Bouncing black holes in quantum gravity and the Fermi gamma-ray excess

Barrau, A.; Bolliet, Boris; Schutten, Marrit; Vidotto, Francesca

doi:10.1016/j.physletb.2017.05.040

Cited by 32 publications

(34 citation statements)

References 31 publications

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“…While what we said above holds in the case of shortlived bounces of typical timescale τ (1) , more complex is the case of long-lived bounces with τ = τ (2) , for which several phenomenological studies have been performed in the literature [52,53,164,165]. In this case no relevant signal is expected up to this timescale while two distinct components are predicted as being associated to the typical size of the exploding object (infrared component) and to the typical energy of the universe at the moment of its formation (ultraviolet component).…”

Section: Burstsmentioning

confidence: 91%

“…For primordial black holes whose lifetime is of the order of the Hubble time, it was shown that the infrared component of the signal could get up to the GeV scale and be peaked in the MeV, while the ultraviolet part of the burst is expected to be in the TeV range [164,165]. If confirmed by more accurate modelling, this would place the search for the bursts associated to bouncing geometries within the realm of current high energy astrophysics experiments (provided that a sufficient number of primordial black holes is created in the early universe).…”

Section: Burstsmentioning

confidence: 99%

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Phenomenological aspects of black holes beyond general relativity

et al. 2018

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While singularities are inevitable in the classical theory of general relativity, it is commonly believed that they will not be present when quantum gravity effects are taken into account in a consistent framework. In particular, the structure of black holes should be modified in frameworks beyond general relativity that aim at regularizing singularities. Being agnostic on the nature of such theory, in this paper we classify the possible alternatives to classical black holes and provide a minimal set of phenomenological parameters that describe their characteristic features. The introduction of these parameters allows us to study, in a largely model-independent manner and taking into account all the relevant physics, the phenomenology associated with these quantummodified black holes. We perform an extensive analysis of different observational channels and obtain the most accurate characterization of the viable constraints that can be placed using current data. Aside from facilitating a critical revision of previous work, this analysis also allows us to highlight how different channels are capable of probing certain features but are oblivious to others, and pinpoint the theoretical aspects that should be addressed in order to strengthen these tests.

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Section: Burstsmentioning

confidence: 91%

Section: Burstsmentioning

confidence: 99%

Phenomenological aspects of black holes beyond general relativity

et al. 2018

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“…Here we have assumed for simplicity that the internal volume v is conserved in this transition. A more precise account of this process will be studied elsewhere (for the tentative phenomenology derived from this process, see [33][34][35][36][37][38][39]).…”

Section: White To Black Instabilitymentioning

confidence: 99%

Small Black/White Hole Stability and Dark Matter

Rovelli

Vidotto

2018

Universe

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We show that the expected lifetime of white holes formed as remnants of evaporated black holes is consistent with their production at reheating. We give a simple quantum description of these objects and argue that a quantum superposition of black and white holes with large interiors is stable, because it is protected by the existence of a minimal eigenvalue of the area, predicted by Loop Quantum Gravity. These two results support the hypothesis that a component of dark matter could be formed by small black hole remnants. I. REMNANTSThe possibility that remnants of evaporated black holes form a component of dark matter was suggested by MacGibbon [1] thirty years ago and has been explored by many authors [2][3][4][5][6][7][8][9]. There are no strong observational constraints on this possible contribution to dark matter [10]; the weak point of this scenario has been, so far, the obscurity of the physical nature of the remnants.The situation has changed recently because of the realisation that conventional physics provides a candidate for remnants: small-mass white holes with a large interiors [11][12][13]. In addition, quantum gravity indicates that these are indeed produced at the end of the evaporation [14-18]. Here we show that the remnant lifetime predicted in [16] is remarkably consistent with the production of primordial black holes at the end of inflation. More precisely, the rather strict constraints that the model sets on the time scales of the lifetime of black and white holes happen to match with a cosmological window where primordial black hole production is expected. A preliminary version of this result was posted in [19].Open questions are the stability and the eventual quantum properties of these remnants. It was suggested in [16] that these remnants may be stable because quantum gravity dumps the Planck scale perturbations required to trigger their instability. Here we analyse the situation a bit more in detail by studying the stability of the remnants using a simple quantum model that captures the dynamical processes black and white holes can undergo. The model indicates that a quantum superposition of Planck size white and black holes should be stable, because of the large interior volume and the area gap, i.e. the presence of a minimal non-vanishing eigenvalue in the area spectrum according to Loop Quantum Gravity.These two results support the hypothesis that a component of dark matter could be formed by small black hole remnants. II. WHITE HOLESThe difference between a black hole and a white hole is not very pronounced. Observed from the outside (say from the exterior of a sphere of radius r = 2m + > 2m, where m is the mass of the hole) and for a finite amount of time, a white hole cannot be distinguished from a black hole. This is clear from the usual Schwarzschild line element, which is symmetric under time reversal, and therefore describes equally well the exterior of a black hole and the exterior of a white hole. Equivalently, zone II of the maximal extension of the Schwarzschild solution is ...

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“…. Applying these field equations in the FRW metric (1), focusing on the flat case, and assuming the usual matter perfect fluid (12), one obtains the following modified Friedmann equations [51]:…”

Section: Finsler-like Gravity On a Tangent Bundlementioning

confidence: 99%

“…The violation of null energy condition needs to be handled with care, in order not to spoil the usual thermal history and the sequence of epochs after the bounce. Nevertheless, such violations can easily be acquired from modified [7] or quantum gravity [12]. In particular, they can be eas- * Electronic address: geminas@phys.uoa.gr † Electronic address: msaridak@phys.uoa.gr ‡ Electronic address: pstavrin@math.uoa.gr § Electronic address: alktrian@phys.uoa.gr ily acquired in the Pre-Big-Bang [13,14] and the Ekpyrotic [15,16] models, in gravity actions with higher order corrections [17,18], in f (R) gravity [19,20], in f (T) gravity [21], in braneworld scenarios [22,23], in non-relativistic gravity [24][25][26], in Galileon theory [27,28], in massive gravity [29], in Lagrange modified gravity [30], in loop quantum cosmology [31][32][33], etc.…”

Section: Introductionmentioning

confidence: 99%

Bounce Cosmology in Generalized Modified Gravities

et al. 2019

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We investigate the bounce realization in the framework of generalized modified gravities arising from Finsler and Finsler-like geometries. In particular, the richer intrinsic geometrical structure is reflected in the appearance of extra degrees of freedom in the Friedmann equations that can drive the bounce. We examine various Finsler and Finsler-like constructions. In the cases of general very special relativity as well as of Finsler-like gravity on the tangent bundle we show that a bounce cannot be easily obtained. However, in the Finsler-Randers space the induced scalar anisotropy can fulfill the bounce conditions and bouncing solutions are easily obtained. Finally, for the general class of theories that include a nonlinear connection a new scalar field is induced, leading to a scalar-tensor structure that can easily drive a bounce. These features reveal the capabilities of Finsler and Finsler-like geometries. 95.36.+x, 04.50.Kd

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Bouncing black holes in quantum gravity and the Fermi gamma-ray excess

Cited by 32 publications

References 31 publications

Phenomenological aspects of black holes beyond general relativity

Phenomenological aspects of black holes beyond general relativity

Small Black/White Hole Stability and Dark Matter

Bounce Cosmology in Generalized Modified Gravities

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