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374 papers
Universal Relations Meet Causality: Bounding the Dynamical Love Number of Neutron Stars
Alex Kehagias, Antonio Riotto
The frequency-dependent tidal response of a neutron star is constrained by causality, reality and passivity, which turn a suitably rescaled response into a holomorphic self-map of…
Scalar Gauss-Bonnet Wormholes and the Imaginary Distance Bound
Alex Kehagias, Antonio Riotto
We study symmetric Euclidean wormholes in four-dimensional gravity with a massless scalar linearly coupled to the Gauss-Bonnet invariant. At nonzero coupling, the Einstein w…
On the Modes at the Schwarzschild Black Hole Horizon
Dimitrios Giataganas, Alex Kehagias, Antonio Riotto
We discuss the origin of the modes appearing at the Schwarzschild black hole horizon and decaying at integer multiples of the surface gravity. We argue that no excitations generate…
The Schwarzschild Black Hole in an External Gravitational Tidal Field: the Quasinormal Spectrum
Dimitrios Giataganas, Alex Kehagias, Antonio Riotto
A black hole need not ring down in isolation, since a nearby companion can subject it to an external gravitational tide. We calculate how a quadrupole tide modifies the Schwarzschi…
A Bound on the Dynamical Love Number
Alex Kehagias, Antonio Riotto
The tidal deformability of a compact object is encoded in a single function of frequency, the retarded Green's function relating the induced multipole to the applied tide. Causalit…
Radial Mirror Scattering and the QNM Convergence Region
Alex Kehagias, Antonio Riotto
We revisit the convergence region of the quasinormal modes expansion of Schwarzschild retarded Green functions from a radial scattering viewpoint. The tortoise coordinate admits a…