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Masashi Kimura - One of the best experts on this subject based on the ideXlab platform.

  • a simple test for stability of black hole by s Deformation
    Classical and Quantum Gravity, 2017
    Co-Authors: Masashi Kimura
    Abstract:

    We study a sufficient condition for proving the stability of a black hole when the master equation for linear perturbation takes the form of the Schrodinger equation. If the potential contains a small negative region, the S-Deformation method is usually used to show the non-existence of an unstable mode. However, in some cases, it is hard to find an appropriate Deformation Function analytically because the only way found so far to find it is by trial-and-error. In this paper, we show that it is easy to find a regular Deformation Function by numerically solving the differential equation such that the deformed potential vanishes everywhere, when the spacetime is stable. Even if the spacetime is almost marginally stable, our method still works. We also discuss a simple toy model which can be solved analytically, and show that the condition for the non-existence of a bound state is the same as that for the existence of a regular solution for the differential equation in our method. From these results, we conjecture that our criteria is also a necessary condition.

  • a simple test for stability of black hole by s Deformation
    arXiv: General Relativity and Quantum Cosmology, 2017
    Co-Authors: Masashi Kimura
    Abstract:

    We study a sufficient condition to prove the stability of a black hole when the master equation for linear perturbation takes the form of the Schr\"odinger equation. If the potential contains a small negative region, usually, the $S$-Deformation method was used to show the non-existence of unstable mode. However, in some cases, it is hard to find an appropriate Deformation Function analytically because the only way known so far to find it is a try-and-error approach. In this paper, we show that it is easy to find a regular Deformation Function by numerically solving the differential equation such that the deformed potential vanishes everywhere, when the spacetime is stable. Even if the spacetime is almost marginally stable, our method still works. We also discuss a simple toy model which can be solved analytically, and show the condition for the non-existence of a bound state is the same as that for the existence of a regular solution for the differential equation in our method. From these results, we conjecture that our criteria is also a necessary condition.

Mohammad Kazem Tavassoly - One of the best experts on this subject based on the ideXlab platform.

  • periodic behavior of collapse revival phenomenon in the full nonlinear interaction between a three level atom and a single mode field
    Annals of Physics, 2016
    Co-Authors: Mohammad Kazem Tavassoly, M Rastegarzadeh
    Abstract:

    Abstract In this paper based on a generalization of the Jaynes–Cummings model we solve the dynamical Hamiltonian describing the interaction between a ( Λ or V-type) three-level atom and a single-mode field in the “full nonlinear regime” and then the analytical form of state vector of the system is explicitly obtained. In this manner, we encountered with “intensity-dependent detuning” as well as “intensity-dependent atom–field coupling” in our two models. Via choosing an appropriate Deformation Function (which imposes nonlinearity to the system) we consider the influence of Kerr-like medium from which the resonance condition for a selected number of quanta is achieved (selective transition is occurred). Furthermore, by these considerations, we may find the optimum values for atom–field coupling constants which provide a regular periodic behavior of probability amplitudes for the two considered atomic systems. Moreover, to show this periodic time behavior, the temporal evolution of the probability of the allowed atomic transitions as well as the Mandel parameter (as a non-classical sign) is depicted for various circumstances. As is observed, complete revivals may appear in some particular situations.

  • Optimum coupling between a Ʌ-type three-level atom and a single-mode nonlinear field
    Optics and Photonics Society of Iran, 2015
    Co-Authors: Mojtaba Rastegarzadeh Bafroee, Mohammad Kazem Tavassoly
    Abstract:

    Based on the generalization of the Jaynes-Cummings model, we study the interaction between a Ʌ-type three-level atom and a single-mode radiation field in an intensity-dependent regime, in which the effect of Kerr-like medium is obtained by using an appropriate Deformation Function. Via the periodic condition, we will find an optimum value of coupling constant in resonance condition for which the atom suffers transitions with maximum (unit) probability, periodically.

M Rastegarzadeh - One of the best experts on this subject based on the ideXlab platform.

  • periodic behavior of collapse revival phenomenon in the full nonlinear interaction between a three level atom and a single mode field
    Annals of Physics, 2016
    Co-Authors: Mohammad Kazem Tavassoly, M Rastegarzadeh
    Abstract:

    Abstract In this paper based on a generalization of the Jaynes–Cummings model we solve the dynamical Hamiltonian describing the interaction between a ( Λ or V-type) three-level atom and a single-mode field in the “full nonlinear regime” and then the analytical form of state vector of the system is explicitly obtained. In this manner, we encountered with “intensity-dependent detuning” as well as “intensity-dependent atom–field coupling” in our two models. Via choosing an appropriate Deformation Function (which imposes nonlinearity to the system) we consider the influence of Kerr-like medium from which the resonance condition for a selected number of quanta is achieved (selective transition is occurred). Furthermore, by these considerations, we may find the optimum values for atom–field coupling constants which provide a regular periodic behavior of probability amplitudes for the two considered atomic systems. Moreover, to show this periodic time behavior, the temporal evolution of the probability of the allowed atomic transitions as well as the Mandel parameter (as a non-classical sign) is depicted for various circumstances. As is observed, complete revivals may appear in some particular situations.

Peter Guttorp - One of the best experts on this subject based on the ideXlab platform.

  • Variance modeling for nonstationary spatial processes with temporal replications
    Journal of Geophysical Research, 2003
    Co-Authors: Doris Damian, Paul D. Sampson, Peter Guttorp
    Abstract:

    [1] We have previously formulated a Bayesian approach to the Sampson and Guttorp model for the nonstationary correlation Function r(x, x′) of a Gaussian spatial process [Damian et al., 2001]. This model assumes that the nonstationarity can be encoded through a bijective space Deformation, f, that defines a new coordinate system in which the spatial correlation Function can be considered isotropic, namely r(x, x′) = ρ(∥f(x) − f(x′)∥), where ρ belongs to a known parametric family. We extend this model to incorporate spatial heterogeneity in site-specific temporal variances. In our Bayesian framework the variances are considered (hidden) realizations of another spatial process, which we model as log-Gaussian, with correlation structure expressed in terms of the same spatial Deformation Function underlying that of the observed process. We demonstrate the method in simulations and in an application.

L. Losano - One of the best experts on this subject based on the ideXlab platform.

  • Novel results for kinklike structures and their connections to quantum mechanics
    Annals of Physics, 2018
    Co-Authors: D. Bazeia, D.a. Ferreira, Elisama E. M. Lima, L. Losano
    Abstract:

    In this work we use the Deformation procedure and explore the route to obtain distinct field theory models that present similar stability potentials. Starting from systems that interact polynomially or hyperbolically, we use a Deformation Function which allows to construct other theories having the feature of giving rise to the same stability potentials. Such Deformation Function leads to smooth potentials according to a specific choice of a single parameter. Among the results, one shows that for models with asymmetric topological sectors, the appearance of a new stability potential is also possible.

  • Deformed defects for scalar fields with polynomial interactions
    Physical Review D, 2006
    Co-Authors: D. Bazeia, M. A. Gonzalez Leon, L. Losano, J. Mateos Guilarte
    Abstract:

    In this paper we use the Deformation procedure introduced in former work on deformed defects to investigate several new models for real scalar field. We introduce an interesting Deformation Function, from which we obtain two distinct families of models, labeled by the parameters that identify the Deformation Function. We investigate these models, which identify a broad class of polynomial interactions. We find exact solutions describing global defects, and we study the corresponding stability very carefully.