scholarly journals Gravitational wave astronomy: needle in a haystack

2013 ◽  
Vol 371 (1984) ◽  
pp. 20110540 ◽  
Author(s):  
Neil J Cornish
Keyword(s):  
Gravitational Wave ◽  
Strong Field ◽  
Direct Detection ◽  
Dynamical Regime ◽  
New Era ◽  
Pulsar Timing ◽  
Astrophysical Objects ◽  
Model Spaces ◽  
Instrument Noise ◽  
Non Gaussian

A worldwide array of highly sensitive ground-based interferometers stands poised to usher in a new era in astronomy with the first direct detection of gravitational waves. The data from these instruments will provide a unique perspective on extreme astrophysical objects, such as neutron stars and black holes, and will allow us to test Einstein’s theory of gravity in the strong field, dynamical regime. To fully realize these goals, we need to solve some challenging problems in signal processing and inference, such as finding rare and weak signals that are buried in non-stationary and non-Gaussian instrument noise, dealing with high-dimensional model spaces, and locating what are often extremely tight concentrations of posterior mass within the prior volume. Gravitational wave detection using space-based detectors and pulsar timing arrays bring with them the additional challenge of having to isolate individual signals that overlap one another in both time and frequency. Promising solutions to these problems will be discussed, along with some of the challenges that remain.

scholarly journals Probing dark matter clumps, strings and domain walls with gravitational wave detectors

2021 ◽  
Vol 81 (9) ◽  
Author(s):  
Joerg Jaeckel ◽  
Sebastian Schenk ◽  
Michael Spannowsky
Keyword(s):  
Dark Matter ◽  
Gravitational Wave ◽  
Domain Walls ◽  
Matter Power Spectrum ◽  
Pulsar Timing ◽  
Astrophysical Objects ◽  
Gravitational Wave Interferometer ◽  
Moderate Sensitivity ◽  
Gravitational Pull ◽  
Square Kilometer Array

AbstractGravitational wave astronomy has recently emerged as a new way to study our Universe. In this work, we survey the potential of gravitational wave interferometers to detect macroscopic astrophysical objects comprising the dark matter. Starting from the well-known case of clumps we expand to cosmic strings and domain walls. We also consider the sensitivity to measure the dark matter power spectrum on small scales. Our analysis is based on the fact that these objects, when traversing the vicinity of the detector, will exert a gravitational pull on each node of the interferometer, in turn leading to a differential acceleration and corresponding Doppler signal, that can be measured. As a prototypical example of a gravitational wave interferometer, we consider signals induced at LISA. We further extrapolate our results to gravitational wave experiments sensitive in other frequency bands, including ground-based interferometers, such as LIGO, and pulsar timing arrays, e.g. ones based on the Square Kilometer Array. Assuming moderate sensitivity improvements beyond the current designs, clumps, strings and domain walls may be within reach of these experiments.

scholarly journals Constraining the nanohertz gravitational wave background with the Parkes Pulsar Timing Array

2012 ◽  
Vol 8 (S291) ◽  
pp. 177-177
Author(s):  
Ryan Shannon
Keyword(s):  
Gravitational Wave ◽  
Gravitational Waves ◽  
Direct Detection ◽  
Massive Black Hole ◽  
Black Hole Binaries ◽  
Pulsar Timing ◽  
The Galaxy ◽  
Gravitational Wave Background ◽  
Pulsar Timing Array ◽  
The Universe

AbstractThe direct detection of gravitational waves will usher in a new era of astrophysics, enabling the study of regions of the universe opaque to electromagnetic radiation or electromagnetically quiet. An ensemble of pulsars (referred to as a pulsar timing array) provides a set of clocks distributed across the Galaxy sensitive to gravitational waves with periods on the order of five years (frequencies of many nanohertz). Plausible source of gravitational waves in this frequency band include massive black hole binaries in the throes of mergers and oscillating cosmic strings. The stochastic gravitational wave background, the sum of gravitational waves emitted throughout the universe, is the most likely signal to be detected by a pulsar timing array.While the detection of gravitational waves will be a milestone in pulsar astronomy, a constraining limit on the strength of the gravitational wave background can be used to constrain cosmological models and early Universe physics. Here we present a new algorithm that can be used to constrain the strength of the GWB with a pulsar timing array. We then apply this technique to Parkes Pulsar Timing Array observations and place a new limit on the strength of the GWB. We conclude by discussing the astrophysical implications of this limit and the prospects for detecting gravitational waves with pulsars.

