Introduces Debye series and Debye-QNMs to decompose waveforms from Schwarzschild-star models, achieving early-time convergence and organizing ringdown plus echo packets into individual propagation channels.
Exotic Compact Objects and How to Quench their Ergoregion Instability
4 Pith papers cite this work. Polarity classification is still indexing.
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abstract
Gravitational-wave astronomy can give us access to the structure of black holes, potentially probing microscopic or even Planckian corrections at the horizon scale, as those predicted by some quantum-gravity models of exotic compact objects. A generic feature of these models is the replacement of the horizon by a reflective surface. Objects with these properties are prone to the so-called ergoregion instability when they spin sufficiently fast. We investigate in detail a simple model consisting of scalar perturbations of a Kerr geometry with a reflective surface near the horizon. The instability depends on the spin, on the compactness, and on the reflectivity at the surface. The instability time scale increases only logarithmically in the black-hole limit and, for a perfectly reflecting object, this is not enough to prevent the instability from occurring on dynamical time scales. However, we find that an absorption rate at the surface as small as 0.4% (reflectivity coefficient as large as $|{\cal R}|^2=0.996$) is sufficient to quench the instability completely. Our results suggest that exotic compact objects are not necessarily ruled out by the ergoregion instability.
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Excitation factors of long-lived quasinormal modes in horizonless compact objects scale with their small imaginary frequency, suppressing early contributions and producing a hierarchy where prompt ringdown uses ordinary modes and late echoes use cavity modes.
In quasi-topological gravity, neutron stars can surpass black-hole compactness with universal high-density behavior and theory corrections that stabilize radially unstable configurations from general relativity.
High-frequency quasi-reflectionless scattering modes in the greybody factors of ultracompact horizonless objects are responsible for echoes in the time-domain response.
citing papers explorer
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Ringdown and echoes from compact objects: Debye series and Debye quasinormal modes
Introduces Debye series and Debye-QNMs to decompose waveforms from Schwarzschild-star models, achieving early-time convergence and organizing ringdown plus echo packets into individual propagation channels.
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Excitation factors for horizonless compact objects: long-lived modes, echoes, and greybody factors
Excitation factors of long-lived quasinormal modes in horizonless compact objects scale with their small imaginary frequency, suppressing early contributions and producing a hierarchy where prompt ringdown uses ordinary modes and late echoes use cavity modes.
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Neutron stars more compact than black holes in quasi-topological gravity: Equilibrium configurations and radial stability
In quasi-topological gravity, neutron stars can surpass black-hole compactness with universal high-density behavior and theory corrections that stabilize radially unstable configurations from general relativity.
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Greybody factors, reflectionless scattering modes, and echoes of ultracompact horizonless objects
High-frequency quasi-reflectionless scattering modes in the greybody factors of ultracompact horizonless objects are responsible for echoes in the time-domain response.