Torres Herrera, Ramon
Total activity: 25
Research group
DF - Nonlinear Fluid Dynamics
Department
Department of Applied Physics
School
Barcelona School of Architecture (ETSAB)
E-mail
ramon.torres-herreraupc.edu
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1 to 25 of 25 results
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    Singularity free gravitational collapse in an effective dynamical quantum spacetime  Open access

     Torres Herrera, Ramon; Fayos Valles, Francisco
    Physics letters B
    Date of publication: 2014-06-02
    Journal article

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    We model the gravitational collapse of heavy massive shells including its main quantum corrections. Among these corrections, quantum improvements coming from Quantum Einstein Gravity are taken into account, which provides us with an effective quantum spacetime. Likewise, we consider dynamical Hawking radiation by modeling its back-reaction once the horizons have been generated. Our results point towards a picture of gravitational collapse in which the collapsing shell reaches a minimum non-zero radius (whose value depends on the shell initial conditions) with its mass only slightly reduced. Then, there is always a rebound after which most (or all) of the mass evaporates in the form of Hawking radiation. Since the mass never concentrates in a single point, no singularity appears. (C) 2014 The Authors. Published by Elsevier B.V.

    We model the gravitational collapse of heavy massive shells including its main quantum corrections. Among these corrections, quantum improvements coming from Quantum Einstein Gravity are taken into account, which provides us with an effective quantum spacetime. Likewise, we consider dynamical Hawking radiation by modeling its back-reaction once the horizons have been generated. Our results point towards a picture of gravitational collapse in which the collapsing shell reaches a minimum non-zero radius (whose value depends on the shell initial conditions) with its mass only slightly reduced. Then, there is always a rebound after which most (or all) of the mass evaporates in the form of Hawking radiation. Since the mass never concentrates in a single point, no singularity appears.

    Postprint (author’s final draft)

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    On how energy conservation might prevent black hole explosions and violations of the third law  Open access

     Torres Herrera, Ramon; Fayos Valles, Francisco
    International journal of modern physics D
    Date of publication: 2013-11-12
    Journal article

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    We claim that imposing energy conservation to the emission of Hawking radiation and to the modelling of black hole evaporation might prevent black hole explosions as well as violations of the third law of black hole thermodynamics. This is specifically shown for the general class of spherically symmetric quantum black holes described by an effective quantum vacuum invariant under boosts in the radial direction. No assumptions are made with regard to the specific framework from which the quantum black holes are derived.

    We claim that imposing energy conservation to the emission of Hawking radiation and to the modeling of black hole (BH) evaporation might prevent BH explosions as well as violations of the third law of BH thermodynamics. This is specifically shown for the general class of spherically symmetric quantum BHs described by an effective quantum vacuum invariant under boosts in the radial direction. No assumptions are made with regard to the specific framework from which the quantum BHs are derived.

    Preprint of an article published in International journal of modern physics D, 23, 1, 2013, 1450009-1 - 1450009-15 10.1142/S0218271814500096 © copyright World Scientific Publishing Company http://www.worldscientific.com/worldscinet/ijmpd

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    On the interior of (quantum) black holes  Open access

     Torres Herrera, Ramon
    Physics letters B
    Date of publication: 2013-06-20
    Journal article

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    Different approaches to quantum gravity conclude that black holes may possess an inner horizon, in addition to the (quantum corrected) outer `Schwarzschild¿ horizon. In this Letter we assume the existence of this inner horizon and explain the physical process that might lead to the tunneling of particles through it. It is shown that the tunneling would produce a flux of particles with a spectrum that deviates from the pure thermal one. Under the appropriate approximation the extremely high temperature of this horizon is calculated for an improved quantum black hole. It is argued that the flux of particles tunneled through the horizons affects the dynamics of the black hole interior leading to an endogenous instability.

    Different approaches to quantum gravity conclude that black holes may possess an inner horizon, in addition to the (quantum corrected) outer ‘Schwarzschild’ horizon. In this paper we assume the existence of this inner horizon and explain the physical process that might lead to the tunneling of particles through it. It is shown that the tunneling would produce a flux of particles with a spectrum that deviates from the pure thermal one. Under the appropriate approximation the extremely high temperature of this horizon is calculated for an improved quantum black hole. It is argued that the flux of particles tunneled through the horizons affects the dynamics of the black hole interior leading to an endogenous instability.

