Horizonless, singularity-free, compact shells satisfying NEC

Shankar, Karthik H.

doi:10.1007/s10714-017-2196-9

Cited by 2 publications

(1 citation statement)

References 21 publications

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“…THEDgravity presents a simple solution by preventing the extreme inhomogeneity-buildup into black holes. It has been shown that there can exist extremely compact objects that does not violate the NEC [22], which would otherwise be expected to collapse into black holes in the context of GR. That is, finite pressure can restrain the gravitational collapse of a massive object even after it has shrunk to an arbitrarily small size, thus preventing the formation of singularity while leaving the exterior geometry virtually indistinguishable from that of a black hole.…”

Section: B Bounded Oscillating Universementioning

confidence: 99%

Eternally oscillating zero energy universe

Shankar

2020

Gen Relativ Gravit

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The question of whether the universe is eternal or if it had a singular moment of creation is deeply intriguing. Although different versions of steady state and oscillatory models of eternal universe have been envisaged, empirical evidence suggests a singular moment of creation at the big bang. Here we analyze the oscillatory solutions for the universe in a modified theory of gravity THED (Torsion Hides Extra-Dimension) and evaluate them by fitting Type 1a supernovae redshift data. THEDgravity exactly mimics General Relativity at the kinematical level, while the modifications in its dynamical equations allow the universe to bounce between a minimum size and a maximum size with a zero average energy within each oscillation. The optimally fit oscillatory solutions correspond to a universe with (i) a small matter density requiring little to no dark matter, (ii) a significantly negative spatial curvature, (iii) a tiny negative dark energy, (iv) and an arbitrarily large maxima and small minima whose exact values depend on the tinyness of the dark energy, which can't be empirically constrained. Alternatively, there exists non-oscillating solutions that appear as an ever-expanding universe from a single bounce at some minimum size preceded by a collapse from the infinite past. These ever-expanding solutions indeed fit the redshift data marginally better than the oscillating solutions and are at par with the best fit of standard big bang theory. They accommodate a range of matter densities requiring dark matter, positive dark energy and positive spatial curvature. A qualitative analysis of CMB power spectrum with the modified dynamical equations predicts a negative spatial curvature for the universe, in stark contrast to a near-zero curvature in the standard big bang theory. An independent constraint on the spatial curvature can further shed light on discriminating the ever expanding and oscillatory universe scenarios.

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Section: B Bounded Oscillating Universementioning

confidence: 99%

Eternally oscillating zero energy universe

Shankar

2020

Gen Relativ Gravit

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Constraining black hole horizon effects by LIGO-Virgo detections of inspiralling binary black holes

Lai

2018

Phys. Rev. D

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General relativity predicts mass and spin growth of an inspiralling black hole due to an energy-momentum flux flowing through the black-hole horizon. The leading-order terms of this horizon flux introduce 2.5 and 3.5 post-Newtonian corrections to inspiral motions of binary black holes. The corrections may be measurable by gravitational waves detectors. Since the proper improvements to general relativity is still a mystery, it is possible that the true modified gravity theory introduces negligible direct corrections to the geodesics of test masses, while near horizon corrections are observable. We introduce a parameterization to describe arbitrary mass and spin growth of inspiralling black holes. Comparing signals of gravitational waves and a waveform model with parameterized horizon flux corrections, deviations from general relativity can be constrained. We simulate a set of gravitational waves signals following an astrophysical distribution with horizon flux modifications. Then, we perform a Bayesian analysis to obtain the expected constraints from the simulated response of the Advanced LIGO-Virgo detector network to the simulated signals. We show that the constraint can be improved by stacking multiple detections. The constraints of modified horizon flux can be used to test a specific class of modified gravity theories which predict dominant corrections near black-hole horizons over other types of corrections to general relativity. To support Hawking's area theorem at 90% confidence level, over 10000 LIGO-Virgo detections are required. Within the lifetime of LIGO and Einstein Telescope, a future ground-based gravitational wave detector, near horizon corrections of modified gravity theories are potentially detectable if one of the modified gravity theory is true and the theory predicts a strong correction. arXiv:1807.01840v3 [gr-qc]

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Horizonless, singularity-free, compact shells satisfying NEC

Cited by 2 publications

References 21 publications

Eternally oscillating zero energy universe

Eternally oscillating zero energy universe

Constraining black hole horizon effects by LIGO-Virgo detections of inspiralling binary black holes

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