Person: Garay Elizondo, Luis Javier
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First Name
Luis Javier
Last Name
Garay Elizondo
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Department
Física Teórica
Area
Física Teórica
Identifiers
69 results
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Now showing 1 - 10 of 69
Item Quantum entanglement produced in the formation of a black hole(Physical review D, 2010) Martin Martinez, Eduardo; Garay Elizondo, Luis Javier; León, JuanA field in the vacuum state, which is in principle separable, can evolve to an entangled state in a dynamical gravitational collapse. We will study, quantify, and discuss the origin of this entanglement, showing that it could even reach the maximal entanglement limit for low frequencies or very small black holes, with consequences in micro-black hole formation and the final stages of evaporating black holes. This entanglement provides quantum information resources between the modes in the asymptotic future (thermal Hawking radiation) and those which fall to the event horizon. We will also show that fermions are more sensitive than bosons to this quantum entanglement generation. This fact could be helpful in finding experimental evidence of the genuine quantum Hawking effect in analog models.Item Unitary quantization of a scalar charged field and Schwinger effect(Journal of High Energy Physics, 2020) Garay Elizondo, Luis Javier; Martín Caro, Alberto García; Martín Benito, MercedesQuantum field theory in curved spacetimes suffers in general from an infinite ambiguity in the choice of Fock representation and associated vacuum. In cosmological backgrounds, the requirement of a unitary implementation of the field dynamics in the physical Hilbert space of the theory is a good criterion to ameliorate such ambiguity. In- deed, this criterion, together with a unitary implementation of the symmetries of the equations of motion, leads to an equivalence class of unitarily equivalent quantizations that, even though it is still formed by an infinite number of Fock representations, is unique. In this work, we apply the procedure developed for fields in cosmological settings to analyze the quantization of a scalar field in the presence of an external electromagnetic classical field in a flat background. We find a natural Fock representation that admits a unitary implementation of the quantum field dynamics. It automatically allows to define a particle number density at all times in the evolution with the correct asymptotic behavior, when the electric field vanishes. Moreover we show the unitary equivalence of all the quantizations that fulfill our criteria, so that they form a unique equivalence class. Although we perform the field quantization in a specific gauge, we also show the equivalence between the procedures taken in different gauges.Item Gravitational production of scalar dark matter(Journal of high energy physics, 2020) Ruiz Cembranos, José Alberto; Garay Elizondo, Luis Javier; Sánchez Velázquez, José ManuelWe investigate the gravitational production of scalar dark matter particles during the inflationary and reheating epochs. The oscillatory behavior of the curvature scalarRduring the reheating phase generates two different enhancement mechanisms in the particle production. On the one hand, as it has been already discussed in previous works, it induces tachyonic instabilities in the field which are the dominant enhancement mechanism for light masses. On the other hand, we have found that it also provokes a resonant effect in the ultraviolet region of the spectrum which becomes dominant for masses in the range 10(9)GeV to 10(13)GeV. We have developed an analytical approximation to describe this resonance effect and its consequences on the ultraviolet regime. Once we have calculated the theoretical gravitational production, we constrain the possible values of the phenomenological field parameters to be considered as a dark matter candidate. We do so by comparing the theoretically predicted abundance with the observed one and ensuring that the theoretical prediction does not lead to overproduction. In particular, we find that there is a region of intermediate masses that is forbidden as they would lead to overproduction.Item Vacuum Semiclassical Gravity Does Not Leave Space for Safe Singularities(Universe, 2021) Arrechea, Julio; Barceló, Carlos; Boyanov Savov, Valentin; Garay Elizondo, Luis JavierGeneral relativity predicts its own demise at singularities but also appears to conveniently shield itself from the catastrophic consequences of such singularities, making them safe. For instance, if strong cosmic censorship were ultimately satisfied, spacetime singularities, although present, would not pose any practical problems to predictability. Here, we argue that under semiclassical effects, the situation should be rather different: the potential singularities which could appear in the theory will generically affect predictability, and so one will be forced to analyse whether there is a way to regularise them. For these possible regularisations, the presence and behaviour of matter during gravitational collapse and stabilisation into new structures will play a key role. First, we show that the static semiclassical counterparts to the Schwarzschild and Reissner–Nordström geometries have singularities which are no longer hidden behind horizons. Then, we argue that in dynamical scenarios of formation and evaporation of black holes, we are left with only three possible outcomes which could avoid singularities and eventual predictability issues. We briefly analyse the viability of each one of them within semiclassical gravity and discuss the expected characteristic timescales of their evolution.Item Emergent gauge symmetries: Yang-Mills theory(Physical Review D, 2021) Barceló, Carlos; Carballo Rubio, Raúl; Garay Elizondo, Luis Javier; García Moreno, GerardoIn