Person: Garay Elizondo, Luis Javier
Universidad Complutense de Madrid
Faculty / Institute
Now showing 1 - 7 of 7
PublicationThe trans-Planckian problem as a guiding principle(Int School Advanced Studies, 2011-11) Barbado, L. C.; Barceló, C.; Garay Elizondo, Luis Javier; Jannes, GilWe use the avoidance of the trans-Planckian problem of Hawking radiation as a guiding principle in searching for a compelling scenario for the evaporation of black holes or black-hole-like objects. We argue that there exist only three possible scenarios, depending on whether the classical notion of long-lived horizon is preserved by high-energy physics and on whether the dark and compact astrophysical objects that we observe have long-lived horizons in the first place. Along the way, we find that i) a theory with high-energy superluminal signalling and a long-lived trapping horizon would be extremely unstable in astrophysical terms and that i i) stellar pulsations of objects hovering right outside but extremely close to their gravitational radius can result in a mechanism for Hawking-like emission. PublicationWormhole effective interactions in anti-de Sitter spacetime(World Scientific, 1998-08) 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. PublicationStability analysis of sonic horizons in Bose-Einstein condensates(Amer Physical Soc, 2006-07) Barceló, C.; Cano, A.; Garay Elizondo, Luis Javier; Jannes, G.We examine the linear stability of various configurations in Bose-Einstein condensates with steplike sonic horizons. These configurations are chosen in analogy with gravitational systems with a black hole horizon, a white hole horizon, and a combination of both. We discuss the role of different boundary conditions in this stability analysis, paying special attention to their meaning in gravitational terms. We highlight that the stability of a given configuration, not only depends on its specific geometry, but especially on these boundary conditions. Under boundary conditions directly extrapolated from those in standard general relativity, black hole configurations, white hole configurations, and the combination of both into a black hole-white hole configuration are shown to be stable. However, we show that under other (less stringent) boundary conditions, configurations with a single black hole horizon remain stable, whereas white hole and black hole-white hole configurations develop instabilities associated to the presence of the sonic horizons. PublicationAsymptotically anti-de Sitter wormholes(Amer Physical Soc, 1996-03-15) Barceló, C.; Garay Elizondo, Luis Javier; Gonzalez Diaz, P. F.; Mena Marugán, Guillermo A.Starting with a procedure for dealing with general asymptotic behavior, we construct a quantum theory for asymptotically anti-de Sitter wormholes. We follow both the path integral formalism and the algebraic quantization program proposed by Ashtekar. By adding suitable surface terms, the Euclidean action of the asymptoically anti-de Sitter wormholes can be seen to be finite and gauge invariant. This action determines an appropriate variational problem for wormholes. We also obtain the wormhole wave functions of the gravitational model and show that all the physical states of the quantum theory are superpositions of wormhole states. PublicationSensitivity of Hawking radiation to superluminal dispersion relations(Amer Physical Soc, 2009-01) Barceló, C.; Garay Elizondo, Luis Javier; Jannes, G.We analyze the Hawking radiation process due to collapsing configurations in the presence of superluminal modifications of the dispersion relation. With such superluminal dispersion relations, the horizon effectively becomes a frequency-dependent concept. In particular, at every moment of the collapse, there is a critical frequency above which no horizon is experienced. We show that, as a consequence, the late-time radiation suffers strong modifications, both quantitative and qualitative, compared to the standard Hawking picture. Concretely, we show that the radiation spectrum becomes dependent on the measuring time, on the surface gravities associated with different frequencies, and on the critical frequency. Even if the critical frequency is well above the Planck scale, important modifications still show up. PublicationTwo faces of quantum sound(Amer Physical Soc, 2010-08-25) Barceló, C.; Garay Elizondo, Luis Javier; Jannes, G.Fluctuations around a Bose-Einstein condensate can be described by means of Bogolubov theory leading to the notion of quasiparticle and antiquasiparticle familiar to nonrelativistic condensed-matter practitioners. On the other hand, we already know that these perturbations evolve according to a relativistic Klein-Gordon equation in the long-wavelength approximation. For shorter wavelengths, we show that this equation acquires nontrivial corrections which modify the Klein-Gordon product. In this approach, quasiparticles can also be defined (up to the standard ambiguities due to observer dependence). We demonstrate that-in the low-energy as well as in the high-energy regimes-both concepts of quasiparticle are actually the same, regardless of the formalism (Bogolubov or Klein-Gordon) used to describe them. These results also apply to any barotropic, inviscid, irrotational fluid, with or without quantum potential. Finally, we illustrate how the quantization of these systems of quasiparticles proceeds by analyzing a stationary configuration containing an acoustic horizon. We show that there are several possible choices of a regular vacuum state, including a regular generalization of the Boulware vacuum. Issues such us Hawking radiation crucially depend on this vacuum choice. PublicationQuantum fields in anti-de Sitter wormholes(Amer Physical Soc, 1998-03-15) Barceló, C.; Garay Elizondo, Luis JavierWe study the effects of asymptotically anti-de Sitter wormholes in low-energy field theory and give a general prescription for obtaining the local effective interaction terms induced by them. The choice of vacuum for the matter fields selects a basis of the Hilbert space of anti-de Sitter wormholes whose elements can be interpreted as states containing a given number of particles. This interpretation is subject to the same kind of ambiguity in the definition of a particle as that arising from quantum field theory in curved spacetime.