Garay Elizondo, Luis Javier

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First Name
Luis Javier
Last Name
Garay Elizondo
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Física Teórica
Física Teórica
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Now showing 1 - 5 of 5
  • Publication
    Derivative couplings in gravitational production in the early universe
    (Springer, 2020-09-09) Borrajo Gutierrez, Daniel; Ruiz Cembranos, José Alberto; Garay Elizondo, Luis Javier; Sánchez Velázquez, José Manuel
    Gravitational particle production in the early universe is due to the coupling of matter fields to curvature. This coupling may include derivative terms that modify the kinetic term. The most general first order action contains derivative couplings to the curvature scalar and to the traceless Ricci tensor, which can be dominant in the case of (pseudo-)Nambu-Goldstone bosons or disformal scalars, such as branons. In the presence of these derivative couplings, the density of produced particles for the adiabatic regime in the de Sitter phase (which mimics inflation) is constant in time and decays with the inverse effective mass (which in turn depends on the coupling to the curvature scalar). In the reheating phase following inflation, the presence of derivative couplings to the background curvature modifies in a nontrivial way the gravitational production even in the perturbative regime. We also show that the two couplings - to the curvature scalar and to the traceless Ricci tensor - are drastically different, specially for large masses. In this regime, the production becomes highly sensitive to the former coupling while it becomes independent of the latter.
  • Publication
    Gravitational production of scalar dark matter
    (Springer, 2020-06-12) Ruiz Cembranos, José Alberto; Garay Elizondo, Luis Javier; Sánchez Velázquez, José Manuel
    We 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.
  • Publication
    Causal structure of accelerating black holes
    (Springer, 2022) Ruiz Cembranos, José Alberto; Garay Elizondo, Luis Javier; Ángel Ortega, Sergio
    Accelerating black holes are described by the so-called C-metric. In this work, we analyse the causal structure of such black holes by using null geodesics. We construct explicitly the relevant Penrose diagrams. First, we recover well-known results associated with the sub-accelerating black holes. Then, we extend the study to the super-accelerating case, in which an additional essential singularity appears. In addition, we consider accelerating black holes with negative masses. We show that they are equivalent to the geometry described by the black hole metric beyond conformal infinity. We compare our results with the Schwarzschild geometry to facilitate understanding and to highlight the interest of the new features.
  • Publication
    Unruh Effect without Thermality
    (American Physical Society, 2019-07-26) Carballo-Rubio, Raúl; Garay Elizondo, Luis Javier; Martín-Martínez, Eduardo; Ramón, José de
    We show that uniformly accelerated detectors can display genuinely thermal features even if the Kubo-Martin-Schwinger (KMS) condition fails to hold. These features include satisfying thermal detailed balance and having a Planckian response identical to cases in which the KMS condition is satisfied. In this context, we discuss that satisfying the KMS condition for accelerated trajectories is just sufficient but not necessary for the Unruh effect to be present in a given quantum field theory. Furthermore, we extract the necessary and sufficient conditions for the response function of an accelerated detector to be thermal in the infinitely adiabatic limit. This analysis provides new insight about the interplay between the KMS condition and the Unruh effect, and a solid framework in which the robustness of the Unruh effect against deformations of quantum field theories (perhaps Lorentz-violating) can be answered unambiguously. © 2019 American Physical Society.
  • Publication
    Scale holography
    (Springer, 2018-09-11) Ruiz Cembranos, José Alberto; Ciarreta, Salvador E.R.; Garay Elizondo, Luis Javier
    We present a new correspondence between a d-dimensional dynamical system and a family of higher-order derivative (d + 1)-dimensional systems. This new scaleholographic relation is built by the explicit introduction of a dimensionful constant which determines the size of the additional dimension. Scale holography is particularly useful for studying non-local theories, since the equivalent dual system on the higher dimensional manifold can be made to be local, as we illustrate with the specific examples of the p-adic string theory and the free particle.