HLADÍK, Jan, Nelson Camilo POSADA AGUIRRE and Zdeněk STUCHLÍK. Radial instability of trapping polytropic spheres. International Journal of Modern Physics D. 2020, vol. 29, No 5, p. "2050030-1"-"2050030-20", 20 pp. ISSN 0218-2718. Available from: https://dx.doi.org/10.1142/S0218271820500303.
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Basic information
Original name Radial instability of trapping polytropic spheres
Authors HLADÍK, Jan (203 Czech Republic, guarantor, belonging to the institution), Nelson Camilo POSADA AGUIRRE (170 Colombia, belonging to the institution) and Zdeněk STUCHLÍK (203 Czech Republic, belonging to the institution).
Edition International Journal of Modern Physics D, 2020, 0218-2718.
Other information
Original language English
Type of outcome Article in a journal
Field of Study 10308 Astronomy
Country of publisher Singapore
Confidentiality degree is not subject to a state or trade secret
WWW WWW
RIV identification code RIV/47813059:19630/20:A0000041
Organization unit Institute of physics in Opava
Doi http://dx.doi.org/10.1142/S0218271820500303
UT WoS 000531817300002
Keywords in English radial stability; polytropic spheres; Sturm-Liouville equation
Tags FÚ, FÚ2020
Tags International impact, Reviewed
Changed by Changed by: RNDr. Jan Hladík, Ph.D., učo 25379. Changed: 16/3/2021 14:52.
Abstract
We complete the stability study of general-relativistic spherically symmetric polytropic perfect fluid spheres, concentrating our attention on the newly discovered polytropes containing region of trapped null geodesics. We compare the methods of treating the dynamical stability based on the equation governing infinitesimal radial pulsations of the polytropes and the related Sturm-Liouville eigenvalue equation for the eigenmodes governing the pulsations, to the methods of stability analysis based on the energetic considerations. Both methods are applied to determine the stability of the polytropes governed by the polytropic index n in the whole range 0 < n < 5, and the relativistic parameter sigma given by the ratio of the central pressure and energy density, restricted by the causality limit. The critical values of the adiabatic index for stability are determined, together with the critical values of the relativistic parameter sigma. For the dynamical approach, we implemented a numerical method which is independent on the choice of the trial function, and compare its results with the standard trial function approach. We found that the energetic and dynamic method give nearly the same critical values of sigma. We found that all the configurations having trapped null geodesics are unstable according to both methods.
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