Vacuum structure for scalar cosmological perturbations in Modified Gravity Models

Abstract

We have found for the general class of Modified Gravity Models f(R,G) a new instability which can arise in vacuum for the scalar modes of the cosmological perturbations if the background is not de Sitter. In particular, the short-wavelength modes, if stable, in general have a group velocity which depends linearly in k, the wave number. Therefore these modes will be in general superluminal. We have also discussed the condition for which in general these scalar modes will be ghost-like. There is a subclass of these models, defined out of properties of the function f(R,G) and to which the f(R) and f(G) models belong, which however does not have this feature.

17 pages, 1 figure, uses RevTeX, references added

References in corpus (64)

• Is Cosmic Speed-Up Due to New Gravitational Physics?
• Modified gravity with negative and positive powers of the curvature: unification of the inflation and of the cosmic acceleration
• Curvature Quintessence
• Modified Gauss-Bonnet theory as gravitational alternative for dark energy
• Perturbations in k-inflation
• Modified f(R) gravity consistent with realistic cosmology: from matter dominated epoch to dark energy universe
• Class of viable modified $f(R)$ gravities describing inflation and the onset of accelerated expansion
• Ghost Condensation and a Consistent Infrared Modification of Gravity
• Dark energy in modified Gauss-Bonnet gravity: late-time acceleration and the hierarchy problem
• Cosmological viability of f(R)-gravity as an ideal fluid and its compatibility with a matter dominated phase
• Gauss-Bonnet dark energy
• Conditions for the cosmological viability of f(R) dark energy models
• The phantom menaced: constraints on low-energy effective ghosts
• The Cosmology of Generalized Modified Gravity Models
• Are f(R) dark energy models cosmologically viable ?
• Avoiding Dark Energy with 1/R Modifications of Gravity
• The Large Scale Structure of f(R) Gravity
• k-Essence, superluminal propagation, causality and emergent geometry
• Singularity-free cosmological solutions of the superstring effective action
• Dark energy cosmology from higher-order, string-inspired gravity and its reconstruction
• Post-Newtonian constraints on f(R) cosmologies in metric formalism
• Post-Newtonian constraints on f(R) cosmologies in Palatini formalism
• Extended Gravity Theories and the Einstein-Hilbert Action
• Construction of cosmologically viable f(G) gravity models
• The pattern of growth in viable f(R) cosmologies
• The Cosmology of Modified Gauss-Bonnet Gravity
• Dynamics of Linear Perturbations in f(R) Gravity
• Inconsistency of interacting, multi-graviton theories
• Classical evolution and quantum generation in generalized gravity theories including string corrections and tachyon: Unified analyses
• Cosmology and Astrophysical Constraints of Gauss-Bonnet Dark Energy
• Stability of Cosmological Solution in f(R) Models of Gravity
• Gauss-Bonnet Quintessence: Background Evolution, Large Scale Structure and Cosmological Constraints
• The fate of (phantom) dark energy universe with string curvature corrections
• Instability of 1-loop superstring cosmology
• f(R) cosmology by Noether's symmetry
• Spontaneous breaking of Lorentz invariance, black holes and perpetuum mobile of the 2nd kind
• Dark energy from modified F(R)-scalar-Gauss-Bonnet gravity
• Ghosts, Instabilities, and Superluminal Propagation in Modified Gravity Models
• Modified-Source Gravity and Cosmological Structure Formation
• On causality and superluminal behavior in classical field theories. Applications to k-essence theories and MOND-like theories of gravity
• Generalized Gravity and a Ghost
• One-Loop Superstring Cosmology and the Non-Singular Universe
• Evolution of cosmological perturbations in non-singular string cosmologies
• Ghost conditions for Gauss-Bonnet cosmologies
• Second Order Scalar Invariants of the Riemann Tensor: Applications to Black Hole Spacetimes
• Constraining Inverse Curvature Gravity with Supernovae
• No-go theorem for k-essence dark energy
• Causality and the speed of sound
• f(R)-Brane
• Non-Trivial Vacua in Higher-Derivative Gravitation
• Ghost Constraints on Modified Gravity
• Escaping from the black hole?
• Nonlinear growth in modified gravity theories of dark energy
• On the Newtonian limit of Generalized Modified Gravity Models
• Consistent long distance modification of gravity from inverse powers of the curvature
• Attractor scenarios and superluminal signals in k-essence cosmology
• Conserved cosmological structures in the one-loop superstring effective action
• Perturbative aspects and conformal solutions of F(R) gravity
• Traveling Faster than the Speed of Light in Non-Commutative Geometry
• Unsuccessful cosmology with Modified Gravity Models
• Four-Dimensional Higher-Derivative Supergravity and Spontaneous Supersymmetry Breaking
• A Note on the Viability of Gauss-Bonnet Cosmology
• Liouville-like solutions in dilaton gravity with Gauss-Bonnet modifications
• Massive gravitons trapped inside a hypermonopole

