TY - JOUR

T1 - Evidence for event horizons

T2 - 7th Black Holes Workshop

AU - Macedo, Caio F. B.

AU - Crispino, Luis C. B.

AU - Cardoso, Vitor

AU - Okawa, Hirotada

AU - Pani, Paolo

PY - 2015/8

Y1 - 2015/8

N2 - Gravitational compact astrophysical objects are excellent laboratories to test the strong field regime of theories of gravity. Among these compact objects, lies the ultracompact class: stellar structures that possess a light ring (circular null geodesic). Such ultracompact stars were presented in literature in the earlier solutions of general relativity, and some are claimed to be good candidates to the supermassive objects present at the center of galaxies. In this paper, we present evidences for the claim that compact objects with a light ring should be black holes, based on the existence of long-lived modes obtained through a first-order perturbation theory. These first-order long-lived modes can source nonlinear terms which could turn the star unstable. We show, in particular, a comparison between modes computed through an exact direct integration and through the WKB approximation. Moreover, we present the time evolution of wavepackets for different field configurations. We conjecture some possible outcomes of the nonlinear instability. The discussion presented in this work complements our previous paper [Phys. Rev. D 90 (2014) 044069].

AB - Gravitational compact astrophysical objects are excellent laboratories to test the strong field regime of theories of gravity. Among these compact objects, lies the ultracompact class: stellar structures that possess a light ring (circular null geodesic). Such ultracompact stars were presented in literature in the earlier solutions of general relativity, and some are claimed to be good candidates to the supermassive objects present at the center of galaxies. In this paper, we present evidences for the claim that compact objects with a light ring should be black holes, based on the existence of long-lived modes obtained through a first-order perturbation theory. These first-order long-lived modes can source nonlinear terms which could turn the star unstable. We show, in particular, a comparison between modes computed through an exact direct integration and through the WKB approximation. Moreover, we present the time evolution of wavepackets for different field configurations. We conjecture some possible outcomes of the nonlinear instability. The discussion presented in this work complements our previous paper [Phys. Rev. D 90 (2014) 044069].

KW - Event horizons

KW - long-lived modes

KW - ultracompact stars

KW - gravastars

KW - GRAVITATIONAL-WAVE DETECTORS

KW - STARS

U2 - 10.1142/S0218271815420237

DO - 10.1142/S0218271815420237

M3 - Journal article

VL - 24

JO - International Journal of Modern Physics D

JF - International Journal of Modern Physics D

SN - 0218-2718

IS - 9

M1 - 1542023

Y2 - 18 December 2014 through 19 December 2014

ER -