Spherically Symmetric Solutions in F(R) Gravity and Gravitational Repulsion

Abstract

Spherically symmetric solutions in F(R) theories in astronomical systems with rising energy density are studied. The range of parameters is established for which the flat space-time approximation for the background metric is valid. For the solutions in which the curvature scalar oscillates with large amplitude and high frequency, found in our previous papers, it is shown that the analysis of the Jeans instability is strongly modified. It is discovered that for large astronomical objects modified gravity can be repulsive, so such objects shrink forming relatively thin shells instead of quasi uniform bodies. This may explain the formation of cosmic voids.

6 pages. References are added

References in corpus (7)

• Unified cosmic history in modified gravity: from F(R) theory to Lorentz non-invariant models
• Models of f(R) Cosmic Acceleration that Evade Solar-System Tests
• Disappearing cosmological constant in f(R) gravity
• Hydrostatic equilibrium and stellar structure in f(R)-gravity
• The Newtonian Limit of F(R) gravity
• A Singularity Problem with f(R) Dark Energy
• Particle Production in f(R) Gravity during Structure Formation

Cited by in corpus (8)

• Jeans Instability in Classical and Modified Gravity
• Dynamical Instability of Spherical Anisotropic Sources in $f(R,T,R_{\mu \nu }{T}^{\mu \nu })$ Gravity
• Jupiter and jovian (exo)-planets in Palatini $f(\bar{R})$ gravity
• Cosmological acceleration
• Perturbative solutions of the $f(R)$-theory of gravity in a central gravitational field and some applications
• Gravitational instability in oscillating background
• Gravitational Collapse in Repulsive $R+{\mu }^4/R$ Gravity
• Nonstatic Reissner-Nordström metric in the perturbative $f(R)$ theory: Embedding in the background of the FLRW cosmology, uniqueness of solutions, the TOV equation