Cited by in corpus (63)

• f(R) theories
• Finite-time future singularities in modified Gauss-Bonnet and $\mathcal{F}(R,G)$ gravity and singularity avoidance
• Cosmology of a covariant Galileon field
• Cosmological inflation in $F(R,\mathcal{G})$ gravity
• Curing singularities in cosmological evolution of F(R) gravity
• Conditions for the cosmological viability of the most general scalar-tensor theories and their applications to extended Galileon dark energy models
• Generalized Galileon cosmology
• Singular Bouncing Cosmology from Gauss-Bonnet Modified Gravity
• Solar system constraints on f(G) gravity models
• Observational constraints on Galileon cosmology
• Energy conditions in modified Gauss-Bonnet gravity
• Matter perturbations in Galileon cosmology
• Stability of Schwarzschild-like solutions in f(R,G) gravity models
• Detailed balance in Horava-Lifshitz gravity
• Regular black holes in $f(T)$ Gravity through a nonlinear electrodynamics source
• A new perspective on Dark Energy modeling via Genetic Algorithms
• Some aspects of generalized modified gravity models
• Regular black holes in $f(R)$ gravity coupled to nonlinear electrodynamics
• Reconstruction and deceleration-acceleration transitions in modified gravity
• Ghost-free Gauss-Bonnet Theories of Gravity
• Charged Compact Stars in $f(\mathcal{G})$ Gravity
• Matter instabilities in general Gauss-Bonnet gravity
• Primordial perturbation with a modified dispersion relation
• Non-geodesic motion in $f(\mathcal{G})$ gravity with non-minimal coupling
• Cosmological perturbations of a perfect fluid and noncommutative variables
• Dynamical analysis on $f(R,\mathcal{G})$ cosmology
• Auxiliary fields representation for modified gravity models
• Observational constraints on Gauss-Bonnet cosmology
• Fab 5: Noncanonical Kinetic Gravity, Self Tuning, and Cosmic Acceleration
• Coincident f(Q) gravity: black holes, regular black holes and black bounces
• Cosmological perturbation in f(R,G) theories with a perfect fluid
• Stellar Structures in $f(\mathcal{G})$ Gravity with Tolman-Kuchowicz Spacetime
• Analysis of Charged Compact Stars in Modified Gravity
• Anisotropic stress and stability in modified gravity models
• Late-time constraints on modified Gauss-Bonnet cosmology
• On the superstring-inspired quantum correction to the Starobinsky model of inflation
• Born-Infeld and Charged Black Holes with non-linear source in $f(T)$ Gravity
• Tracing the cosmic history by Gauss-Bonnet gravity
• Exact Solutions in Higher-Dimensional Lovelock and $Ad{S}_5$ Chern-Simons Gravity
• Scalar mode propagation in modified gravity with a scalar field
• Spherical Accretion of Matter by Charged Black Holes on f(T) Gravity
• Cosmology in modified $f(\mathcal{G})$ gravity: a late time cosmic phenomena
• Bouncing cosmology in $f(R,\mathcal{G})$ gravity by order reduction
• Cosmological perturbations in f(G) gravity
• Perfect fluid in Lagrangian formulation due to generalized three-form field
• Note on the Gauss-Bonnet braneworld scenario
• Supernova, baryon acoustic oscillations, and CMB surface distance constraints on f(G) higher order gravity models
• Constraints on modified Gauss-Bonnet gravity during big bang nucleosynthesis
• Charged Compact Stars in Extended $f(\mathcal{R},\mathcal{G},\mathcal{T})$ Gravity
• Bounds from ISW-galaxy cross-correlations on generalized covariant Galileon models
• Multi-horizons black hole solutions, photon sphere and perihelion shift in weak ghost-free Gauss-Bonnet theory of gravity
• Energy Conditions in Gauss-Bonnet Gravity
• Generalized Teleparallel Theory
• Stability of Poincaré gauge theory with cubic order invariants
• Motion of pole-dipole and quadrupole particles in non-minimally coupled theories of gravity
• Inflationary Cosmology via Quantum Corrections in M-theory
• Purely metric Horndeski theories and spontaneous curvaturization of black holes
• The scalar-torsion gravity corrections in the first-order inflationary models
• Black holes in $f(R)$ gravity coupled to nonlinear electromagnetic fields
• Removing Ostrogradski's ghost from cosmological perturbations in $f(R,R_{\mu \nu }^2,C_{\mu \nu \rho \sigma }^2)$ gravity
• Primordial perturbations and inflation in a holography inspired Gauss-Bonnet cosmology
• Friedmann's Universe Controlled by Gauss-Bonnet Modified Gravity
• $f(R,\mathcal{G})$-cosmological dynamics in the FLRW background