe at temperatures higher than that of primordial nucleosynthesis. Thus, the model with the light Weyl ghost is ruled out.
26 pages, 1 figure, minor corrections, published version
References in corpus (34)
- f(R) theories
- Quantum Gravity at a Lifshitz Point
- A healthy extension of Horava gravity
- Models of non-relativistic quantum gravity: the good, the bad and the healthy
- On the Extra Mode and Inconsistency of Horava Gravity
- Agravity
- Improved constraints on non-Newtonian forces at 10 microns
- Constraints on Einstein-Æther theory and Horava gravity from binary pulsar observations
- Einstein Gravity from Conformal Gravity
- Dynamically Induced Planck Scale and Inflation
- Occurrence of exact inflation in non-local UV-complete gravity
- Cosmological perturbations from multi-field inflation in generalized Einstein theories
- Renormalization of Horava Gravity
- On the evolution of universes in quadratic theories of gravity
- Causality as an emergent macroscopic phenomenon: The Lee-Wick O(N) model
- Scalaron the mighty: producing dark matter and baryon asymmetry at reheating
- Quantum mechanics of 4-derivative theories
- Search for magnetic monopoles with the MoEDAL prototype trapping detector in 8 TeV proton-proton collisions at the LHC
- The Theorem of Ostrogradsky
- Universal scaling properties of extremal cohesive holographic phases
- Naturalness and Dimensional Transmutation in Classically Scale-Invariant Gravity
- Phenomenology of theories of gravity without Lorentz invariance: the preferred frame case
- Testing Lorentz invariance of dark matter
- Cosmological perturbation theory
- Cosmological constraints on deviations from Lorentz invariance in gravity and dark matter
- Technically natural dark energy from Lorentz breaking
- Inflation with a Weyl term, or ghosts at work
- Tensor ghosts in the inflationary cosmology
- Primordial massive gravitational waves from Einstein-Chern-Simons-Weyl gravity
- Stable super-inflating cosmological solutions in f(R)-gravity
- UV-extending Ghost Inflation
- Covariant Linear Perturbation Formalism
- A conformal model of gravitons
- Scale-invariant tensor spectrum from conformal gravity
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- Quadratic Gravity
- Agravity up to infinite energy
- Metastability in Quadratic Gravity
- Inflationary Perturbations in No-Scale Theories
- On the gravitational seesaw in higher-derivative gravity
- Dimensional Transmutation in Gravity and Cosmology
- Predictions of quantum gravity in inflationary cosmology: effects of the Weyl-squared term
- Higher-order modified Starobinsky inflation
- Solving the Standard Model Problems in Softened Gravity
- Higher-order extension of Starobinsky inflation: initial conditions, slow-roll regime, and reheating phase
- Starobinsky inflation with a quadratic Weyl tensor
- Renormalization-group techniques for single-field inflation in primordial cosmology and quantum gravity
- Precision predictions of Starobinsky inflation with self-consistent Weyl-squared corrections
- Second-order corrections to Starobinsky inflation
- Modified Starobinsky inflation by the term
- Primordial Gravitational Waves in Quadratic Gravity
- Purely Virtual Particles in Quantum Gravity, Inflationary Cosmology and Collider Physics
- Strict renormalizability as a paradigm for fundamental physics
- Gauges for quadratic gravity: the extended transverse gauge and the energy-momentum tensor of the massive spin-2 field