Wightman Functions' Behaviour on the Event Horizon of an Extremal Reissner-Nordstr\"om Black Hole

A weaker Haag, Narnhofer and Stein prescription as well as a weaker Hessling Quantum Equivalence Principle for the behaviour of thermal Wightman functions on an event horizon are analysed in the case of an extremal Reissner-Nordstr\"{o}m black hole in the limit of a large mass. In order to avoid the degeneracy of the metric in the stationary coordinates on the horizon, a method is introduced which employs the invariant length of geodesics which pass the horizon. First the method is checked for a massless scalar field on the event horizon of the Rindler wedge, extending the original procedure of Haag, Narnhofer and Stein onto the {\em whole horizon} and recovering the same results found by Hessling. Afterwards the HNS prescription and Hessling's prescription for a massless scalar field are analysed on the whole horizon of an extremal Reissner-Nordstr\"{o}m black hole in the limit of a large mass. It is proved that the weak form of the HNS prescription is satisfyed for all the finite values of the temperature of the KMS states, i.e., this principle does not determine any Hawking temperature. It is found that the Reissner-Nordstr\"{o}m vacuum, i.e., $T=0$ does satisfy the weak HNS prescription and it is the only state which satisfies weak Hessling's prescription, too. Finally, it is suggested that all the previously obtained results should be valid dropping the requirements of a massless field and of a large mass black hole.Comment: 27 pages, standard LaTex, no figures, final version containing the results following from Hessling's principle as they appeared in the other paper gr-qc/9510016, minor changes in the text and in references, it will appear on Class. Quant. Gra

There are No Causality Problems for Fermi's Two Atom System

A repeatedly discussed gedanken experiment, proposed by Fermi to check Einstein causality, is reconsidered. It is shown that, contrary to a recent statement made by Hegerfeldt, there appears no causality paradoxon in a proper theoretical description of the experiment.Comment: 6 pages, latex, DESY 94-02

Nickel hydrogen low Earth orbit test program update and status

The current status of nickel-hydrogen (NiH2) testing ongong at NWSC, Crane In, and The Aerospace Corporation, El Segundo, Ca are described. The objective of this testing is to develop a database for NiH2 battery use in Low Earth Orbit (LEO) and support applications in Medium Altitude Orbit (MAO). Individual pressure vessel-type cells are being tested. A minimum of 200 cells (3.5 in diameter and 4.5 in diameter) are included in the test, from four U.S. vendors. As of this date (Nov. 18, 1986) approximately 60 cells have completed preliminary testing (acceptance, characterization, and environmental testing) and have gone into life cycling

The Quest for Understanding in Relativistic Quantum Physics

We discuss the status and some perspectives of relativistic quantum physics.Comment: Invited contribution to the Special Issue 2000 of the Journal of Mathematical Physics, 38 pages, typos corrected and references added, as to appear in JM

Canonical Quantization Inside the Schwarzschild Black Hole

We propose a scheme for quantizing a scalar field over the Schwarzschild manifold including the interior of the horizon. On the exterior, the timelike Killing vector and on the horizon the isometry corresponding to restricted Lorentz boosts can be used to enforce the spectral condition. For the interior we appeal to the need for CPT invariance to construct an explicitly positive definite operator which allows identification of positive and negative frequencies. This operator is the translation operator corresponding to the inexorable propagation to smaller radii as expected from the classical metric. We also propose an expression for the propagator in the interior and express it as a mode sum.Comment: 8 pages, LaTex. Title altered. One reference added. A few typos esp. eq.(7),(38) corrected. To appear in Class.Q.Gra

Decoherence of Macroscopic Closed Systems within Newtonian Quantum Gravity

A theory recently proposed by the author aims to explain decoherence and the thermodynamical behaviour of closed systems within a conservative, unitary, framework for quantum gravity by assuming that the operators tied to the gravitational degrees of freedom are unobservable and equating physical entropy with matter-gravity entanglement entropy. Here we obtain preliminary results on the extent of decoherence this theory predicts. We treat first a static state which, if one were to ignore quantum gravitational effects, would be a quantum superposition of two spatially displaced states of a single classically well describable ball of uniform mass density in empty space. Estimating the quantum gravitational effects on this system within a simple Newtonian approximation, we obtain formulae which predict e.g. that as long as the mass of the ball is considerably larger than the Planck mass, such a would-be-coherent static superposition will actually be decohered whenever the separation of the centres of mass of the two ball-states excedes a small fraction (which decreases as the mass of the ball increases) of the ball radius. We then obtain a formula for the quantum gravitational correction to the would-be-pure density matrix of a non-relativistic many-body Schroedinger wave function and argue that this formula predicts decoherence between configurations which differ (at least) in the "relocation" of a cluster of particles of Planck mass. We estimate the entropy of some simple model closed systems, finding a tendency for it to increase with "matter-clumping" suggestive of a link with existing phenomenological discussions of cosmological entropy increase.Comment: 11 pages, plain TeX, no figures. Accepted for publication as a "Letter to the Editor" in "Classical and Quantum Gravity

Test Facility and Preliminary Performance of a 100 kW Class MPD Thruster

A 260 kW magnetoplasmadynamic (MPD) thruster test facility was assembled and used to characterize thrusters at power levels up to 130 kW using argon and helium propellants. Sensitivities of discharge characteristics to arc current, mass flow rate, and applied magnetic field were investigated. A thermal efficiency correlation developed by others for low power MPD thrusters defined parametric guidelines to minimize electrode losses in MPD thrusters. Argon and helium results suggest that a parameter defined as the product of arc voltage and the square root of the mass flow rate must exceed 0.7 V/kg(sup 1/2)/sec(sup 1/2) in order to obtain thermal efficiencies in excess of 60 percent

Medium power hydrogen arcjet performance

An experimental investigation was performed to evaluate hydrogen arcjet operating characteristics in the range of 1 to 4 kW. A series of nozzles were operated in modular laboratory thrusters to examine the effects of geometric parameters such as constrictor diameter and nozzle divergence angle. Each nozzle was tested over a range of current and mass flow rates to explore stability and performance. In the range of mass flow rates and power levels tested, specific impulse values between 650 and 1250 sec were obtained at efficiencies between 30 and 40 percent. The performance of the two larger half angle (20, 15 deg) nozzles was similar for each of the two constrictor diameters tested. The nozzles with the smallest half angle (10 deg) were difiicult to operate. A restrike mode of operation was identified and described. Damage in the form of melting was observed in the constrictor region of all the nozzle inserts tested. Arcjet ignition was also difficult in many tests and a glow discharge mode that prevents starting was identified

Superfield Realizations of Lorentz and CPT Violation

Superfield realizations of Lorentz-violating extensions of the Wess-Zumino model are presented. These models retain supersymmetry but include terms that explicitly break the Lorentz symmetry. The models can be understood as arising from superspace transformations that are modifications of the familiar one in the Lorentz-symmetric case.Comment: 10 page

CFT fusion rules, DHR gauge groups, and CAR algebras

It is demonstrated that several series of conformal field theories, while satisfying braid group statistics, can still be described in the conventional setting of the DHR theory, i.e. their superselection structure can be understood in terms of a compact DHR gauge group. Besides theories with only simple sectors, these include (the untwisted part of) c=1 orbifold theories and level two so(N) WZW theories. We also analyze the relation between these models and theories of complex free fermions.Comment: 22 pages, LaTeX2