Encontrados 14 documentos, a visualizar página 1 de 2
Hawking radiation for a Proca field in D dimensions
Herdeiro, Carlos; Sampaio, Marco O. P.; Wang, MengjieWe study the wave equation of a massive vector boson in the background of a D-dimensional Schwarzschild black hole. The mass term introduces a coupling between two physical degrees of freedom of the field, and we solve the resulting system of ordinary differential equations numerically, without decoupling. We show how to define decoupled transmission factors from an S matrix and compute them for various modes, ...
Mathisson's helical motions for a spinning particle: Are they unphysical?
Costa, L. Filipe; Herdeiro, Carlos; Natario, Jose; Zilhão, MiguelIt has been asserted in the literature that Mathisson's helical motions are unphysical, with the argument that their radius can be arbitrarily large. We revisit Mathisson's helical motions of a free spinning particle, and observe that such statement is unfounded. Their radius is finite and confined to the disk of centroids. We argue that the helical motions are perfectly valid and physically equivalent descript...
Radiation from a D-dimensional collision of shock waves: first order perturbati...
Herdeiro, Carlos; Sampaio, Marco O. P.; Rebelo, CarmenWe study the spacetime obtained by superimposing two equal Aichelburg-Sexl shock waves in D dimensions traveling, head-on, in opposite directions. Considering the collision in a boosted frame, one shock becomes stronger than the other, and a perturbative framework to compute the metric in the future of the collision is setup. The geometry is given, in first order perturbation theory, as an integral solution, in...
n-DBI gravity
Herdeiro, Carlos; Hirano, Shinji; Sato, Yukin-DBI gravity is a gravitational theory introduced in [C. Herdeiro and S. Hirano, arXiv: 1109.1468.], motivated by Dirac-Born-Infeld type conformal scalar theory and designed to yield noneternal inflation spontaneously. It contains a foliation structure provided by an everywhere timelike vector field n, which couples to the gravitational sector of the theory, but decouples in the small curvature limit. We show ...
Higher-dimensional puncture initial data
Zilhão, Miguel; Ansorg, Marcus; Cardoso, Vitor; Gualtieri, Leonardo; Herdeiro, Carlos; Sperhake, Ulrich; Witek, HelviWe calculate puncture initial data, corresponding to single and binary black holes with linear momenta, which solve the constraint equations of D-dimensional vacuum gravity. The data are generated by a modification of the pseudospectral code presented in [M. Ansorg, B. Bruegmann, and W. Tichy, Phys. Rev. D 70, 064011 (2004).] and made available as the TWOPUNCTURES thorn inside the CACTUS computational toolkit. ...
The Casimir spectrum revisited
Herdeiro, Carlos A. R.; Sampaio, Marco O. P.; Santos, Jaime E.We examine the mathematical and physical significance of the spectral density sigma(omega) introduced by Ford [Phys. Rev. D 38, 528 (1988)], defining the contribution of each frequency to the renormalised energy density of a quantum field. Firstly, by considering a simple example, we argue that sigma(omega) is well defined, in the sense of being regulator independent, despite an apparently regulator dependent d...
Head-on collisions of unequal mass black holes in D=5 dimensions
Witek, Helvi; Cardoso, Vitor; Gualtieri, Leonardo; Herdeiro, Carlos; Sperhake, Ulrich; Zilhao, MiguelWe study head-on collisions of unequal mass black hole binaries in D = 5 spacetime dimensions, with mass ratios between 1:1 and 1:4. Information about gravitational radiation is extracted by using the Kodama-Ishibashi gauge-invariant formalism and details of the apparent horizon of the final black hole. We present waveforms, total integrated energy and momentum for this process. Our results show surprisingly go...
Electromagnetic and Gravitational Invariants
Costa, L. Filipe O.; Herdeiro, Carlos A. R.; Wylleman, LodeThe curvature invariants have been subject of recent interest in the context of the experimental detection of the gravitomagnetic field, namely due to the debate concerning the notions of "extrinsic" and "intrinsic" gravitomagnetism. In this work we explore the physical meaning of the curvature invariants, dissecting their relationship with the gravitomagnetic effects.
Numerical Relativity in D dimensional space-times: Collisions of unequal mass b...
Witek, Helvi; Cardoso, Vitor; Gualtieri, Leonardo; Herdeiro, Carlos; Sperhake, Ulrich; Zilhão, MiguelWe present unequal mass head-on collisions of black holes in D = 5 dimensional space-times. We have simulated BH systems with mass ratios q = 1,1/2,1/3,1/4. We extract the total energy radiated throughout the collision and compute the linear momentum flux and the recoil velocity of the final black hole. The numerical results show very good agreement with point particle calculations when extrapolated to this limit.
Simulations of black holes in compactified spacetimes
Zilhão, Miguel; Cardoso, Vitor; Gualtieri, Leonardo; Herdeiro, Carlos; Nerozzi, Andrea; Sperhake, Ulrich; Witek, HelviFrom the gauge/gravity duality to braneworld scenarios, black holes in compactified spacetimes play an important role in fundamental physics. Our current understanding of black hole solutions and their dynamics in such spacetimes is rather poor because analytical tools are capable of handling a limited class of idealized scenarios, only. Breakthroughs in numerical relativity in recent years, however, have opene...
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