The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform

Orfeu Bertolami - One of the best experts on this subject based on the ideXlab platform.

  • MaVaNs in the generalized Chaplygin gas scenario: A Perturbative Approach for mass varying neutrinos coupled to the dark sector in the generalized Chaplygin gas scenario
    Journal of Physics: Conference Series, 2008
    Co-Authors: Alex E. Bernardini, Orfeu Bertolami
    Abstract:

    We suggest a Perturbative Approach for generic choices for the universe equation of state and introduce a novel framework for studying mass varying neutrinos (MaVaNs) coupled to the dark sector. For concreteness, we examine the coupling between neutrinos and the underlying scalar field associated with the generalized Chaplygin gas (GCG), a unification model for dark energy and dark matter. It is shown that the application of a Perturbative Approach to MaVaN mechanisms translates into a constraint on the coefficient of a linear perturbation, which depends on the ratio between a neutrino energy dependent term and scalar field potential terms. We quantify the effects on the MaVaN sector by considering neutrino masses generated by the seesaw mechanism. After setting the GCG parameters in agreement with general cosmological constraints, we find that the squared speed of sound in the neutrino-scalar GCG fluid is naturally positive. In this scenario, the model stability depends on previously set up parameters associated with the equation of state of the universe. Our results suggest that the GCG is a particularly suitable candidate for constructing a stable MaVaN scenario.

  • Perturbative Approach for mass varying neutrinos coupled to the dark sector in the generalized chaplygin gas scenario
    Physical Review D, 2008
    Co-Authors: Alex E. Bernardini, Orfeu Bertolami
    Abstract:

    We suggest a Perturbative Approach for generic choices for the universe equation of state and introduce a novel framework for studying mass varying neutrinos (MaVaN's) coupled to the dark sector. For concreteness, we examine the coupling between neutrinos and the underlying scalar field associated with the generalized Chaplygin gas (GCG), a unification model for dark energy and dark matter. It is shown that the application of a Perturbative Approach to MaVaN mechanisms translates into a constraint on the coefficient of a linear perturbation, which depends on the ratio between a neutrino energy dependent term and scalar field potential terms. We quantify the effects on the MaVaN sector by considering neutrino masses generated by the seesaw mechanism. After setting the GCG parameters in agreement with general cosmological constraints, we find that the squared speed of sound in the neutrino-scalar GCG fluid is naturally positive. In this scenario, the model stability depends on previously set up parameters associated with the equation of state of the universe. Our results suggest that the GCG is a particularly suitable candidate for constructing a stable MaVaN scenario.

  • Stationary condition in a Perturbative Approach for mass varying neutrinos
    Physics Letters B, 2008
    Co-Authors: Alex E. Bernardini, Orfeu Bertolami
    Abstract:

    A Perturbative Approach for arbitrary choices of the equation of state of the universe is introduced in order to treat scenarios for mass varying neutrinos (MaVaNs) coupled to the dark sector. The generalized criterion for the applicability of such an Approach is expressed through a constraint on the coefficient of the linear perturbation on the dark sector scalar field. This coefficient depends on the ratio between the variation of the neutrino energy and the scalar field potential. Upon certain conditions, the usual stationary condition found in the context of MaVaN models together with the Perturbative contribution can be employed to predict the dynamical evolution of the neutrino mass. Our results clearly indicate that the positiveness of the squared speed of sound of the coupled fluid and the model stability are not conditioned by the stationary condition.

Swapan K. Ghosh - One of the best experts on this subject based on the ideXlab platform.

