Quasi-normale Moden von rotierenden Schwarzen Löchern in alternativen Gravitationstheorien
Zusammenfassung der Projektergebnisse
The project was inspired by the tremendous progress, that was achieved in recent years in astrophysical observations of black holes and in the detection of gravitational waves from the inspiral, merger and ringdown of black hole and neutron star binary systems. After a merger the newly formed highly excited compact object emits during its ringdown to a stationary state a characteristic set of gravitational waves, called quasinormal modes. By analyzing these quasinormal modes one can learn about the properties of the object as well as about the gravitational theory governing the process. While General Relativity is in agreement with all current observations, it is expected to be superseded by a more fundamental theory of gravity. This has given rise to the theoretical construction of a large variety of alternative gravity theories. These theories often invoke further degrees of freedom as, for instance, scalar fields. Since it is most important to obtain clues from observations on these theories, a study of their predictions for observable properties is called for. This project has developed an appropriate set of tools to calculate the quasinormal modes of highly compact objects like black holes and neutron stars in alternative theories of gravity, when these objects are rotating, which they typically do. The rotating Kerr black holes of General Relativity have very special properties, which allowed to obtain their quasinormal mode spectrum already long ago. However, for more general spacetimes new tools were needed. We have developed a scheme, where we first consider the general set of perturbations on a rotating background solution, that is normally only known numerically. This leads to a system of coupled partial differential equations, that is numerically solved with a spectral method. We have tested this method for Kerr black holes, where the spectrum of quasinormal modes is well-known. We have applied the method to the rotating black holes of an alternative theory called Einsteindilaton-Gauss-Bonnet theory. This theory represents an effective gravity theory with higher order curvature corrections and an additional scalar degree of freedom. We have obtained the spectrum of the fundamental quasinormal modes in almost the full domain of existence of the rotating black holes. These results include also the slowly rotating limit. Employing neither perturbation theory in the angular momentum nor in the coupling constant of the gravitational theory, these results represent the first exact set of quasinormal modes of rapidly rotating black holes in an alternative theory of gravity. Our new tools are now ready to be applied to calculate the quasinormal modes of rotating black holes in various other gravity theories. However, they can also be applied to obtain the quasinormal modes of rotating neutron stars in General Relativity and alternative gravity theories. Likewise, they can be applied to other compact objects. We have already applied these tools to study the quasinormal modes of rotating Ellis-Bronnikov wormholes, where we observed the rotational breaking of the threefold isospectrality of static symmetric wormholes. We are currently applying these tools to study the unstable modes of these wormholes, where our slow rotation analysis yielded strong indications, that rotation would stabilize the wormholes. Furthermore, these tools are also applicable to other types of compact objects like boson stars.
Projektbezogene Publikationen (Auswahl)
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Quasinormal modes of slowly rotating Kerr-Newman black holes using the double series method. Physical Review D, 107(8).
Blázquez-Salcedo, Jose Luis & Khoo, Fech Scen
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Are slowly rotating Ellis-Bronnikov wormholes stable?. Physics Letters B, 848, 138349.
Azad, Bahareh; Blázquez-Salcedo, Jose Luis; Khoo, Fech Scen & Kunz, Jutta
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Quasinormal modes of Kerr black holes using a spectral decomposition of the metric perturbations. Physical Review D, 109(6).
Blázquez-Salcedo, Jose Luis; Khoo, Fech Scen; Kunz, Jutta & González-Romero, Luis Manuel
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Quasinormal modes of rapidly rotating Ellis-Bronnikov wormholes. Physical Review D, 109(8).
Khoo, Fech Scen; Azad, Bahareh; Blázquez-Salcedo, Jose Luis; González-Romero, Luis Manuel; Kleihaus, Burkhard; Kunz, Jutta & Navarro-Lérida, Francisco
