Constraints on perturbative f(R) gravity via neutron stars
Abstract
We study the structure of neutron stars in perturbative f(R) gravity models with realistic equations of state. We obtain massradius relations in a gravity model of the form f(R) = R+αR^{2}. We find that deviations from the results of general relativity, comparable to the variations due to using different equations of state (EoS'), are induced for α ~ 10^{9} cm^{2}. Some of the soft EoS' that are excluded within the framework of general relativity can be reconciled with the 2 solar mass neutron star recently observed for certain values of α within this range. For some of the EoS' we find that a new solution branch, which allows highly massive neutron stars, exists for values of α greater than a few 10^{9} cm^{2}. We find constraints on α for a variety of EoS' using the recent observational constraints on the massradius relation. These are all 5 orders of magnitude smaller than the recent constraint obtained via Gravity Probe B for this gravity model. The associated length scale \sqrt{alpha} approx 10^{5} cm is only an order of magnitude smaller than the typical radius of a neutron star, the probe used in this test. This implies that real deviations from general relativity can be even smaller.
 Publication:

Journal of Cosmology and Astroparticle Physics
 Pub Date:
 July 2011
 DOI:
 10.1088/14757516/2011/07/020
 arXiv:
 arXiv:1003.3179
 Bibcode:
 2011JCAP...07..020A
 Keywords:

 General Relativity and Quantum Cosmology;
 Astrophysics  High Energy Astrophysical Phenomena
 EPrint:
 18+1 pages, 7 figures