41 research outputs found
Measuring the ringdown scalar polarization of gravitational waves in Einstein scalar Gauss-Bonnet gravity
We model the scalar waves produced during the ringdown stage of binary black
hole coalescence in Einstein scalar Gauss-Bonnet (EsGB) gravity, using
numerical relativity simulations of the theory in the decoupling limit. Through
a conformal coupling of the scalar field to the metric in the matter-field
action, we show that the gravitational waves in this theory can have a scalar
polarization. We model the scalar quasi-normal modes of the ringdown signal in
EsGB gravity, and quantify the extent to which current and future gravitational
wave detectors could observe the spectrum of scalar radiation emitted during
the ringdown phase of binary black hole coalescence. We find that within the
limits of the theory's coupling parameters set by current theoretical and
observational constraints, the scalar ringdown signal from black hole remnants
in the mass range is expected to be well below the
detectability threshold with the current network of gravitational-wave
detectors (LIGO-Virgo-KAGRA), but is potentially measurable with
next-generation detectors such as the Einstein Telescope.Comment: 27 pages, 19 figures, to match published version in Phys. Rev.
Inverse-chirp signals and spontaneous scalarisation with self-interacting potentials in stellar collapse
We study how the gravitational wave signal from stellar collapse in scalar-tensor gravity varies under the influence of scalar self-interaction. To this end, we extract the gravitational radiation from numerical simulations of stellar collapse for a range of potentials with higher-order terms in addition to the quadratic mass term. Our study includes collapse to neutron stars and black holes and we find the strong inverse-chirp signals obtained for the purely quadratic potential to be exceptionally robust under changes in the potential at higher orders; quartic and sextic terms in the potential lead to noticeable differences in the wave signal only if their contribution is amplified, implying a relative fine-tuning to within 5 or more orders of magnitude between the mass and self-interaction parameters.This work was supported by the European Union’s H2020 ERC Consolidator Grant “Matter and strong-field gravity: New frontiers in Einstein’s theory” grant agreement no. MaGRaTh–646597 funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 690904, the COST Action Grant No. CA16104, from STFC Consolidator Grant No. ST/P000673/1, the SDSC Comet and TACC Stampede2 clusters through NSFXSEDE Award Nos. PHY-090003, and Cambridge’s CSD3 system system through STFC capital grants ST/P002307/1 and ST/R002452/1, STFC operations grant ST/R00689X/1 and DiRAC Allocation ACTP186. R.R.-M. acknowledges support by a STFC studentship
Stochastic gravitational wave background from supernovae in massive scalar-tensor gravity
In massive scalar-tensor gravity, core-collapse supernovae are strong sources
of scalar-polarized gravitational waves. These can be detectable out to large
distance. The dispersive nature of the propagation of waves in the massive
scalar field mean the gravitational wave signals are long lived and many such
signals can overlap to form a stochastic background. Using different models for
the population of supernova events in the nearby universe, we compute
predictions for the energy-density in the stochastic scalar-polarized
gravitational wave background from core-collapse events in massive
scalar-tensor gravity for theory parameters that facilitate strong
scalarization. The resulting energy density is below the current constraints on
a Gaussian stochastic gravitational wave background but large enough to be
detectable with the current generation of detectors when they reach design
sensitivity, indicating that it will soon be possible to place new constraints
on the parameter space of massive scalar-tensor gravity.Comment: to match published version in Phys.Rev.
TIGER: A data analysis pipeline for testing the strong-field dynamics of general relativity with gravitational wave signals from coalescing compact binaries
The direct detection of gravitational waves with upcoming second-generation
gravitational wave detectors such as Advanced LIGO and Virgo will allow us to
probe the genuinely strong-field dynamics of general relativity (GR) for the
first time. We present a data analysis pipeline called TIGER (Test
Infrastructure for GEneral Relativity), which is designed to utilize detections
of compact binary coalescences to test GR in this regime. TIGER is a
model-independent test of GR itself, in that it is not necessary to compare
with any specific alternative theory. It performs Bayesian inference on two
hypotheses: the GR hypothesis , and , which states that one or more of the post-Newtonian coefficients in
the waveform are not as predicted by GR. By the use of multiple sub-hypotheses
of , in each of which a different number of
parameterized deformations of the GR phase are allowed, an arbitrarily large
number of 'testing parameters' can be used without having to worry about a
model being insufficiently parsimonious if the true number of extra parameters
is in fact small. TIGER is well-suited to the regime where most sources have
low signal-to-noise ratios, again through the use of these sub-hypotheses.
Information from multiple sources can trivially be combined, leading to a
stronger test. We focus on binary neutron star coalescences, for which
sufficiently accurate waveform models are available that can be generated fast
enough on a computer to be fit for use in Bayesian inference. We show that the
pipeline is robust against a number of fundamental, astrophysical, and
instrumental effects, such as differences between waveform approximants, a
limited number of post-Newtonian phase contributions being known, the effects
of neutron star spins and tidal deformability on the orbital motion, and
instrumental calibration errors.Comment: 12 pages, 9 figures. Version as appears in Phys. Rev.
Structure of Neutron Stars in Massive Scalar-Tensor Gravity
We compute families of spherically symmetric neutron-star models in two-derivative scalar-tensor theories of gravity with a massive scalar field. The numerical approach we present allows us to compute the resulting spacetimes out to infinite radius using a relaxation algorithm on a compactified grid. We discuss the structure of the weakly and strongly scalarized branches of neutron-star models thus obtained and their dependence on the linear and quadratic coupling parameters α0, β0 between the scalar and tensor sectors of the theory, as well as the scalar mass μ. For highly negative values of β0, we encounter configurations resembling a “gravitational atom”, consisting of a highly compact baryon star surrounded by a scalar cloud. A stability analysis based on binding-energy calculations suggests that these configurations are unstable and we expect them to migrate to models with radially decreasing baryon density and scalar field strength
Long-Lived Inverse Chirp Signals from Core-Collapse in Massive Scalar-Tensor Gravity.
This Letter considers stellar core collapse in massive scalar-tensor theories of gravity. The presence of a mass term for the scalar field allows for dramatic increases in the radiated gravitational wave signal. There are several potential smoking gun signatures of a departure from general relativity associated with this process. These signatures could show up within existing LIGO-Virgo searches