82 research outputs found
Measuring stochastic gravitational-wave energy beyond general relativity
Gravity theories beyond general relativity (GR) can change the properties of
gravitational waves: their polarizations, dispersion, speed, and, importantly,
energy content are all heavily theory- dependent. All these corrections can
potentially be probed by measuring the stochastic gravitational- wave
background. However, most existing treatments of this background beyond GR
overlook modifications to the energy carried by gravitational waves, or rely on
GR assumptions that are invalid in other theories. This may lead to
mistranslation between the observable cross-correlation of detector outputs and
gravitational-wave energy density, and thus to errors when deriving
observational constraints on theories. In this article, we lay out a generic
formalism for stochastic gravitational- wave searches, applicable to a large
family of theories beyond GR. We explicitly state the (often tacit) assumptions
that go into these searches, evaluating their generic applicability, or lack
thereof. Examples of problematic assumptions are: statistical independence of
linear polarization amplitudes; which polarizations satisfy equipartition; and
which polarizations have well-defined phase velocities. We also show how to
correctly infer the value of the stochastic energy density in the context of
any given theory. We demonstrate with specific theories in which some of the
traditional assumptions break down: Chern-Simons gravity, scalar-tensor theory,
and Fierz-Pauli massive gravity. In each theory, we show how to properly
include the beyond-GR corrections, and how to interpret observational results.Comment: 18 pages (plus appendices), 1 figur
Probing gravitational wave polarizations with signals from compact binary coalescences
In this technical note, we study the possibility of using networks of
ground-based detectors to directly measure gravitational-wave polarizations
using signals from compact binary coalescences. We present a simple data
analysis method to partially achieve this, assuming presence of a strong signal
well-captured by a GR template.Comment: Technical not
Extracting the Gravitational Recoil from Black Hole Merger Signals
Gravitational waves carry energy, angular momentum, and linear momentum. In generic binary black hole mergers, the loss of linear momentum imparts a recoil velocity, or a “kick,” to the remnant black hole. We exploit recent advances in gravitational waveform and remnant black hole modeling to extract information about the kick from the gravitational wave signal. Kick measurements such as these are astrophysically valuable, enabling independent constraints on the rate of second-generation merger. Further, we show that kicks must be factored into future ringdown tests of general relativity with third-generation gravitational wave detectors to avoid systematic biases. We find that, although little information can be gained about the kick for existing gravitational wave events, interesting measurements will soon become possible as detectors improve. We show that, once LIGO and Virgo reach their design sensitivities, we will reliably extract the kick velocity for generically precessing binaries—including the so-called superkicks, reaching up to 5000 km/s
Self-Completeness and the Generalized Uncertainty Principle
The generalized uncertainty principle discloses a self-complete
characteristic of gravity, namely the possibility of masking any curvature
singularity behind an event horizon as a result of matter compression at the
Planck scale. In this paper we extend the above reasoning in order to overcome
some current limitations to the framework, including the absence of a
consistent metric describing such Planck-scale black holes. We implement a
minimum-size black hole in terms of the extremal configuration of a neutral
non-rotating metric, which we derived by mimicking the effects of the
generalized uncertainty principle via a short scale modified version of
Einstein gravity. In such a way, we find a self-consistent scenario that
reconciles the self-complete character of gravity and the generalized
uncertainty principle.Comment: 20 pages, 6 figures, v2: additional references, version in press on
JHE
Modeling the Dispersion and Polarization Content of Gravitational Waves for Tests of General Relativity
We propose a generic, phenomenological approach to modifying the dispersion
of gravitational waves, independent of corrections to the generation mechanism.
This model-independent approach encapsulates all previously proposed
parametrizations, including Lorentz violation in the Standard-Model Extension,
and provides a roadmap for additional theories. Furthermore, we present a
general approach to include modulations to the gravitational-wave polarization
content. The framework developed here can be implemented in existing data
analysis pipelines for future gravitational-wave observation runs.Comment: 4 pages, Presented at the Seventh Meeting on CPT and Lorentz
Symmetry, Bloomington, Indiana, June 20-24, 201
Detecting Beyond-Einstein Polarizations of Continuous Gravitational Waves
The direct detection of gravitational waves with the next generation
detectors, like Advanced LIGO, provides the opportunity to measure deviations
from the predictions of General Relativity. One such departure would be the
existence of alternative polarizations. To measure these, we study a single
detector measurement of a continuous gravitational wave from a triaxial pulsar
source. We develop methods to detect signals of any polarization content and
distinguish between them in a model independent way. We present LIGO S5
sensitivity estimates for 115 pulsars.Comment: submitted to PR
Comment on "Analysis of Ringdown Overtones in GW150914''
Cotesta et al. (2022) reanalyze the GW150914 ringdown, arguing against the
presence of an overtone and suggesting claims of its detection in Isi et al.
(2019) were driven by noise. Here we point out a number of technical errors in
that analysis, including a software bug, and show that features highlighted as
problematic are in fact expected and encountered in simulated data. After
fixes, the code in used in Cotesta et al. (2022) produces results consistent
with the presence of the overtone. All code and data are available at
https://github.com/maxisi/gw150914_rd_commentComment: 2 pages, 2 figures; a reproducible article prepared with ShowYourWork
hosted at https://github.com/maxisi/gw150914_rd_commen
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