  • Structure of an inhomogeneous fluid mixture: A new weighted density-functional theory within a Perturbative Approach
    The Journal of Chemical Physics, 2003
    Co-Authors: Niharendu Choudhury, Swapan K. Ghosh
    Abstract:

    A simple density-functional Approach is developed for an inhomogeneous fluid mixture where the functional Taylor expansion of the Perturbative Approach has been used along with a nonPerturbative weighted density prescription. The functional Taylor expansion of the one-particle direct correlation function (DCF) of the inhomogeneous fluid mixture is truncated at second order in density inhomogeneity and the effect of various higher-order terms is taken into account by evaluating the third-order DCF at an weighted density obtained by using a suitable weight function which obeys certain conditions in the homogeneous limit. The proposed Approach uses the two-particle DCFs of the corresponding uniform fluid mixture and their various density derivatives as inputs. The calculated numerical results for the density and concentration profiles of hard sphere mixtures near hard walls for different set of bulk parameters are shown to be in very good agreement with the available simulation data.

  • New Weighted Density Functional Theory Based on Perturbative Approach
    The Journal of Physical Chemistry B, 2003
    Co-Authors: Niharendu Choudhury, Swapan K. Ghosh
    Abstract:

    A new weighted density functional theory for inhomogeneous fluids is developed by combining the functional Taylor expansion of the Perturbative Approach with the nonPerturbative weighted density concept. In this Approach, the functional Taylor expansion of the one-particle direct correation function (DCF) is truncated at second order and the effect of a subset of the higher order terms is taken into account by evaluating the third-order DCF at a suitable weighted density, determined by demanding the fourth order DCF to be reproduced from the proposed expansion in the homogeneous limit. The present Approach uses as input the two-particle DCF of the corresponding uniform fluid along with an approximation to the three-particle DCF. The proposed theory is applied to hard sphere as well as Lennard-Jones fluids in confined geometries, and the calculated density profiles for both the systems are shown to be in very good overall agreement with the available simulation data.

François Vidal - One of the best experts on this subject based on the ideXlab platform.

  • A Perturbative Approach to self-phase modulation and self-steepening of short laser pulses propagating in nonlinear media
    Journal of Physics B: Atomic Molecular and Optical Physics, 2020
    Co-Authors: François Vidal
    Abstract:

    The solution of the wave equation in the envelope approximation with temporal corrections for a laser pulse propagating in a medium where the Kerr effect, field ionization, and associated absorption take place, is obtained through a first-order Perturbative Approach. The closed-form expressions so obtained clarify the influence of the various terms of the equation on the laser amplitude and on the frequency generation as a function of the retarded time. Furthermore, they allow extracting scaling parameters which size the nonlinear effects. The results are illustrated quantitatively on the case of a femtosecond pulse focused in the air with typical parameters.

Alex E. Bernardini - One of the best experts on this subject based on the ideXlab platform.

  • MaVaNs in the generalized Chaplygin gas scenario: A Perturbative Approach for mass varying neutrinos coupled to the dark sector in the generalized Chaplygin gas scenario
    Journal of Physics: Conference Series, 2008
    Co-Authors: Alex E. Bernardini, Orfeu Bertolami
    Abstract:

    We suggest a Perturbative Approach for generic choices for the universe equation of state and introduce a novel framework for studying mass varying neutrinos (MaVaNs) coupled to the dark sector. For concreteness, we examine the coupling between neutrinos and the underlying scalar field associated with the generalized Chaplygin gas (GCG), a unification model for dark energy and dark matter. It is shown that the application of a Perturbative Approach to MaVaN mechanisms translates into a constraint on the coefficient of a linear perturbation, which depends on the ratio between a neutrino energy dependent term and scalar field potential terms. We quantify the effects on the MaVaN sector by considering neutrino masses generated by the seesaw mechanism. After setting the GCG parameters in agreement with general cosmological constraints, we find that the squared speed of sound in the neutrino-scalar GCG fluid is naturally positive. In this scenario, the model stability depends on previously set up parameters associated with the equation of state of the universe. Our results suggest that the GCG is a particularly suitable candidate for constructing a stable MaVaN scenario.

