Isolated and binary neutron stars in dynamical ChernSimons gravity
Abstract
We study isolated and binary neutron stars in dynamical ChernSimons gravity. This theory modifies the EinsteinHilbert action through the introduction of a dynamical scalar field coupled to the Pontryagin density. We here treat this theory as an effective model, working to leading order in the ChernSimons coupling. We first construct isolated neutron star solutions in the slowrotation expansion to quadratic order in spin. We find that isolated neutron stars acquire a scalar dipole charge that corrects its spin angular momentum to linear order in spin and corrects its mass and quadrupole moment to quadratic order in spin, as measured by an observer at spatial infinity. We then consider neutron stars binaries that are widely separated and solve for their orbital evolution in this modified theory. We find that the evolution of postKeplerian parameters is modified, with the rate of periastron advance being the dominant correction at first postNewtonian order. We conclude by applying these results to observed pulsars with the aim to place constraints on dynamical ChernSimons gravity. We find that the modifications to the observed mass are degenerate with the neutron star equation of state, which prevents us from testing the theory with the inferred mass of the millisecond pulsar J16142230. We also find that the corrections to the postKeplerian parameters are too small to be observable today even with data from the double binary pulsar J07373039. Our results suggest that pulsar observations are not currently capable of constraining dynamical ChernSimons gravity, and thus, gravitationalwave observations may be the only path to a stringent constraint of this theory in the imminent future.
 Publication:

Physical Review D
 Pub Date:
 April 2013
 DOI:
 10.1103/PhysRevD.87.084058
 arXiv:
 arXiv:1302.1918
 Bibcode:
 2013PhRvD..87h4058Y
 Keywords:

 04.30.w;
 04.50.Kd;
 04.80.Cc;
 97.60.Jd;
 Gravitational waves: theory;
 Modified theories of gravity;
 Experimental tests of gravitational theories;
 Neutron stars;
 General Relativity and Quantum Cosmology;
 Astrophysics  High Energy Astrophysical Phenomena
 EPrint:
 28 pages, 7 figures, 3 tables