Persona:
Alvarellos Bermejo, José Enrique

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0000-0003-2184-2787
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Alvarellos Bermejo
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José Enrique
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Fecha de finalización: 2019 × Fecha de inicio: 2018 ×

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Mostrando 1 - 3 de 3
  • Miniatura
    Publicación
    Resonant behavior and unpredictability in forced chaotic scattering
    (American Chemical Society, 2018-12-10) Nieto, Alexandre R.; Seoane, Jesús M.; Sanjuán, Miguel A. F.; Alvarellos Bermejo, José Enrique
    Chaotic scattering in open Hamiltonian systems is a topic of fundamental interest in physics, which has been mainly studied in the purely conservative case. However, the effect of weak perturbations in this kind of system has been an important focus of interest in the past decade. In a previous work, the authors studied the effects of a periodic forcing in the decay law of the survival probability, and they characterized the global properties of escape dynamics. In the present paper, we add two important issues in the effects of periodic forcing: the fractal dimension of the set of singularities in the scattering function and the unpredictability of the exit basins, which is estimated by using the concept of basin entropy. Both the fractal dimension and the basin entropy exhibit a resonant-like decrease as the forcing frequency increases. We provide a theoretical reasoning which could justify this decreasing in the fractality near the main resonant frequency that appears for ω ≈ 1. We attribute the decrease in the basin entropy to the reduction of the area occupied by the Kolmogorov-Arnold-Moser (KAM) islands and the basin boundaries when the frequency is close to the resonance. On the other hand, the decay rate of the exponential decay law shows a minimum value of the amplitude, Ac, which reflects the complete destruction of the KAM islands in the resonance. Finally, we have found the existence ofWada basins for a wide range of values of the frequency and the forcing amplitude. We expect that this work could be potentially useful in research fields related to chaotic Hamiltonian pumps and oscillations in chemical reactions and companion galaxies, among others.
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    Publicación
    Entanglement detachment in fermionic systems
    (Springer, 2018-11-27) Santos, Hernán; Alvarellos Bermejo, José Enrique; Rodríguez Laguna, Javier
    This article introduces and discusses the concept of entanglement detachment. Under some circumstances, enlarging a few couplings of a Hamiltonian can effectively detach a (possibly disjoint) block within the ground state. This detachment is characterized by a sharp decrease in the entanglement entropy between block and environment, and leads to an increase of the internal correlations between the (possibly distant) sites of the block. We provide some examples of this detachment in free fermionic systems. The first example is an edge-dimerized chain, where the second and penultimate hoppings are increased. In that case, the two extreme sites constitute a block which disentangles from the rest of the chain. Further examples are given by (a) a superlattice which can be detached from a 1D chain, and (b) a star-graph, where the extreme sites can be detached or not depending on the presence of an external magnetic field, in analogy with the Aharonov-Bohm effect. We characterize these detached blocks by their reduced matrices, specially through their entanglement spectrum and entanglement Hamiltonian.
  • Miniatura
    Publicación
    Engineering large end-to-end correlations in finite fermionic chains
    (American Physical Society., 2018-12-14) Santos, Hernán; Alvarellos Bermejo, José Enrique; Rodríguez Laguna, Javier
    We explore deformations of finite chains of noninteracting fermions at half-filling which give rise to large correlations between their extremes. After a detailed study of the Su-Schrieffer-Heeger model, the tradeoff curve between end-to-end correlations and the energy gap of the chains is obtained using machine-learning techniques, paying special attention to the scaling behavior with the chain length.We find that edge-dimerized chains, where the second and penultimate hoppings are reinforced, are very often close to the optimal configurations. Our results allow us to conjecture that, given a fixed gap, the maximal attainable correlation falls exponentially with the system size. Study of the entanglement entropy and contour of the optimal configurations suggest that the bulk entanglement pattern is minimally modified from the clean case.