The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform

W. Simon - One of the best experts on this subject based on the ideXlab platform.

  • On the Spherical Symmetry of static perfect fluids in general relativity
    Letters in Mathematical Physics, 1991
    Co-Authors: R. Beig, W. Simon
    Abstract:

    We present a theorem which establishes uniqueness, in particular Spherical Symmetry, of a wide class of general relativistic, static perfect-fluid models provided there exists a Spherically symmetric model with the same equation of state and surface potential. The method of proof, which is inspired by recent work of Masood-ul-Alam, is illustrated by demonstrating uniqueness of a class of solutions due to Buchdahl which correspond to an extreme case of the inequality on the equation of state required by our theorem.

A. K. M. Masood-ul-alam - One of the best experts on this subject based on the ideXlab platform.

  • On the Spherical Symmetry of static stellar models
    Communications in Mathematical Physics, 1994
    Co-Authors: Lee Lindblom, A. K. M. Masood-ul-alam
    Abstract:

    This paper completes the proof of the necessity of Spherical Symmetry in the static general-relativistic stellar models that have equations of state satisfying certain inequalities. The technical assumption — that there exists a “reference Spherical stellar model” — that was essential in the previous discussions of this problem is removed. This paper also extends beyond previous discussions the class of equations of state included in the proof. The analysis of the equations for Spherical stellar models, used here to demonstrate the existence of a “reference Spherical model,” may also be of independent interest.

Ludwig Baringhaus - One of the best experts on this subject based on the ideXlab platform.

  • Testing for Spherical Symmetry of a Multivariate Distribution
    The Annals of Statistics, 1991
    Co-Authors: Ludwig Baringhaus
    Abstract:

    Rotationally invariant tests based on test statistics of the von Mises type are proposed under the hypothesis of Spherical Symmetry of a multivariate distribution. The tests are distribution-free when the hypothesis of Spherical Symmetry is true. The asymptotic distribution of the test statistics are derived under the null hypothesis and under any fixed alternative. A simple criterion for consistency is given. The results are illustrated by numerous examples of test statistics which give rise to tests being consistent against all alternatives.

R. Beig - One of the best experts on this subject based on the ideXlab platform.

  • On the Spherical Symmetry of static perfect fluids in general relativity
    Letters in Mathematical Physics, 1991
    Co-Authors: R. Beig, W. Simon
    Abstract:

    We present a theorem which establishes uniqueness, in particular Spherical Symmetry, of a wide class of general relativistic, static perfect-fluid models provided there exists a Spherically symmetric model with the same equation of state and surface potential. The method of proof, which is inspired by recent work of Masood-ul-Alam, is illustrated by demonstrating uniqueness of a class of solutions due to Buchdahl which correspond to an extreme case of the inequality on the equation of state required by our theorem.

Valerio Faraoni - One of the best experts on this subject based on the ideXlab platform.

  • Turnaround physics beyond Spherical Symmetry
    Physical Review D, 2021
    Co-Authors: Andrea Giusti, Valerio Faraoni
    Abstract:

    The concept of turnaround surface in an accelerating universe is generalized to arbitrarily large deviations from Spherical Symmetry, to close the gap between the idealized theoretical literature and the real world observed by astronomers. As an analytical application, the characterization of turnaround surface is applied to small deviations from Spherical Symmetry, recovering a previous result while extending it to scalar-tensor gravity.

  • Foliation dependence of black hole apparent horizons in Spherical Symmetry
    Phys.Rev.D, 2017
    Co-Authors: Valerio Faraoni, George F. R. Ellis, Javad T. Firouzjaee, Alexis Helou, Ilia Musco
    Abstract:

    Numerical studies of gravitational collapse to black holes make use of apparent horizons, which are intrinsically foliation dependent. We expose the problem and discuss possible solutions using the Hawking-Hayward quasilocal mass. In Spherical Symmetry, we present a physically sensible approach to the problem by restricting to Spherically symmetric spacetime slicings. In Spherical Symmetry, the apparent horizons enjoy a restricted gauge independence in any Spherically symmetric foliation, but physical quantities associated with them, such as surface gravity and temperature, are fully gauge dependent. The widely used comoving and Kodama foliations, which are of particular interest, are discussed in detail as examples.