Semiclassical dynamics of horizons in spherically symmetric collapse

Tavakoli, Yaser; Marto, João; Dapor, Andrea

doi:10.1142/s0218271814500618

Cited by 34 publications

(28 citation statements)

References 43 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Besides the model presented here, non-singular scenarios have been reported in the literature within various models such as f (R) theories of gravity in the Palatini [86] and metric [87] formalisms, nonsingular cosmological settings in the presence of a spinning fluid in the context of EC theory [88], bouncing scenarios in brane models [89][90][91][92][93], and modified Gauss-Bonnet gravity [94] (see also [95] for recent review). While the spacetime singularities could generically occur as the end-product of a continual gravitational collapse, it is widely believed that in the very final stages of the collapse where the scales are comparable to the Planck length and extreme gravity regions are dominant, quantum corrections could generate a strong negative pressure in the interior of the cloud to finally resolve the classical singularity [96][97][98][99][100][101][102][103][104][105][106][107]. Finally, as we come near the end of this paper we should point out that quantum effects due to particle creation could possibly avoid the cosmological [108][109][110][111] as well as astrophysical singularities [112].…”

Section: Discussionmentioning

confidence: 99%

Collapse and dispersal of a homogeneous spin fluid in Einstein–Cartan theory

2015

View full text Add to dashboard Cite

In the present work, we revisit the process of gravitational collapse of a spherically symmetric homogeneous dust fluid which is described by the OppenheimerSnyder (OS) model (Oppenheimer and Snyder in Phys Rev D 56:455, 1939). We show that such a scenario would not end in a spacetime singularity when the spin degrees of freedom of fermionic particles within the collapsing cloud are taken into account. To this purpose, we take the matter content of the stellar object as a homogeneous Weyssenhoff fluid. Employing the homogeneous and isotropic FLRW metric for the interior spacetime setup, it is shown that the spin of matter, in the context of a negative pressure, acts against the pull of gravity and decelerates the dynamical evolution of the collapse in its later stages. Our results show a picture of gravitational collapse in which the collapse process halts at a finite radius, whose value depends on the initial configuration. We thus show that the spacetime singularity that occurs in the OS model is replaced by a non-singular bounce beyond which the collapsing cloud re-expands to infinity. Depending on the model parameters, one can find a minimum value for the boundary of the collapsing cloud or correspondingly a threshold value for the mass content below which the horizon formation can be avoided. Our results are supported by a thorough numerical analysis.

show abstract

Section: Discussionmentioning

confidence: 99%

Collapse and dispersal of a homogeneous spin fluid in Einstein–Cartan theory

2015

View full text Add to dashboard Cite

show abstract

“…Following Ref. [13], we consider here an effective theory of gravity where the corrections to the energy density (23) take the form…”

Section: Quantum-inspired Collapsementioning

confidence: 99%

“…Such an approach was used in Ref. [13], where LQG corrections to the collapse of a scalar field were considered. Here, we will implement a similar strategy for the collapse of both a cloud of non interacting particles (dust) and a perfect fluid with a linear equation of state that describes radiation.…”

Section: Introductionmentioning

confidence: 99%

Non-singular quantum-inspired gravitational collapse

2013

View full text Add to dashboard Cite

We consider general relativistic homogeneous gravitational collapses for dust and radiation. We show that replacing the density profile with an effective density justified by some quantum gravity framework leads to the avoidance of the final singularity. The effective density acts on the collapsing cloud by introducing an isotropic pressure, which is negligible at the beginning of the collapse and becomes negative and dominant in the strong field regime. Event horizons never form and therefore the outcome of the collapse is not a black hole, in the sense that there are no regions causally disconnected from future null infinity. Apparent horizons form when the mass of the object exceeds a critical value, disappear when the matter density approaches an upper bound and gravity becomes very weak (asymptotic freedom regime), form again after the bounce as a consequence of the decrease in the matter density, and eventually disappear when the density becomes too low and the matter is radiated away. The possibility of detecting radiation coming from the high density region of a collapsing astrophysical object in which classically there would be the creation of a singularity could open a new window to experimentally test theories of quantum gravity.Comment: 11 pages, 6 figures. v2: refereed versio

show abstract

“…G N is replaced by a function G of the radial coordinate, which is used to reproduce the effects of (3.1) or a generic quantum effective action for gravity [15,60]. To this aim we start from the exterior solution and we reconstruct the interior.…”

Section: Black Holesmentioning

confidence: 99%

Black supernovae and black holes in non-local gravity

Bambi

Malafarina

Modesto

2016

J. High Energ. Phys.

View full text Add to dashboard Cite

In a previous paper, we studied the interior solution of a collapsing body in a non-local theory of gravity super-renormalizable at the quantum level. We found that the classical singularity is replaced by a bounce, after which the body starts expanding. A black hole, strictly speaking, never forms. The gravitational collapse does not create an event horizon but only an apparent one for a finite time. In this paper, we solve the equations of motion assuming that the exterior solution is static. With such an assumption, we are able to reconstruct the solution in the whole spacetime, namely in both the exterior and interior regions. Now the gravitational collapse creates an event horizon in a finite comoving time, but the central singularity is approached in an infinite time. We argue that these black holes should be unstable, providing a link between the scenarios with and without black holes. Indeed, we find a non catastrophic ghost-instability of the metric in the exterior region. Interestingly, under certain conditions, the lifetime of our black holes exactly scales as the Hawking evaporation time.

show abstract

Semiclassical dynamics of horizons in spherically symmetric collapse

Cited by 34 publications

References 43 publications

Collapse and dispersal of a homogeneous spin fluid in Einstein–Cartan theory

Collapse and dispersal of a homogeneous spin fluid in Einstein–Cartan theory

Non-singular quantum-inspired gravitational collapse

Black supernovae and black holes in non-local gravity

Contact Info

Product

Resources

About