scholarly journals Pulsars as probes of gravity and fundamental physics

2016 ◽  
Vol 25 (14) ◽  
pp. 1630029 ◽  
Author(s):  
Michael Kramer
Keyword(s):  
Strong Field ◽  
Direct Detection ◽  
Field Tests ◽  
Dense Matter ◽  
Experimental Tests ◽  
Fundamental Physics ◽  
Tests Of General Relativity ◽  
Pulsar Timing ◽  
Wide Range ◽  
Tests Of Gravity

Radio-loud neutron stars known as pulsars allow a wide range of experimental tests for fundamental physics, ranging from the study of super-dense matter to tests of General Relativity (GR) and its alternatives. As a result, pulsars provide strong-field tests of gravity, they allow for the direct detection of gravitational waves in a “pulsar timing array” (PTA), and they promise the future study of black hole properties. This contribution gives an overview of the on-going experiments and recent results.

scholarly journals Gravitational Wave Polarizations in f (R) Gravity and Scalar-Tensor Theory

2018 ◽  
Vol 168 ◽  
pp. 01003 ◽  
Author(s):  
Yungui Gong ◽  
Shaoqi Hou
Keyword(s):  
Gravitational Wave ◽  
Gravitational Waves ◽  
Alternative Theories Of Gravity ◽  
Longitudinal Polarization ◽  
New Era ◽  
Tensor Theory ◽  
Pulsar Timing ◽  
Theories Of Gravity ◽  
Pulsar Timing Array ◽  
Scalar Mode

The detection of gravitational waves by the Laser Interferometer Gravitational-Wave Observatory opens a new era to use gravitational waves to test alternative theories of gravity. We investigate the polarizations of gravitational waves in f (R) gravity and Horndeski theory, both containing scalar modes. These theories predict that in addition to the familiar + and × polarizations, there are transverse breathing and longitudinal polarizations excited by the massive scalar mode and the new polarization is a single mixed state. It would be very difficult to detect the longitudinal polarization by interferometers, while pulsar timing array may be the better tool to detect the longitudinal polarization.

scholarly journals Gravitational-Wave Detection Using Pulsars: Status of the Parkes Pulsar Timing Array Project

2009 ◽  
Vol 26 (2) ◽  
pp. 103-109 ◽  
Author(s):  
G. B. Hobbs ◽  
M. Bailes ◽  
N. D. R. Bhat ◽  
S. Burke-Spolaor ◽  
D. J. Champion ◽  
...  
Keyword(s):  
Gravitational Wave ◽  
Gravitational Waves ◽  
Direct Detection ◽  
Low Frequency ◽  
Current Status ◽  
Binary Black Holes ◽  
Gravitational Wave Detection ◽  
Wave Detection ◽  
Pulsar Timing ◽  
Pulsar Timing Array

AbstractThe first direct detection of gravitational waves may be made through observations of pulsars. The principal aim of pulsar timing-array projects being carried out worldwide is to detect ultra-low frequency gravitational waves (f ∼ 10−9–10−8 Hz). Such waves are expected to be caused by coalescing supermassive binary black holes in the cores of merged galaxies. It is also possible that a detectable signal could have been produced in the inflationary era or by cosmic strings. In this paper, we review the current status of the Parkes Pulsar Timing Array project (the only such project in the Southern hemisphere) and compare the pulsar timing technique with other forms of gravitational-wave detection such as ground- and space-based interferometer systems.

