Constraining Nonperturbative StrongField Effects in ScalarTensor Gravity by Combining Pulsar Timing and LaserInterferometer GravitationalWave Detectors
Abstract
Pulsar timing and laserinterferometer gravitationalwave (GW) detectors are superb laboratories to study gravity theories in the strongfield regime. Here, we combine these tools to test the monoscalartensor theory of Damour and EspositoFarèse (DEF), which predicts nonperturbative scalarization phenomena for neutron stars (NSs). First, applying Markovchain Monte Carlo techniques, we use the absence of dipolar radiation in the pulsartiming observations of five binary systems composed of a NS and a white dwarf, and eleven equations of state (EOSs) for NSs, to derive the most stringent constraints on the two free parameters of the DEF scalartensor theory. Since the binarypulsar bounds depend on the NS mass and the EOS, we find that current pulsartiming observations leave scalarization windows, i.e., regions of parameter space where scalarization can still be prominent. Then, we investigate if these scalarization windows could be closed and if pulsartiming constraints could be improved by laserinterferometer GW detectors, when spontaneous (or dynamical) scalarization sets in during the early (or late) stages of a binary NS (BNS) evolution. For the early inspiral of a BNS carrying constant scalar charge, we employ a Fishermatrix analysis to show that Advanced LIGO can improve pulsartiming constraints for some EOSs, and nextgeneration detectors, such as the Cosmic Explorer and Einstein Telescope, will be able to improve those bounds for all eleven EOSs. Using the late inspiral of a BNS, we estimate that for some of the EOSs under consideration, the onset of dynamical scalarization can happen early enough to improve the constraints on the DEF parameters obtained by combining the five binary pulsars. Thus, in the near future, the complementarity of pulsar timing and direct observations of GWs on the ground will be extremely valuable in probing gravity theories in the strongfield regime.
 Publication:

Physical Review X
 Pub Date:
 October 2017
 DOI:
 10.1103/PhysRevX.7.041025
 arXiv:
 arXiv:1704.07561
 Bibcode:
 2017PhRvX...7d1025S
 Keywords:

 General Relativity and Quantum Cosmology;
 Astrophysics  High Energy Astrophysical Phenomena;
 High Energy Physics  Phenomenology
 EPrint:
 19 pages, 11 figures