  • Perturbative Approach for mass varying neutrinos coupled to the dark sector in the generalized chaplygin gas scenario
    Physical Review D, 2008
    Co-Authors: Alex E. Bernardini, Orfeu Bertolami
    Abstract:

    We suggest a Perturbative Approach for generic choices for the universe equation of state and introduce a novel framework for studying mass varying neutrinos (MaVaN's) coupled to the dark sector. For concreteness, we examine the coupling between neutrinos and the underlying scalar field associated with the generalized Chaplygin gas (GCG), a unification model for dark energy and dark matter. It is shown that the application of a Perturbative Approach to MaVaN mechanisms translates into a constraint on the coefficient of a linear perturbation, which depends on the ratio between a neutrino energy dependent term and scalar field potential terms. We quantify the effects on the MaVaN sector by considering neutrino masses generated by the seesaw mechanism. After setting the GCG parameters in agreement with general cosmological constraints, we find that the squared speed of sound in the neutrino-scalar GCG fluid is naturally positive. In this scenario, the model stability depends on previously set up parameters associated with the equation of state of the universe. Our results suggest that the GCG is a particularly suitable candidate for constructing a stable MaVaN scenario.

  • Stationary condition in a Perturbative Approach for mass varying neutrinos
    Physics Letters B, 2008
    Co-Authors: Alex E. Bernardini, Orfeu Bertolami
    Abstract:

    A Perturbative Approach for arbitrary choices of the equation of state of the universe is introduced in order to treat scenarios for mass varying neutrinos (MaVaNs) coupled to the dark sector. The generalized criterion for the applicability of such an Approach is expressed through a constraint on the coefficient of the linear perturbation on the dark sector scalar field. This coefficient depends on the ratio between the variation of the neutrino energy and the scalar field potential. Upon certain conditions, the usual stationary condition found in the context of MaVaN models together with the Perturbative contribution can be employed to predict the dynamical evolution of the neutrino mass. Our results clearly indicate that the positiveness of the squared speed of sound of the coupled fluid and the model stability are not conditioned by the stationary condition.

Niharendu Choudhury - One of the best experts on this subject based on the ideXlab platform.

  • Structure of an inhomogeneous fluid mixture: A new weighted density-functional theory within a Perturbative Approach
    The Journal of Chemical Physics, 2003
    Co-Authors: Niharendu Choudhury, Swapan K. Ghosh
    Abstract:

    A simple density-functional Approach is developed for an inhomogeneous fluid mixture where the functional Taylor expansion of the Perturbative Approach has been used along with a nonPerturbative weighted density prescription. The functional Taylor expansion of the one-particle direct correlation function (DCF) of the inhomogeneous fluid mixture is truncated at second order in density inhomogeneity and the effect of various higher-order terms is taken into account by evaluating the third-order DCF at an weighted density obtained by using a suitable weight function which obeys certain conditions in the homogeneous limit. The proposed Approach uses the two-particle DCFs of the corresponding uniform fluid mixture and their various density derivatives as inputs. The calculated numerical results for the density and concentration profiles of hard sphere mixtures near hard walls for different set of bulk parameters are shown to be in very good agreement with the available simulation data.

  • New Weighted Density Functional Theory Based on Perturbative Approach
    The Journal of Physical Chemistry B, 2003
    Co-Authors: Niharendu Choudhury, Swapan K. Ghosh
    Abstract:

    A new weighted density functional theory for inhomogeneous fluids is developed by combining the functional Taylor expansion of the Perturbative Approach with the nonPerturbative weighted density concept. In this Approach, the functional Taylor expansion of the one-particle direct correation function (DCF) is truncated at second order and the effect of a subset of the higher order terms is taken into account by evaluating the third-order DCF at a suitable weighted density, determined by demanding the fourth order DCF to be reproduced from the proposed expansion in the homogeneous limit. The present Approach uses as input the two-particle DCF of the corresponding uniform fluid along with an approximation to the three-particle DCF. The proposed theory is applied to hard sphere as well as Lennard-Jones fluids in confined geometries, and the calculated density profiles for both the systems are shown to be in very good overall agreement with the available simulation data.