    Published in Physics letters B by ELSEVIER. The original publication is available at http://www.sciencedirect.com/science/article/pii/S0370269313005066

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    The mechanism why colliders could create quasi-stable black holes  Open access

     Torres Herrera, Ramon; Fayos Valles, Francisco; Lorente Espin, Oscar
    International journal of modern physics D
    Date of publication: 2013-09-09
    Journal article

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    It has been postulated that black holes (BHs) could be created in particle collisions within the range of the available energies for nowadays colliders (LHC). In this paper, we analyze the evaporation of a type of BHs that are candidates for this specific behavior, namely, small BHs on a brane in a world with large extra-dimensions. We examine their evolution under the assumption that energy conservation is satisfied during the process and compare it with the standard evaporation approach. We claim that, rather than undergoing a quick total evaporation, BHs become quasi-stable. We comment on the (absence of) implications for safety of this result. We also discuss how the presence of BHs together with the correctness of the energy conservation approach might be experimentally verified.

    It has been postulated that black holes could be created in particle collisions within the range of the available energies for nowadays colliders (LHC). In this paper we analyze the evaporation of a type of black holes that are candidates for this specific behaviour, namely, small black holes on a brane in a world with large extra-dimensions. We examine their evolution under the assumption that energy conservation is satisfied during the process and compare it with the standard evaporation approach. We claim that, rather than undergoing a quick total evaporation, black holes become quasi-stable. We comment on the (absence of) implications for safety of this result. We also discuss how the presence of black holes together with the correctness of the energy conservation approach might be experimentally verified.

    Preprint of an article published in International journal of modern physics D, 22, 13, 2013, 1350086-1 - 1350086-15 10.1142/S0218271813500867 © copyright World Scientific Publishing Company http://www.worldscientific.com/worldscinet/ijmpd

  • Evaporation of (quantum) black holes and energy conservation

     Torres Herrera, Ramon; Fayos Valles, Francisco; Lorente Espín, Oscar
    Physics letters B
    Date of publication: 2013-01-28
    Journal article

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  • Cosmological voids and quantum violations of the weak energy conditions

     Torres Herrera, Ramon
    Classical and quantum gravity
    Date of publication: 2013-02-26
    Journal article

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    In this paper the consequences of quantum gravitational effects in cosmological voids are studied through the use of the well-known and reliably calculable long-range quantum corrections to the gravitational potential. The line-element corresponding to these quantum-modified voids in a Universe possessing a cosmological constant is obtained. It is shown that the quantum vacuum in the voids is interpretable, through Einstein's equations, as a highly rarefied effective anisotropic fluid permeating the voids. Contrary to the common belief that in our current epoch violations of the energy conditions only take place in relatively small regions of the Universe, it is argued that there may be extremely tiny quantum violations of the weak energy condition in cosmological voids and, therefore, in enormous regions occupying most of the volume of the Universe.

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    Mechanism of quasistabilization of primordial black holes  Open access

     Torres Herrera, Ramon
    Physical review. D, Particles, fields, gravitation, and cosmology
    Date of publication: 2013-06-17
    Journal article

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    It is argued that primordial black holes with initial masses satisfying M<1015¿¿g, instead of having explode, might currently be in a quasistable phase contributing to a tiny fraction of the measured dark matter. This statement is based on a computation of black hole evaporation in which energy conservation is taken into account that shows that the backreaction to Hawking radiation favors the quasistabilization of the black hole. The result is specifically shown for general spherically symmetric quantum black holes described by an effective metric independently of the specific framework from which it is derived. The quintessential primordial black hole is fully analyzed as an example.

    It is argued that primordial black holes with initial masses satisfying M<1015 g, instead of having explode, might currently be in a quasistable phase contributing to a tiny fraction of the measured dark matter. This statement is based on a computation of black hole evaporation in which energy conservation is taken into account that shows that the backreaction to Hawking radiation favors the quasistabilization of the black hole. The result is specifically shown for general spherically symmetric quantum black holes described by an effective metric independently of the specific framework from which it is derived. The quintessential primordial black hole is fully analyzed as an example.

  • On the effect of energy conservation on black hole evaporation

     Torres Herrera, Ramon; Fayos Valles, Francisco; Lorente Espín, Oscar
    International journal of modern physics D
    Date of publication: 2013-04-23
    Journal article

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    We consider the emission of Hawking radiation by black holes as a consequence of a tunneling process. By requiring energy conservation in the derivation of the emission rate we get a well-known deviation from an exact thermal spectrum. A model that takes into account the implications of energy conservation, as well as the back-scattered radiation, is then constructed in order to describe the evolution of black holes as they evaporate. The evaporation process in this model is compared with the results in the standard "thermal" approximation. This allows us to point out the relevance that energy conservation might have in the last stages of black hole evaporation. We also comment about the possible implications of energy conservation in the information loss paradox.

