Originally, the Unruh effect is considered in the Minkowski spacetime. That is, for a uniformly accelerated observer in the Minkowski spacetime, there will be an event horizon, and the observer will detect radiation from it. In this paper, we extend the Unruh effect to the Kruskal spacetime. After defining some special null hypersurface in the Kruskal spacetime, we find that it can be considere...

Some issues on the stability of black string or brane solutions are summarized briefly. The stability of dS/AdS-Schwarzschild black strings has been investigated. Interestingly, the AdS-Schwarzschild black strings turn out to be stable as the horizon size becomes larger than the AdS scale. It is also shown that BTZ black strings in four dimensions are stable regardless of the horizon size. Such...

Overview A linear predictive filter (LPF) is a short vector of coefficients whose inner product with a fragment of a time-sampled signal predicts one or more points of the 10 signal’s future within some error. When the prediction horizon is short, the filter is interpolative and constitutes a recognizer or classifier of the signal [3, 5]. When the prediction horizon is longer, the filter is ext...

We first show that the intrinsic, geometrical structure of a dynamical horizon is unique. A number of physically interesting constraints are then established on the location of trapped and marginally trapped surfaces in the vicinity of any dynamical horizon. These restrictions are used to prove several uniqueness theorems for dynamical horizons. Ramifications of some of these results to numeric...

In addition to briefly reviewing recent progress in studying black hole physics in string/M theory, we describe several robust features pertaining to spacetime physics that one can glean by studying quantum physics of black holes. In particular, we review ’t Hooft’s S-matrix ansatz which results in a noncommutative horizon. A recent construction of fuzzy AdS2 is emphasized, this is a nice toy m...

Any probe which crosses the horizon of a black hole should be absorbed. In M(atrix) theory, for 0-brane probes of Schwarzschild black holes, we argue that the relevant absorption mechanism is a tachyon instability which sets in at the horizon. We give qualitative arguments, and some quantitative large-N calculations, in support of this claim. The tachyon instability provides an attractive mecha...

The boundary of the region in spacetime containing future-trapped closed surfaces is considered. In asymptotically flat spacetimes, this boundary does not need to be the event horizon nor a dynamical/trapping horizon. Some properties of this boundary and its localization are analyzed, and illustrated with examples. In particular, fully explicit future-trapped compact surfaces penetrating into f...