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Slowly rotating stars and black holes in dynamical Chern-Simons gravity

Haїmoud, Yacine-Ali and Chen, Yanbei (2011) Slowly rotating stars and black holes in dynamical Chern-Simons gravity. Physical Review D, 84 (12). Art. No. 124033. ISSN 2470-0010.

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Chern-Simons (CS) modified gravity is an extension to general relativity (GR) in which the metric is coupled to a scalar field, resulting in modified Einstein field equations. In the dynamical theory, the scalar field is itself sourced by the Pontryagin density of the space-time. In this paper, the coupled system of equations for the metric and the scalar field is solved numerically for slowly rotating neutron stars described with realistic equations of state and for slowly rotating black holes. An analytic solution for a constant-density nonrelativistic object is also presented. It is shown that the black hole solution cannot be used to describe the exterior space-time of a star as was previously assumed. In addition, whereas previous analysis were limited to the small-coupling regime, this paper considers arbitrarily large coupling strengths. It is found that the CS modification leads to two effects on the gravitomagnetic sector of the metric: (i) Near the surface of a star or the horizon of a black hole, the magnitude of the gravitomagnetic potential is decreased and frame-dragging effects are reduced in comparison to GR. (ii) In the case of a star, the angular momentum J, as measured by distant observers, is enhanced in CS gravity as compared to standard GR. For a large coupling strength, the near-zone frame-dragging effects become significantly screened, whereas the far-zone enhancements saturate at a maximum value ΔJ_(max)∼(M/R)J_(GR). Using measurements of frame-dragging effects around the Earth by Gravity Probe B and the LAGEOS satellites, a weak but robust constraint is set to the characteristic CS length scale, ξ^(1/4)≲10^8  km.

Item Type:Article
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Chen, Yanbei0000-0002-9730-9463
Additional Information:© 2011 American Physical Society. Received 29 October 2011; published 14 December 2011. We would like to thank Evan O’Connor for kindly providing tabulated solutions to the relativistic stellar structure equations for several neutron star masses and EOSs. We also thank Chris Hirata, Dan Grin, Nico Yunes, Frans Pretorius, Tristan Smith, Adrienne Erickcek, and Marc Kamionkowski for useful conversations on Chern-Simons gravity, and Sterl Phinney for helpful discussions on spin-orbit coupling. Y. A.-H. was supported by the U.S. Department of Energy (DE-FG03-92-ER40701) and the National Science Foundation (AST-0807337) while at Caltech and is currently supported by the NSF Grant No. AST-0807444. Y.C. is supported by NSF Grant Nos. PHY-0653653 and PHY-0601459, CAREER Grant No. PHY-0956189, and the David and Barbara Groce start-up fund at Caltech.
Funding AgencyGrant Number
Department of Energy (DOE)DE-FG03-92-ER40701
Caltech David and Barbara Groce Startup FundUNSPECIFIED
Issue or Number:12
Classification Code:PACS: 04.50.Kd, 04.80.Cc
Record Number:CaltechAUTHORS:20120125-151720239
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Official Citation:Slowly rotating stars and black holes in dynamical Chern-Simons gravity Yacine Ali-Haïmoud and Yanbei Chen Published 14 December 2011 (14 pages) 124033
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:28974
Deposited By: Ruth Sustaita
Deposited On:25 Jan 2012 23:38
Last Modified:09 Mar 2020 13:18

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