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Polettini Matteo - One of the best experts on this subject based on the ideXlab platform.

  • Equivalence principle and critical behaviour for nonequilibrium decay modes
    2014
    Co-Authors: Polettini Matteo
    Abstract:

    We generalize an orthonormality relation between decay eigenmodes of equilibrium systems to nonequilibrium markovian generators which commute with their time-reversal. Viewing such modes as tangent vectors to the manifold of statistical ensembles, we relate the result to the choice of a Coordinate Patch which makes the Fisher-Rao metric euclidean at the invariant state, realizing a sort of statistical equivalence principle. Finally, we classify nonequilibrium systems according to their spectrum, arguing that a degenerate Fisher matrix is a signature of the insurgence of a class of phase transitions between nonequilibrium regimes. We exhibit an order parameter with power-law critical decay and prove divergent correlations between suitable unbiased estimators.Comment: This paper has been withdrawn by the author. New vastly revised version of this paper: Fisher information of Markovian decay modes - Nonequilibrium equivalence principle, dynamical phase transitions and coarse graining, arXiv:1409.419

  • Fisher information of Markovian decay modes - Nonequilibrium equivalence principle, dynamical phase transitions and coarse graining
    'Springer Science and Business Media LLC', 2014
    Co-Authors: Polettini Matteo
    Abstract:

    We introduce the Fisher information in the basis of decay modes of Markovian dynamics, arguing that it encodes important information about the behavior of nonequilibrium systems. In particular we generalize an orthonormality relation between decay eigenmodes of detailed balanced systems to normal generators that commute with their time-reversal. Viewing such modes as tangent vectors to the manifold of statistical distributions, we relate the result to the choice of a Coordinate Patch that makes the Fisher-Rao metric Euclidean at the steady distribution, realizing a sort of statistical equivalence principle. We then classify nonequilibrium systems according to their spectrum, showing that a degenerate Fisher matrix is the signature of the insurgence of a class of dynamical phase transitions between nonequilibrium regimes, characterized by level crossing and power-law decay in time of suitable order parameters. An important consequence is that normal systems cannot manifest critical behavior. Finally, we study the Fisher matrix of systems with time-scale separation.Comment: 9 pages, 1 figure. Edited version of arXiv:1105.413

Matteo Polettini A - One of the best experts on this subject based on the ideXlab platform.

  • Fisher information of Markovian decay modes Nonequilibrium equivalence principle, dynamical phase transitions and coarse graining
    2016
    Co-Authors: Matteo Polettini A
    Abstract:

    Abstract. We introduce the Fisher information in the basis of decay modes of Markovian dynamics, arguing that it encodes important information about the behavior of nonequilibrium systems. In particular we generalize an orthonormality relation between decay eigenmodes of detailed balanced systems to normal generators that commute with their time-reversal. Viewing such modes as tangent vectors to the manifold of statistical distributions, we relate the result to the choice of a Coordinate Patch that makes the Fisher-Rao metric Euclidean at the steady distribution, realizing a sort of statistical equivalence principle. We then classify nonequilibrium systems according to their spectrum, showing that a degenerate Fisher matrix is the signature of the insurgence of a class of dynamical phase transitions between nonequilibrium regimes, characterized by level crossing and power-law decay in time of suitable order parameters. An important consequence is that normal systems cannot manifest critical behavior. Finally, we study the Fisher matrix of systems with time-scale separation.

Sperhake Ulrich - One of the best experts on this subject based on the ideXlab platform.

  • Tensor-multi-scalar theories: relativistic stars and 3 + 1 decomposition
    'IOP Publishing', 2015
    Co-Authors: Horbatsch Michael, Silva, Hector O, Gerosa Davide, Pani Paolo, Berti Emanuele, Gualtieri Leonardo, Sperhake Ulrich
    Abstract:

    Gravitational theories with multiple scalar fields coupled to the metric and each other—a natural extension of the well studied single-scalar-tensor theories—are interesting phenomenological frameworks to describe deviations from general relativity in the strong-field regime. In these theories, the N-tuple of scalar fields takes values in a Coordinate Patch of an N-dimensional Riemannian target-space manifold whose properties are poorly constrained by weak-field observations. Here we introduce for simplicity a non-trivial model with two scalar fields and a maximally symmetric target-space manifold. Within this model we present a preliminary investigation of spontaneous scalarization for relativistic, perfect fluid stellar models in spherical symmetry. We find that the scalarization threshold is determined by the eigenvalues of a symmetric scalar-matter coupling matrix, and that the properties of strongly scalarized stellar configurations additionally depend on the target-space curvature radius. In preparation for numerical relativity simulations, we also write down the 3 + 1 decomposition of the field equations for generic tensor-multi-scalar theories

