Stochastic backgrounds in alternative theories of gravity: Overlap reduction functions for pulsar timing arrays

Chamberlin, S. J.; Siemens, X.

doi:10.1103/physrevd.85.082001

Cited by 123 publications

(118 citation statements)

References 29 publications

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“…A second method to detect GWs is to use pulsar timing arrays (PTAs) [54][55][56][57][58][59][60]. The propagation of radial pulses emanating from pulsars is affected by the stochastic GW background.…”

Section: Experimental Testsmentioning

confidence: 99%

The Polarizations of Gravitational Waves

Gong

Hou

2018

Universe

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Abstract: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-aether theory or generalized Tensor-Vector-Scalar (TeVeS) theory, either.

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Section: Experimental Testsmentioning

confidence: 99%

The Polarizations of Gravitational Waves

Gong

Hou

2018

Universe

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“…Detecting a GWB, with amplitude and slope consistent with the expected signal generated by an ensemble of SBHBs, would prove the validity of the models that predict the existence of tight SBHBs, and, in a broader context, would support our current understanding of the formation and evolution of galaxies. Moreover, the detection of a GWB could put constraints on alternative theories of gravity, or prove their validity against General Relativity (Chamberlin & Siemens 2012). However, an ensemble of SBHBs could also produce a spectrum different than a simple power law (Sesana et al 2004;Kocsis & Sesana 2011;McWilliams et al 2014;Ravi et al 2014), and other GW sources could also lead to different measurable GWBs; detecting the actual shape of the GWB would help discriminate between these different models (Sampson et al 2015).…”

Section: Introductionmentioning

confidence: 99%

Expected properties of the first gravitational wave signal detected with pulsar timing arrays

Rosado

Sesana

Gair

2015

Monthly Notices of the Royal Astronomical Society

210

235

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In this paper we attempt to investigate the nature of the first gravitational wave (GW) signal to be detected by pulsar timing arrays (PTAs): will it be an individual, resolved supermassive black hole binary (SBHB), or a stochastic background made by the superposition of GWs produced by an ensemble of SBHBs? To address this issue, we analyse a broad set of simulations of the cosmological population of SBHBs, that cover the entire parameter space allowed by current electromagnetic observations in an unbiased way. For each simulation, we construct the expected GW signal and identify the loudest individual sources. We then employ appropriate detection statistics to evaluate the relative probability of detecting each type of source as a function of time for a variety of PTAs; we consider the current International PTA, and speculate into the era of the Square Kilometre Array. The main properties of the first detectable individual SBHBs are also investigated. Contrary to previous work, we cast our results in terms of the detection probability (DP), since the commonly adopted criterion based on a signal-to-noise ratio threshold is statistic-dependent and may result in misleading conclusions for the statistics adopted here. Our results confirm quantitatively that a stochastic signal is more likely to be detected first (with between 75 to 93 per cent probability, depending on the array), but the DP of single-sources is not negligible. Our framework is very flexible and can be easily extended to more realistic arrays and to signal models including environmental coupling and SBHB eccentricity.

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“…It is likely that the GW background would be less diluted when the source is projected, leading potentially to β ≈ 1. Thus, it may be easier for observatories to detect cosmological backgrounds in nonstandard theories of gravity [47].…”

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confidence: 99%

Estimates of maximum energy density of cosmological gravitational-wave backgrounds

Giblin

Thrane

2014

Phys. Rev. D

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The recent claim by BICEP2 of evidence for primordial gravitational waves has focused interest on the potential for early-Universe cosmology using gravitational waves. In addition to cosmic microwave background detectors, efforts are underway to carry out gravitational-wave astronomy with pulsar timing arrays, space-based detectors, and terrestrial detectors. These efforts will probe a wide range of times in the early Universe, during which backgrounds may have been produced through processes such as phase transitions or preheating. We derive a rule of thumb (not so strong as an upper limit) governing the maximum energy density of cosmological backgrounds. For most scenarios, we expect the energy density spectrum to peak at values of Ω gw ðfÞ ≲ 10 −12AE2 . We discuss the applicability of this rule and the implications for gravitational-wave astronomy.

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Stochastic backgrounds in alternative theories of gravity: Overlap reduction functions for pulsar timing arrays

Cited by 123 publications

References 29 publications

The Polarizations of Gravitational Waves

The Polarizations of Gravitational Waves

Expected properties of the first gravitational wave signal detected with pulsar timing arrays

Estimates of maximum energy density of cosmological gravitational-wave backgrounds

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