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#### Constraining nonperturbative strong-field effects in scalar-tensor gravity by combining pulsar timing and laser-interferometer gravitational-wave detectors

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##### Fulltext (public)

1704.07561.pdf

(Preprint), 822KB

##### Supplementary Material (public)

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##### Citation

Shao, L., Sennett, N., Buonanno, A., Kramer, M., & Wex, N. (submitted). Constraining nonperturbative strong-field effects in scalar-tensor gravity by combining pulsar timing and laser-interferometer gravitational-wave detectors.

Cite as: http://hdl.handle.net/11858/00-001M-0000-002D-55D2-4

##### Abstract

Pulsar timing and laser-interferometer gravitational-wave (GW) detectors are
superb laboratories to study gravity theories in the strong-field regime. Here
we combine those tools to test the mono-scalar-tensor theory of Damour and
Esposito-Far\`ese (DEF), which predicts nonperturbative scalarization phenomena
for neutron stars (NSs). First, applying Markov-chain Monte Carlo techniques,
we use the absence of dipolar radiation in the pulsar-timing observations of
five binary systems composed of a NS and a white dwarf, and eleven equations of
state (EOS) for NSs, to derive the most stringent constraints on the two free
parameters of the DEF scalar-tensor theory. Since the binary-pulsar bounds
depend on the NS mass and the EOS, we find that current pulsar-timing
observations leave "scalarization mass gaps". Then, we investigate if these
scalarization mass gaps could be closed and if pulsar-timing constraints could
be improved by laser-interferometer 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 Fisher matrix analysis to show that Advanced LIGO can
improve pulsar-timing constraints for some EOSs, and next-generation 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
strong-field regime.