  • Tensor-multi-scalar theories: relativistic stars and 3+1 decomposition
    'IOP Publishing', 2015
    Co-Authors: Horbatsch Michael, Silva, Hector O, Gerosa Davide, Pani Paolo, Berti Emanuele, Gualtieri Leonardo, Sperhake Ulrich
    Abstract:

    Gravitational theories with multiple scalar fields coupled to the metric and each other --- a natural extension of the well studied single-scalar-tensor theories --- are interesting phenomenological frameworks to describe deviations from general relativity in the strong-field regime. In these theories, the $N$-tuple of scalar fields takes values in a Coordinate Patch of an $N$-dimensional Riemannian target-space manifold whose properties are poorly constrained by weak-field observations. Here we introduce for simplicity a non-trivial model with two scalar fields and a maximally symmetric target-space manifold. Within this model we present a preliminary investigation of spontaneous scalarization for relativistic, perfect fluid stellar models in spherical symmetry. We find that the scalarization threshold is determined by the eigenvalues of a symmetric scalar-matter coupling matrix, and that the properties of strongly scalarized stellar configurations additionally depend on the target-space curvature radius. In preparation for numerical relativity simulations, we also write down the $3+1$ decomposition of the field equations for generic tensor-multi-scalar theories.Comment: 32 pages, 8 figures, 1 table, invited contribution to the Classical and Quantum Gravity Focus Issue "Black holes and fundamental fields". v3: version in press in CQG, with various improvements in response to the referees' comments. In particular, the 3+1 decomposition now allows for matte

Kim Jung-wook - One of the best experts on this subject based on the ideXlab platform.

  • Explicit reconstruction of the entanglement wedge
    'Springer Science and Business Media LLC', 2017
    Co-Authors: Kim Jung-wook
    Abstract:

    The problem of how the boundary encodes the bulk in AdS/CFT is still a subject of study today. One of the major issues that needs more elucidation is the problem of subregion duality; what information of the bulk a given boundary subregion encodes. Although the proof given by Dong, Harlow, and Wall states that the entanglement wedge of the bulk should be encoded in boundary subregions, no explicit procedure for reconstructing the entanglement wedge was given so far. In this paper, mode sum approach to obtaining smearing functions for a single bulk scalar is generalised to include bulk reconstruction in the entanglement wedge of boundary subregions. It is generally expectated that solutions to the wave equation on a complicated Coordinate Patch are needed, but this hard problem has been transferred to a less hard but tractable problem of matrix inversion.Comment: version accepted by JHEP; added references and discussions on covarianc

  • Explicit reconstruction of the entanglement wedge
    2016
    Co-Authors: Kim Jung-wook
    Abstract:

    The problem of bulk locality, or how the boundary encodes the bulk in AdS/CFT, is still a subject of study today. One of the major issues that needs more elucidation is the problem of subregion duality; what information of the bulk a given boundary subregion encodes. Although proofs given by two teams of researchers, Dong, Harlow, and Wall and Bao, and Kim, state that the entanglement wedge of the bulk should be reconstructible from boudnary subregions, no explicit procedure for reconstructing the entanglement wedge was as of yet given. In this paper, mode sum approach to obtaining smearing functions is generalised to include bulk reconstruction in the entanglement wedge of boundary subregions. It is generally expectated that solutions to the wave equation on a complicated Coordinate Patch are needed, but this hard problem has been transferred to a less hard but tractable problem of matrix inversion

Matteo Polettini - One of the best experts on this subject based on the ideXlab platform.

  • Fisher information of Markovian decay modes
    'Springer Science and Business Media LLC', 2014
    Co-Authors: Matteo Polettini
    Abstract:

    We introduce the Fisher information in the basis of decay modes of Markovian dynamics, arguing that it encodes important information about the behavior of nonequilibrium systems. In particular we generalize an orthonormality relation between decay eigenmodes of detailed balanced systems to normal generators that commute with their time-reversal. Viewing such modes as tangent vectors to the manifold of statistical distributions, we relate the result to the choice of a Coordinate Patch that makes the Fisher-Rao metric Euclidean at the steady distribution, realizing a sort of statistical equivalence principle. We then classify nonequilibrium systems according to their spectrum, showing that a degenerate Fisher matrix is the signature of the insurgence of a class of dynamical phase transitions between nonequilibrium regimes, characterized by level crossing and power-law decay in time of suitable order parameters. An important consequence is that normal systems cannot manifest critical behavior. Finally, we study the Fisher matrix of systems with time-scale separation