An ultrafast time-resolved magneto-optical pump probe is applied to study spin-relaxation processes in a ferromagnetic CoPt3 alloy film. Following spin-selective photoexcitation with circularly polarized femtosecond pulses, transient Kerr ellipticity tracks the evolution of the nonequilibrium spin system. We isolate two distinct processes: a subpicosecond component due to the relaxation of cohe...

In this Letter we consider the radial infall along the symmetry axis of an ultra-relativistic point particle into a rotating Kerr black hole. We use the Sasaki-Nakamura formalism to compute the waveform, energy spectra and total energy radiated during this process. We discuss possible connections between these results and the black holeblack hole collision at the speed of light process.

There are three regimes of gravitational-radiation-reaction-induced inspiral for a compact body with mass m , in a circular, equatorial orbit around a Kerr black hole with mass M@m: ~i! the adiabatic inspiral regime, in which the body gradually descends through a sequence of circular, geodesic orbits; ~ii! a transition regime, near the innermost stable circular orbit ~isco!; ~iii! the plunge re...

We show that using an adequate coordinate transformation the charged regular black hole solution given by Ayón-Beato and Garcia can be put in the Kerr-Schild form. Then we use this metric in Kerr-Schild Cartesian coordinates with a result given by Virbhadra and obtain the energy distribution associated with this.

Spatial dark optical solitons are localized light intensity dips in the infinite constant background [1–3]. Like their bright counterparts, they propagate preserving their spatial profile. This is a result of a balance between diffraction which tends to broaden their size and nonlinearity of the medium which counteracts this process. The existence of dark spatial solitons requires the nonlinear...

When solvinglinear scattering problems, one typically first solves for the impinging wave in the absence of obstacles. Then, using the linear superposition principle, the original problem is reduced to one which involves only the scattered wave (which is driven by the values of the impinging field at the surface of the obstacles). When the original domain is unbounded, special artificial bounda...

Peter Cramton is grateful to the National Science Foundation for its financial support. Suzi Kerr would like to thank Boaz Moselle, Rob Stavins, Ian Parry, Larry Goulder, and the members of the Greenhouse Gas Emissions Trading Braintrust, and gratefully acknowledges funding provided to her under a cooperative agreement between the US Environmental Protection Agency’s Office of Policy, Planning ...

The role of the parameter ‘a’ associated with the Kerr metric which represents the angular momentum per unit mass of a rotating massive object has been converted into determining the rotationally induced quadrapole electric field outside a rotating massive object with external dipole magnetic field. A comparison of the result with that of the Newtonian case implies that the parameter ‘a’ repres...

David M. Ramirez,1 Alejandro W. Rodriguez,2,3 Hila Hashemi,2 J. D. Joannopoulos,1 Marin Soljačić,1 and Steven G. Johnson2 1Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA 2Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA 3School of Science and Engineering, Harvard University, Cambridge, MA 02139, USA (Received 29 N...

Quasi-spherical light cones are lightlike hypersurfaces of the Kerr geometry that are asymptotic to Minkowski light cones at infinity. We develop the equations of these surfaces and examine their properties. In particular, we show that they are free of caustics for all positive values of the Kerr radial coordinate r. Useful applications include the propagation of high-frequency waves, the defin...