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    On the invariant causal characterization of singularities in spherically symmetric spacetimes  Open access

     Fayos Valles, Francisco; Torres Herrera, Ramon
    Classical and quantum gravity
    Date of publication: 2012-04-18
    Journal article

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    The causal character of singularities is often studied in relation to the existence of naked singularities and the subsequent possible violation of the cosmic censorship conjecture. Generally, one constructs a model in the framework of general relativity described in some specific coordinates and finds an ad hoc procedure to analyze the character of the singularity. In this paper, we show that the causal character of the zero-areal-radius (R = 0) singularity in spherically symmetric models is related to some specific invariants. In this way, if some assumptions are satisfied, one can ascertain the causal character of the singularity algorithmically through the computation of these invariants and, therefore, independent of the coordinates used in the model.

  • Invariant identification of naked singularities in spherically symmetric spacetimes

     Torres Herrera, Ramon
    Classical and quantum gravity
    Date of publication: 2012-09-10
    Journal article

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    An approach to evaporating stars and black holes  Open access

     Fayos Valles, Francisco; Torres Herrera, Ramon
    Journal of physics: conference series
    Date of publication: 2011-09-01
    Journal article

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    Many models in which the object under study loses all its mass have appeared in the literature. No doubt, the most eminent examples are the models for evaporating black holes and for evaporating stars. Here we describe a semiclassical study of these evaporating models centered on the evaporating event itself. We pay special attention to the evaporating models as a means of avoiding singularities during the collapse. In case of any pre-existing non-spacelike curvature singularity, we show that these models tend to evaporate it.

    Many models in which the object under study loses all its mass have appeared in the literature. No doubt, the most eminent examples are the models for evaporating black holes and for evaporating stars. Here we describe a semiclassical study of these evaporating models centered on the evaporating event itself. We pay special attention to the evaporating models as a means of avoiding singularities during the collapse. In case of any pre-existing non-spacelike curvature singularity, we show that these models tend to evaporate it.

  • On the causal characterization of singularities in spherically symmetric spacetimes

     Fayos Valles, Francisco; Torres Herrera, Ramon
    Classical and quantum gravity
    Date of publication: 2011-10-14
    Journal article

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  • A quantum improvement to the gravitational collapse of radiating stars

     Fayos Valles, Francisco; Torres Herrera, Ramon
    Classical and quantum gravity
    Date of publication: 2011-04-06
    Journal article

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    Local behaviour of evaporating stars and black holes around the total evaporation event  Open access

     Fayos Valles, Francisco; Torres Herrera, Ramon
    Classical and quantum gravity
    Date of publication: 2010-06-21
    Journal article

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  • An approach to evaporating stars and black holes

     Fayos Valles, Francisco; Torres Herrera, Ramon
    Spanish Relativity Meeting
    Presentation's date: 2010
    Presentation of work at congresses

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  • A class of interiors for Vaidya's radiating metric: singularity-free gravitational collapse

     Fayos Valles, Francisco; Torres Herrera, Ramon
    Classical and quantum gravity
    Date of publication: 2008-09-01
    Journal article

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  • Some aspects of bubbles and voids in a cosmological context

     Torres Herrera, Ramon
    Classical and quantum gravity
    Date of publication: 2005
    Journal article

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  • Spherically symmetric models for stars and voids II: Constrains on the radial pressures

     Fayos Valles, Francisco; Torres Herrera, Ramon
    Classical and quantum gravity
    Date of publication: 2004-02
    Journal article

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  • Spherically symmetric models for charged stars and voids: I. Charge bound

     Fayos Valles, Francisco; Senovilla, José M M; Torres Herrera, Ramon
    Classical and quantum gravity
    Date of publication: 2003-05
    Journal article

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  • CONSTRUCCION DE MODELOS DE ESTRELLAS Y BURBUJAS DE VACIO O RADIATIVAS, EN EL MARCO DE LA RELATIVIDAD GENERAL : UN PLANTEAMIENTO GLOBAL

     Torres Herrera, Ramon
    Defense's date: 2001-10-15
    Department of Applied Physics, Universitat Politècnica de Catalunya
    Theses

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  • Constructing models for stars and voids in the universe: a Comprehensive approach

     Fayos Valles, Francisco; Torres Herrera, Ramon
    XXIII Spanish Relativity Meeting
    Presentation of work at congresses

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  • Some reflections on the spherically matching

     Fayos Valles, Francisco; Senovilla, J M M; Torres Herrera, Ramon
    Encuentros Relativistas Españoles 96: Some Topics on General Relativity and Gravitational Radiation
    Presentation of work at congresses

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  • Some reflections on the spherically symmetric matching

     Fayos Valles, Francisco; Senovilla, J M M; Torres Herrera, Ramon
    Spanish relativity meeting '96
    Presentation of work at congresses

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  • General matching of two spherically symmetric spacetimes

     Fayos Valles, Francisco; Senovilla, J M M; Torres Herrera, Ramon
    Physical review. D, Particles, fields, gravitation, and cosmology
    Date of publication: 1996-10-01
    Journal article

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