907,720 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
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