Collapsing spherical stars in f(R) gravity
Abstract
We perform a careful investigation of the problem of physically realistic gravitational collapse of massive stars in f(R) gravity. We show that the extra matching conditions that arise in the modified gravity impose strong constraints on the stellar structure and thermodynamic properties. In our opinion these constraints are unphysical. We prove that no homogeneous stars with nonconstant Ricci scalar can be matched smoothly with a static exterior for any nonlinear function f(R). Therefore, these extra constraints make classes of physically realistic collapse scenarios in general relativity, nonadmissible in these theories. We also find an exact solution for an inhomogeneous collapsing star in the Starobinski model that obeys all the energy and matching conditions. However, we argue that such solutions are finetuned and unstable to matter perturbations. Possible consequences on black hole physics and the cosmic censorship conjecture are also discussed.
 Publication:

Physical Review D
 Pub Date:
 October 2014
 DOI:
 10.1103/PhysRevD.90.084011
 arXiv:
 arXiv:1409.2371
 Bibcode:
 2014PhRvD..90h4011G
 Keywords:

 04.20.Cv;
 04.20.Dw;
 Fundamental problems and general formalism;
 Singularities and cosmic censorship;
 General Relativity and Quantum Cosmology;
 High Energy Physics  Theory
 EPrint:
 11 pages, 8 figures, Revtex 4, Minor changes in text, Matches the accepted version in Physical Review D