Vanishing Hawking Radiation from a Uniformly Accelerated Black Hole

We consider quantum fields around uniformly accelerated black holes. At a particular value of the acceleration, the Bogolubov transformation which would be responsible for the late-time Hawking radiation, is found to be trivial. When this happens, Hawking's thermal radiation, Doppler-shifted or not, is absent to the asymptotic inertial observers despite the nonzero Hawking temperature, while the co-moving observers find the black hole radiance exactly balanced by the acceleration heat bath. After a brief comparison to the classical system of a uniformly accelerated charge, we close with two important comments. (Phys. Rev. Lett. 75 (1995) 382)Comment: LaTeX, 10pages, 2 figures (a typo in Eq.(3) corrected; minor revisions to accomodate the length limitation of the journal

The Schwinger Mechanism, the Unruh Effect and the Production of Accelerated Black Holes

We compute the corrections to the transition amplitudes of an accelerated Unruh ``box'' that arise when the accelerated box is replaced by a ``two level ion'' immersed in a constant electric field and treated in second quantization. There are two kinds of corrections, those due to recoil effects induced by the momentum transfers and those due to pair creation. Taken together, these corrections show that there is a direct relationship between pair creation amplitudes described by the Heisenberg-Euler-Schwinger mechanism and the Unruh effect, i.e. the thermalisation of accelerated systems at temperature $a/ 2 \pi$ where $a$ is the acceleration. In particular, there is a thermodynamical consistency between both effects whose origin is that the euclidean action governing pair creation rates acts as an entropy in delivering the Unruh temperature. Upon considering pair creation of charged black holes in an electric field, these relationships explain why black holes are created from vacuum in thermal equilibrium, i.e. with their Hawking temperature equal to their Unruh temperature.Comment: Revised version: expanded introduction and discussion of pair creation of black holes, 2figures added, 22 pages, Late

Effective Hamiltonian Approach to the Master Equation

A method of exactly solving the master equation is presented in this letter. The explicit form of the solution is determined by the time evolution of a composite system including an auxiliary system and the open system in question. The effective Hamiltonian governing the time evolution of the composed system are derived from the master equation. Two examples, the dissipative two-level system and the damped harmonic oscillator, are presented to illustrate the solving procedure. PACS number(s): 05.30.-d, 05.40.+j, 42.50.CtComment: 4 pages, no figure

Pair production of neutral Higgs bosons at the CERN Large Hadron Collider

We study the hadroproduction of two neutral Higgs bosons in the minimal supersymmetric extension of the standard model, which provides a handle on the trilinear Higgs couplings. We include the contributions from quark-antiquark annihilation at the tree level and those from gluon-gluon fusion, which proceeds via quark and squark loops. We list compact results for the tree-level partonic cross sections and the squark loop amplitudes, and we confirm previous results for the quark loop amplitudes. We quantitatively analyze the hadronic cross sections at the CERN Large Hadron Collider assuming a favorable supergravity-inspired scenario.Comment: 22 pages (Latex), 16 figures (Postscript). Discussion of theoretical uncertainties and background processes added. Accepted for publication in Phys. Rev.

Toward One-Loop Tunneling Rates of Near-Extremal Magnetic Black Hole Pair-Production

Pair-production of magnetic Reissner-Nordstr\"{o}m black holes (of charges $\pm q$) was recently studied in the leading WKB approximation. Here, we consider generic quantum fluctuations in the corresponding instanton geometry given by the Euclidean Ernst metric, in order to simulate the behaviour of the one-loop tunneling rate. A detailed study of the Ernst metric suggests that for sufficiently weak field $B$, the problem can be reduced to that of quantum fluctuations around a single near-extremal Euclidean black hole in thermal equilibrium with a heat bath of finite size. After appropriate renormalization procedures, typical one-loop contributions to the WKB exponent are shown to be inversely proportional to $B$, as $B\rightarrow 0$, indicating that the leading Schwinger term is corrected by a small fraction $\sim \hbar /q^2$. We demonstrate that this correction to the Schwinger term is actually due to a semiclassical shift of the black hole mass-to-charge ratio that persists even in the extremal limit. Finally we discuss a few loose ends.Comment: LaTeX, 27pp, one uuencoded figure (A few sentences are rephrased to prevent a possible confusion; an extra paragraph Commenting on the strictly extremal case is added.

Negative differential resistance in nanotube devices

Carbon nanotube junctions are predicted to exhibit negative differential resistance, with very high peak-to-valley current ratios even at room temperature. We treat both nanotube p-n junctions and undoped metal-nanotube-metal junctions, calculating quantum transport through the self-consistent potential within a tight-binding approximation. The undoped junctions in particular may be suitable for device integration.Comment: 4 pages, 4 figures, to appear in Physical Review Letter

Black Hole Pair Creation and the Entropy Factor

It is shown that in the instanton approximation the rate of creation of black holes is always enhanced by a factor of the exponential of the black hole entropy relative to the rate of creation of compact matter distributions (stars). This result holds for any generally covariant theory of gravitational and matter fields that can be expressed in Hamiltonian form. It generalizes the result obtained previously for the pair creation of magnetically charged black holes by a magnetic field in Einstein--Maxwell theory. The particular example of pair creation of electrically charged black holes by an electric field in Einstein--Maxwell theory is discussed in detail.Comment: (12 pages, ReVTeX) Revised version of "Pair Creation of Electrically Charged Black Holes". New section shows that the BH pair creation rate is enhanced by a factor $\exp(BH entropy)$ for any Hamiltonian gravity + matter theor

On the Nonlocal Equations and Nonlocal Charges Associated with the Harry Dym Hierarchy

A large class of nonlocal equations and nonlocal charges for the Harry Dym hierarchy is exhibited. They are obtained from nonlocal Casimirs associated with its bi-Hamiltonian structure. The Lax representation for some of these equations is also given.Comment: to appear in Journal of Mathematical Physics, 17 pages, Late

Criteria for the experimental observation of multi-dimensional optical solitons in saturable media

Criteria for experimental observation of multi-dimensional optical solitons in media with saturable refractive nonlinearities are developed. The criteria are applied to actual material parameters (characterizing the cubic self-focusing and quintic self-defocusing nonlinearities, two-photon loss, and optical-damage threshold) for various glasses. This way, we identify operation windows for soliton formation in these glasses. It is found that two-photon absorption sets stringent limits on the windows. We conclude that, while a well-defined window of parameters exists for two-dimensional solitons (spatial or spatiotemporal), for their three-dimensional spatiotemporal counterparts such a window \emph{does not} exist, due to the nonlinear loss in glasses.Comment: 8 pages, to appear in Phys. Rev.