Gravity stabilizes itself

Chakraborty, Sumanta; SenGupta, Soumitra

doi:10.1140/epjc/s10052-017-5138-5

Cited by 27 publications

(28 citation statements)

References 89 publications

(130 reference statements)

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“…This in turn is expected to leave some observable imprint on the strong field tests for gravitational interaction. To understand how the gravitational dynamics on the brane is modified in a quantitative manner, the higher dimensional gravitational field equations are expressed in terms of the four dimensional quantities [29][30][31][32][33][34]. Black hole solutions associated with such effective gravitational field equations [30,31,35,36] often inherit a tidal charge from the extra dimensions which unlike GR can also be negative.…”

Section: Introductionmentioning

confidence: 99%

Silhouette of M87*: A new window to peek into the world of hidden dimensions

2020

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The recent observation of the shadow of the supermassive black hole M87*, located at the centre of the M87 galaxy, by the Event Horizon Telescope collaboration has opened up a new window to probe the strong gravity regime. In this paper, we explicitly demonstrate the consequences of this observation on brane world black hole, whose characteristic feature being existence of a negative tidal charge. Our results are based on three observables associated with the shadow of M87*, namely, deviation from circularity, axis ratio and angular diameter of the shadow. These explicitly demonstrate that the existence of a negative tidal charge parameter, marking a deviation from general relativity, is more favoured.

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Section: Introductionmentioning

confidence: 99%

Silhouette of M87*: A new window to peek into the world of hidden dimensions

2020

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“…Consequently, there have been several approaches to modify the structure of the gravitational action. Among the various proposals the most prominent ones include, e.g., f (R) gravity [28][29][30][31][32][33], Lovelock theories [34][35][36][37][38][39][40], scalar-tensor theories/Horndeski models [41][42][43][44][45][46][47][48][49][50] and theories with extra spatial dimensions [51][52][53][54][55][56][57][58][59][60][61][62] (see also [63]).…”

Section: Introductionmentioning

confidence: 99%

“…The most widely used observational probe for extra dimensions come from particle physics experiments [77][78][79][80][81][82][83]. In addition, they have interesting implications in inflationary cosmology [84][85][86][87][88][89][90][91][92][93][94] and often offer exciting surrogates to the elusive dark energy [51][52][53][54][55][56][57][58][59][60][61][62] and dark matter [95][96][97][98][99]. In the context of gravitational waves they modify the quasi-normal modes emanating from the perturbed black holes with signatures distinct from general relativity [100][101][102][103][104][105].…”

Section: Introductionmentioning

confidence: 99%

Decoding signatures of extra dimensions and estimating spin of quasars from the continuum spectrum

2019

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Continuum spectrum emitted by the accretion disk around quasars hold a wealth of information regarding the strong gravitational field produced by the massive central object. Such strong gravity regime is often expected to exhibit deviations from general relativity (GR) which may manifest through the presence of extra dimensions. Higher dimensions, which serve as the corner stone for string theory and M-theory can act as promising alternatives to dark matter and dark energy with interesting implications in inflationary cosmology, gravitational waves and collider physics. Therefore it is instructive to investigate the effect of more than four spacetime dimensions on the black hole continuum spectrum which provide an effective astrophysical probe to the strong gravity regime. To explore such a scenario, we compute the optical luminosity emitted by a thin accretion disk around a rotating supermassive black hole albeit in the presence of extra dimensions. The background metric resembles the Kerr-Newmann spacetime in GR where the tidal charge parameter inherited from extra dimensions can also assume negative signature. The theoretical luminosity computed in such a background is contrasted with optical observations of eighty quasars. The difference between the theoretical and observed luminosity for these quasars is used to infer the most favoured choice of the rotation parameter for each quasar and the tidal charge parameter. This has been achieved by minimizing/maximizing several error estimators, e.g., χ 2 , Nash-Sutcliffe efficiency, index of agreement etc. Intriguingly, all of them favour a negative value for the tidal charge parameter, a characteristic signature of extra dimensions. Thus accretion disk does provide a significant possibility of exploring the existence of extra dimensions through its close correspondence with the strong gravity regime.

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“…Among the modifications of the Einstein-Hilbert action originating from the inclusion of higher curvature terms, a few are of considerable interest. In particular, f (R) theories of gravity has drawn significant interest in the past few years due to its ability to explain the late time cosmic acceleration [21][22][23][24][25][26][27][28][29][30][31][32][33] and its close correspondence with scalar-tensor theories of gravity [34][35][36][37][38][39][40][41]. In addition Lovelock theories of gravity [42][43][44][45][46][47][48][49], f (T ) gravity [50][51][52][53][54][55], higher dimensional along with higher curvature modifications to gravitational dynamics [56][57][58][59][60][61] play crucial roles in explaining various scenarios among the alternative gravity theories.…”

Section: Introductionmentioning

confidence: 99%

Horndeski theories confront the Gravity Probe B experiment

Mukherjee

Chakraborty

2018

Phys. Rev. D

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In this work we have investigated various properties of a spinning gyroscope in the context of Horndeski theories. In particular, we have focused on two specific situations -(a) when the gyroscope follows a geodesic trajectory and (b) when it is endowed with an acceleration. In both these cases, besides developing the basic formalism, we have also applied the same to understand the motion of a spinning gyroscope in various static and spherically symmetric spacetimes pertaining to Horndeski theories. Starting with the Schwarzschild de-Sitter spacetime as a warm up exercise, we have presented our results for two charged Galileon black holes as well as for a black hole in scalar coupled Einstein-Gauss-Bonnet gravity. In all these cases we have shown that the spinning gyroscope can be used to distinguish black holes from naked singularities. Moreover, using the numerical estimation of the geodetic precession from the Gravity Probe B experiment, we have constrained the gauge/scalar charge of the black holes in these Horndeski theories. Implications are also discussed. * sm13ip029@iiserkol.ac.in

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Gravity stabilizes itself

Cited by 27 publications

References 89 publications

Silhouette of M87*: A new window to peek into the world of hidden dimensions

Silhouette of M87*: A new window to peek into the world of hidden dimensions

Decoding signatures of extra dimensions and estimating spin of quasars from the continuum spectrum

Horndeski theories confront the Gravity Probe B experiment

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