scholarly journals The Polarizations of Gravitational Waves

Universe ◽  
2018 ◽  
Vol 4 (8) ◽  
pp. 85 ◽  
Author(s):  
Yungui Gong ◽  
Shaoqi Hou
Keyword(s):  
General Relativity ◽  
Gravitational Wave ◽  
Gravitational Waves ◽  
High Speed ◽  
Strong Field ◽  
Alternative Theories Of Gravity ◽  
Pulsar Timing ◽  
Theories Of Gravity ◽  
Alternative Theories

The gravitational wave provides a new method to examine General Relativity and its alternatives in the high speed, strong field regime. Alternative theories of gravity generally predict more polarizations than General Relativity, so it is important to study the polarization contents of theories of gravity to reveal the nature of gravity. In this talk, we analyze the polarization contents of Horndeski theory and f(R) gravity. We find out that in addition to the familiar plus and cross polarizations, a massless Horndeski theory predicts an extra transverse polarization, and there is a mix of pure longitudinal and transverse breathing polarizations in the massive Horndeski theory and f(R) gravity. It is possible to use pulsar timing arrays to detect the extra polarizations in these theories. We also point out that the classification of polarizations using Newman–Penrose variables cannot be applied to massive modes. It cannot be used to classify polarizations in Einstein-æther theory or generalized Tensor-Vector-Scalar (TeVeS) theory, either.

scholarly journals Forecast constraints on cosmic strings from future CMB, pulsar timing, and gravitational wave direct detection experiments

2013 ◽  
Vol 87 (2) ◽  
Author(s):  
Sachiko Kuroyanagi ◽  
Koichi Miyamoto ◽  
Toyokazu Sekiguchi ◽  
Keitaro Takahashi ◽  
Joseph Silk
Keyword(s):  
Gravitational Wave ◽  
Direct Detection ◽  
Cosmic Strings ◽  
Pulsar Timing

scholarly journals The scalar chemical potential in cosmological collider physics

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Arushi Bodas ◽  
Soubhik Kumar ◽  
Raman Sundrum
Keyword(s):  
Particle Production ◽  
Chemical Potential ◽  
Direct Detection ◽  
Heavy Particle ◽  
Scalar Particle ◽  
Energy Scale ◽  
Fine Tuning ◽  
Tree Level ◽  
Heavy Particles ◽  
Non Gaussian

Abstract Non-analyticity in co-moving momenta within the non-Gaussian bispectrum is a distinctive sign of on-shell particle production during inflation, presenting a unique opportunity for the “direct detection” of particles with masses as large as the inflationary Hubble scale (H). However, the strength of such non-analyticity ordinarily drops exponentially by a Boltzmann-like factor as masses exceed H. In this paper, we study an exception provided by a dimension-5 derivative coupling of the inflaton to heavy-particle currents, applying it specifically to the case of two real scalars. The operator has a “chemical potential” form, which harnesses the large kinetic energy scale of the inflaton, $$ {\overset{\cdot }{\phi}}_0^{1/2}\approx 60H $$ ϕ ⋅ 0 1 / 2 ≈ 60 H , to act as an efficient source of scalar particle production. Derivative couplings of inflaton ensure radiative stability of the slow-roll potential, which in turn maintains (approximate) scale-invariance of the inflationary correlations. We show that a signal not suffering Boltzmann suppression can be obtained in the bispectrum with strength fNL ∼ $$ \mathcal{O} $$ O (0.01–10) for an extended range of scalar masses $$ \lesssim {\overset{\cdot }{\phi}}_0^{1/2} $$ ≲ ϕ ⋅ 0 1 / 2 , potentially as high as 1015 GeV, within the sensitivity of upcoming LSS and more futuristic 21-cm experiments. The mechanism does not invoke any particular fine-tuning of parameters or breakdown of perturbation-theoretic control. The leading contribution appears at tree-level, which makes the calculation analytically tractable and removes the loop-suppression as compared to earlier chemical potential studies of non-zero spins. The steady particle production allows us to infer the effective mass of the heavy particles and the chemical potential from the variation in bispectrum oscillations as a function of co-moving momenta. Our analysis sets the stage for generalization to heavy bosons with non-zero spin.

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