Person: Garay Elizondo, Luis Javier
Universidad Complutense de Madrid
Faculty / Institute
Now showing 1 - 10 of 18
PublicationSpacetime foam as a quantum thermal bath(American Physical Society, 1998-03-23) Garay Elizondo, Luis JavierAn effective model for the spacetime foam is constructed in terms of nonlocal interactions in a classical background. In the weak coupling approximation, the evolution of the low-energy density matrix is determined by a master equation that predicts loss of quantum coherence. Moreover, spacetime foam can be described by a quantum thermal field that, apart from inducing loss of coherence, gives rise to effects such as gravitational Lamb and Stark shifts as well as quantum damping in the evolution of the low-energy observables. PublicationThermal properties of spacetime foam(Amer Physical Soc, 1998-12-15) Garay Elizondo, Luis JavierSpacetime foam can be modeled in terms of nonlocal effective interactions in a classical nonfluctuating background. Then, the density matrix for the low-energy fields evolves, in the weak-coupling approximation, according to a master equation that contains a diffusion term. Furthermore, it is argued that spacetime foam behaves as a quantum thermal field that, apart from inducing loss of coherence, gives rise to effects such as gravitational Lamb and Stark shifts as well as quantum damping in the evolution of the low-energy observables. These effects can be, at least in principle, experimentally tested. [S0556-2821(98)04524-X]. PublicationQuantum evolution in space-time foam(World Scientific Publ Co Pte Ltd, 1999-08-20) Garay Elizondo, Luis JavierIn this work, I review some aspects concerning the evolution of quantum low-energy fields in a foamlike space-time, with involved topology at the Planck scale but with a smooth metric structure at large length scales, as follows. Quantum gravitational fluctuations may induce a minimum length thus introducing an additional source of uncertainty in physics. The existence of this resolution limit casts doubts on the metric structure of space-time at the Planck scale and opens a doorway to nontrivial topologies, which may dominate Planck scale physics. This foamlike structure of space-time may show up in low-energy physics through loss of quantum coherence and mode-dependent energy shifts, for instance, which might be observable. Space-time foam introduces nonlocal interactions that can be modeled by a quantum bath, and low-energy fields evolve according to a master equation that displays such effects. Similar laws are also obtained for quantum mechanical systems evolving according to good real clocks, although the underlying Hamiltonian structure in this case establishes serious differences among both scenarios. PublicationNonorientable spacetime tunneling(Amer Physical Soc, 1999-03-15) González Díaz, Pedro F.; Garay Elizondo, Luis JavierMisner space is generalized to have the nonorientable topology of a Klein bottle, and it is shown that, in a classical spacetime with multiply connected space slices having such a topology, closed timelike curves are formed. Different regions on the Klein bottle surface can be distinguished which are separated by apparent horizons fixed at particular values of the two angular variables that enter the metric. Around the throat of this tunnel (which we denote a Klein bottlehole), the position of these horizons dictates an ordinary and exotic matter distribution such that, in addition to the known diverging lensing action of wormholes, a converging lensing action is also present at the mouths. Associated with this matter distribution, the accelerating version of this Klein bottlehole shows four distinct chronology horizons, each with its own nonchronal region. A calculation of the quantum vacuum fluctuations performed by using the regularized two-point Hadamard function shows that each chronology horizon nests a set of polarized hypersurfaces where the renormalized momentum-energy tensor diverges. This quantum instability can be prevented if we take the accelerating Klein bottlehole to be a generalization of a modified Misner space in which the period of the closed spatial direction is time dependent. In this case, the nonchronal regions and closed timelike curves cannot exceed a minimum size of the order the Planck scale. [S0556-2821(99)01906-2]. PublicationQuantum evolution according to real clocks(American Physical Society, 1999-05) Egusquiza, Iñigo L.; Garay Elizondo, Luis Javier; Raya, José M.We characterize good clocks, which are naturally subject to fluctuations, in statistical terms. We also obtain the master equation that governs the evolution of quantum systems according to these clacks and find its general solution. This master equation is diffusive and produces loss of coherence, Moreover, real clocks can he described in terms of effective interactions that are nonlocal in time. Alternatively, they can be modeled by an effective thermal bath coupled to the system. [S1050-2947(99)04905-7]. PublicationCircular strings, wormholes, and minimum size(Amer Physical Soc, 1997-06-15) Garay Elizondo, Luis Javier; González Díaz, Pedro F.; Mena Marugán, Guillermo A.; Raya, José M.The quantization of circular strings in an anti-de Sitter background spacetime is performed, obtaining a discrete spectrum for the string mass. A comparison with a four-dimensional homogeneous and isotropic spacetime coupled to a conformal scalar field shows that the string radius and the scale factor have the same classical solutions and that the quantum theories of these two models are formally equivalent. However, the physically relevant observables of these two systems have different spectra, although they are related to each other by a specific one-to-one transformation. We finally obtain a discrete spectrum for the spacetime size of both systems, which presents a nonvanishing lower bound. 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. PublicationQuantum-gravity and minimum length(World Scientific Publ Co Pte Ltd, 1995-01-20) Garay Elizondo, Luis JavierThe existence of a fundamental scale, a lower bound to any output of a position measurement, seems to be a model-independent feature of quantum gravity. In fact, different approaches to this theory lead to this result. The key ingredients for the appearance of this minimum length are quantum mechanics, special relativity and general relativity. As a consequence, classical notions such as causality or distance between events cannot be expected to be applicable at this scale. They must be replaced by some other, yet unknown, structure. PublicationThiemann transform for gravity with matter fields(IOP Publishing Ltd, 1998-12) Garay Elizondo, Luis Javier; Mena Marugán, Guillermo A.The generalized Wick transform discovered by Thiemann provides a well established relation between the Euclidean and Lorentzian theories of general relativity. We extend this Thiemann transform to the Ashtekar formulation for gravity coupled with spin-1/2 fermions, a non-Abelian Yang-Mills field and a scalar field. It is proved that, on functions of the gravitational and matter phase space variables, the Thiemann transform is equivalent to the composition of an inverse Wick rotation and a constant complex scale transformation of all fields. This result also holds for functions that depend on the shift vector, the lapse function and the Lagrange multipliers of the Yang-Mills and gravitational Gauss constraints, provided that the Wick rotation is implemented by means of an analytic continuation of the lapse. In this way, the Thiemann transform is furnished with a geometric interpretation. Finally, we confirm the expectation that the generator of the Thiemann transform can be determined just from the spin of the fields and give a simple explanation for this fact. PublicationThe dynamical structure of higher dimensional Chern-Simons theory(Elsevier, 1996-09-30) Banados, M.; Garay Elizondo, Luis Javier; Henneaux, M.Higher dimensional Chern-Simons theories, even though constructed along the same topological pattern as in 2 + 1 dimensions, have been shown recently to have generically a non-vanishing number of degrees of freedom. In this paper, we carry out the complete Dirac Hamiltonian analysis (separation of first and second class constraints and calculation of the Dirac bracket) for a group G x U(1). We also study the algebra of surface charges that arise in the presence of boundaries and show that it is isomorphic to the WZW(4) discussed in the literature. Some applications are then considered. It is shown, in particular, that Chem-Simons gravity in dimensions greater than or equal to five has a propagating torsion.