Massradius relation for neutron stars in f (R )=R +α R^{2} gravity: A comparison between purely metric and torsion formulations
Abstract
Within the framework of f (R )=R +α R^{2} gravity, we study realistic models of neutron stars, using equations of state compatible with the LIGO constraints, i.e., APR4, MPA1, SLy, and WW1. By numerically solving modified TolmanOppenheimerVolkoff equations, we investigate the massradius relation in both metric and torsional f (R )=R +α R^{2} gravity models. In particular, we observe that torsion effects decrease the compactness and total mass of neutron star with respect to the general relativity predictions, therefore mimicking the effects of a repulsive massive field. The opposite occurs in the metric theory, where mass and compactness increase with α , thus inducing an excess of mass that overtakes the standard general relativity limit. We also find that the sign of α must be reversed whether one considers the metric theory (positive) or torsion (negative) to avoid blowing up solutions. This could draw an easy test to either confirm or discard one or the other theory by determining the sign of parameter α .
 Publication:

Physical Review D
 Pub Date:
 February 2020
 DOI:
 10.1103/PhysRevD.101.044037
 arXiv:
 arXiv:1909.08847
 Bibcode:
 2020PhRvD.101d4037F
 Keywords:

 Astrophysics  High Energy Astrophysical Phenomena;
 General Relativity and Quantum Cosmology;
 High Energy Physics  Theory
 EPrint:
 16 pages, accepted for publication in Phys. Rev. D