Black hole radiation with high frequency dispersion

We consider one model of a black hole radiation, in which the equation of motion of a matter field is modified to cut off high frequency modes. The spectrum in the model has already been analytically derived in low frequency range, which has resulted in the Planckian distributin of the Hawking temperature. On the other hand, it has been numerically shown that its spectrum deviates from the thermal one in high frequency range. In this paper, we analytically derive the form of the deviation in the high frequency range. Our result can qualitatively explain the nature of the numerically calculated spectrum. The origin of the deviation is clarified by a simple discussion.Comment: 9 pages, 10 figures, submitted to Phys.Rev.

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Thesis (M.M.E.)--Boston Universit

Generalization of the model of Hawking radiation with modified high frequency dispersion relation

The Hawking radiation is one of the most interesting phenomena predicted by the theory of quantum field in curved space. The origin of Hawking radiation is closely related to the fact that a particle which marginally escapes from collapsing into a black hole is observed at the future infinity with infinitely large redshift. In other words, such a particle had a very high frequency when it was near the event horizon. Motivated by the possibility that the property of Hawking radiation may be altered by some unknowned physics which may exist beyond some critical scale, Unruh proposed a model which has higher order spatial derivative terms. In his model, the effects of unknown physics are modeled so as to be suppressed for the waves with a wavelength much longer than the critical scale, $k_0^{-1}$. Surprisingly, it was shown that the thermal spectrum is recovered for such modified models. To introduce such higher order spatial derivative terms, the Lorentz invariance must be violated because one special spatial direction needs to be chosen. In previous works, the rest frame of freely-falling observers was employed as this special reference frame. Here we give an extension by allowing a more general choice of the reference frame. Developing the method taken by Corley, % and especially focusing on subluminal case, we show that the resulting spectrum of created particles again becomes the thermal one at the Hawking temperature even if the choice of the reference frame is generalized. Using the technique of the matched asymptotic expansion, we also show that the correction to the thermal radiation stays of order $k_0^{-2}$ or smaller when the spectrum of radiated particle around its peak is concerned.Comment: 23 pages, 5 postscript figures, submitted to Physical Review

Origin of the Thermal Radiation in a Solid-State Analog of a Black-Hole

An effective black-hole-like horizon occurs, for electromagnetic waves in matter, at a surface of singular electric and magnetic permeabilities. In a physical dispersive medium this horizon disappears for wave numbers with $k>k_c$. Nevertheless, it is shown that Hawking radiation is still emitted if free field modes with $k>k_c$ are in their ground state.Comment: 13 Pages, 3 figures, Revtex with epsf macro

Controlling charge injection in organic field-effect transistors using self-assembled monolayers

We have studied charge injection across the metal/organic semiconductor interface in bottom-contact poly(3-hexylthiophene) (P3HT) field-effect transistors, with Au source and drain electrodes modified by self-assembled monolayers (SAMs) prior to active polymer deposition. By using the SAM to engineer the effective Au work function, we markedly affect the charge injection process. We systematically examine the contact resistivity and intrinsic channel mobility, and show that chemically increasing the injecting electrode work function significantly improves hole injection relative to untreated Au electrodes.Comment: 5 pages, 2 figures. Supplementary information available upon reques

Collapse of Kaluza-Klein Bubbles

Kaluza-Klein theory admits ``bubble" configurations, in which the circumference of the fifth dimension shrinks to zero on some compact surface. A three parameter family of such bubble initial data at a moment of time-symmetry (some including a magnetic field) has been found by Brill and Horowitz, generalizing the (zero-energy) ``Witten bubble" solution. Some of these data have negative total energy. We show here that all the negative energy bubble solutions start out expanding away from the moment of time symmetry, while the positive energy bubbles can start out either expanding or contracting. Thus it is unlikely that the negative energy bubbles would collapse and produce a naked singularity.Comment: 6 pages, plain LaTeX, UMDGR-94-08

Lattice Black Holes

We study the Hawking process on lattices falling into static black holes. The motivation is to understand how the outgoing modes and Hawking radiation can arise in a setting with a strict short distance cutoff in the free-fall frame. We employ two-dimensional free scalar field theory. For a falling lattice with a discrete time-translation symmetry we use analytical methods to establish that, for Killing frequency $\omega$ and surface gravity $\kappa$ satisfying $\kappa\ll\omega^{1/3}\ll 1$ in lattice units, the continuum Hawking spectrum is recovered. The low frequency outgoing modes arise from exotic ingoing modes with large proper wavevectors that "refract" off the horizon. In this model with time translation symmetry the proper lattice spacing goes to zero at spatial infinity. We also consider instead falling lattices whose proper lattice spacing is constant at infinity and therefore grows with time at any finite radius. This violation of time translation symmetry is visible only at wavelengths comparable to the lattice spacing, and it is responsible for transmuting ingoing high Killing frequency modes into low frequency outgoing modes.Comment: 26 pages, LaTeX, 2 figures included with psfig. Several improvements in the presentation. One figure added. Final version to appear in Phys.Rev.

Kappa - Poincare dispersion relations and the black hole radiation

Following the methods developed by Corley and Jacobson, we consider qualitatively the issue of Hawking radiation in the case when the dispersion relation is dictated by quantum kappa-Poincare algebra. This relation corresponds to field equations that are non-local in time, and, depending on the sign of the parameter kappa, to sub- or superluminal signal propagation. We also derive the conserved inner product, that can be used to count modes, and therefore to obtain the spectrum of black hole radiation in this case.Comment: 11 pages, 2 figure

Two Black Hole Holography, Lensing and Intensity

We numerically verify the analysis of the "expanding horizon" theory of Susskind in relation to the 't Hooft holographic conjecture. By using a numerical simulation to work out the image formed by two black holes upon a screen very far away, it is seen that it is impossible for a horizon to hide behind another. We also compute the intensity distribution of such an arrangement.Comment: 10 page