this article, subleading (in 1/N) corrections to the action of the one loop dilatation operator in the su(3) sector of N = 4 super Yang-Mills theory are studied. We focus on the system of operators dual to two giant graviton systems, which have a bare dimension ∼ O(N) and are a linear combination of restricted Schur polynomials with p = 2 long columns. At the leading order the dilatation operator gives rise to the free part of an emergent Yang-Mills theory, arising from the open string excitations of the giant gravitons. We verify that the terms we study describe interactions between these open string excitations. The interactions have the U(1)×U(1) gauge invariance expected for a pair of separated branes.Item Hybrid quantum Gowdy cosmology: combining loop and Fock quantizations(Physical review D, 2008) Martín Benito, Mercedes; Garay Elizondo, Luis Javier; Mena Marugán, Guillermo A.We quantize an inhomogeneous cosmological model using techniques that include polymeric quantization. More explicitly, we construct well-defined operators to represent the constraints and find the physical Hilbert space formed by their solutions, which reproduces the conventional Fock quantization for the inhomogeneities. The initial singularity is resolved in this inhomogeneous model in an extremely simple way and without imposing special boundary conditions, thus ensuring the robustness and generality of this resolution. Furthermore, this quantization constitutes a well-founded step towards the extraction of physical results and consequences from loop quantum cosmology, given the central role of the inhomogeneities in modern cosmology.Item Analogue gravity simulation of superpositions of spacetimes(European physical journal C, 2022) Barceló, Carlos; Garay Elizondo, Luis Javier; García Moreno, GerardoTaking the principles of quantum mechanics as they stand and applying them to gravity, leads to the conclusion that one might be able to generate superpositions of spacetimes, at least formally. We analyze such a possibility from an analogue gravity perspective. We present an analogue toy model consisting of a Bose-Einstein condensate in a double-well potential and identify the states that could potentially be interpreted as superposition of effective spacetimes. These states are unstable and the source of instability from a microscopic point of view can be related to the absence of a well-defined causal structure in the effective geometric description. We explore the consequences of these instabilities and argue that they resonate with Penrose's ideas about the decay that superpositions of states with sufficiently different gravitational fields associated should experience.Item Quantum non-gravity and stellar collapse(Foundations of physics, 2011) Barceló, Carlos; Garay Elizondo, Luis Javier; Jannes, GilObservational indications combined with analyses of analogue and emergent gravity in condensed matter systems support the possibility that there might be two distinct energy scales related to quantum gravity: the scale that sets the onset of quantum gravitational effects E-B ( related to the Planck scale) and the much higher scale E-L signalling the breaking of Lorentz symmetry. We suggest a natural interpretation for these two scales: E-L is the energy scale below which a special relativistic spacetime emerges, E-B is the scale below which this spacetime geometry becomes curved. This implies that the first 'quantum' gravitational effect around E-B could simply be that gravity is progressively switched off, leaving an effective Minkowski quantum field theory up to much higher energies of the order of E-L. This scenario may have important consequences for gravitational collapse, inasmuch as it opens up new possibilities for the final state of stellar collapse other than an evaporating black hole.Item Wormhole effective interactions in anti-de Sitter spacetime(International journal of modern physics. D, Gravitation, astrophysics, cosmology, 1998) Barceló, C.; Garay Elizondo, Luis JavierThe effects of asymptotically anti-de Sitter wormholes in low-energy field theory are calculated in full detail for three different matter contents: a conformal scalar field, an electromagnetic field and gravitons. There exists a close relation between the choice of vacuum for the matter fields and the selection of a basis of the Hilbert space of anti-de Sitter wormholes. In the presence of conformal matter (i.e., conformal scalar or electromagnetic fields), this relation allows us to interpret the elements of these bases as wormhole states containing a given number of particles. This interpretation is subject to the same kind of ambiguity in the definition of particle as that arising from quantum field theory in curved spacetime. In the case of gravitons, owing to the nonconformal coupling, it is not possible to describe wormhole states in terms of their particle content.Item Hawking radiation as perceived by different observers: an analytic expression for the effective-temperature function(Classical and quantum gravity, 2012) Barbado, L. C.; Barceló, Carlos; Garay Elizondo, Luis JavierGiven a field vacuum state in a black hole spacetime, this state can be analysed in terms of how it is perceived (in terms of particle content) by different observers. This can be done by means of the effective-temperature function introduced by Barcelo et al (2011 Phys. Rev. D 83 041501). In Barbado et al (2011 Class. Quantum Grav. 28 125021), this function was analysed in a case-by-case basis for a number of interesting situations. In this work, we find a general analytic expression for the effective-temperature function which, apart from the vacuum state choice, depends on the position, the local velocity and the acceleration of the specific observer. We give a clear physical interpretation of the quantities appearing in the expression, and illustrate its potentiality with a few examples.