46,049 research outputs found
Recent developments in perturbation theory
Rayleigh-Schroeder perturbation theory - degenerate and non-degenerate states - quantum chemistry - other perturbation equation
Comprehensive Spectral Analysis of Human EEG GENERATORS in Posterior Cerebral Regions
Human electroencephalogram generator spectral analysis in posterior cerebral region
The postulates of gravitational thermodynamics
The general principles and logical structure of a thermodynamic formalism
that incorporates strongly self-gravitating systems are presented. This
framework generalizes and simplifies the formulation of thermodynamics
developed by Callen. The definition of extensive variables, the homogeneity
properties of intensive parameters, and the fundamental problem of
gravitational thermodynamics are discussed in detail. In particular, extensive
parameters include quasilocal quantities and are naturally incorporated into a
set of basic general postulates for thermodynamics. These include additivity of
entropies (Massieu functions) and the generalized second law. Fundamental
equations are no longer homogeneous first-order functions of their extensive
variables. It is shown that the postulates lead to a formal resolution of the
fundamental problem despite non-additivity of extensive parameters and
thermodynamic potentials. Therefore, all the results of (gravitational)
thermodynamics are an outgrowth of these postulates. The origin and nature of
the differences with ordinary thermodynamics are analyzed. Consequences of the
formalism include the (spatially) inhomogeneous character of thermodynamic
equilibrium states, a reformulation of the Euler equation, and the absence of a
Gibbs-Duhem relation.Comment: 28 pages, Revtex, no figures. An important sentence and several minor
corrections included. To appear in Physical Review
Action Principle for the Generalized Harmonic Formulation of General Relativity
An action principle for the generalized harmonic formulation of general
relativity is presented. The action is a functional of the spacetime metric and
the gauge source vector. An action principle for the Z4 formulation of general
relativity has been proposed recently by Bona, Bona--Casas and Palenzuela
(BBP). The relationship between the generalized harmonic action and the BBP
action is discussed in detail.Comment: This version is contains more thorough presentations and discussions
of the key results. To be published in PRD. (8 pages, no figures
Microwave Power Transmission System Studies. Volume 1: Executive Summary
A study of microwave power generation, transmission, reception and control was conducted as a part of a program to demonstrate the feasibility of power transmission from geosynchronous orbit. A summary is presented of results concerning design approaches, estimated costs (ROM), critical technology, associated ground and orbital test programs with emphasis on dc to rf conversion, transmitting antenna, phase control, mechanical systems, flight operations, ground power receiving-rectifying antenna with systems analysis, and evaluation. Recommendations for early further in-depth studies complementing the technology program are included
Microwave power transmission system studies. Volume 2: Introduction, organization, environmental and spaceborne systems analyses
Introduction, organization, analyses, conclusions, and recommendations for each of the spaceborne subsystems are presented. Environmental effects - propagation analyses are presented with appendices covering radio wave diffraction by random ionospheric irregularities, self-focusing plasma instabilities and ohmic heating of the D-region. Analyses of dc to rf conversion subsystems and system considerations for both the amplitron and the klystron are included with appendices for the klystron covering cavity circuit calculations, output power of the solenoid-focused klystron, thermal control system, and confined flow focusing of a relativistic beam. The photovoltaic power source characteristics are discussed as they apply to interfacing with the power distribution flow paths, magnetic field interaction, dc to rf converter protection, power distribution including estimates for the power budget, weights, and costs. Analyses for the transmitting antenna consider the aperture illumination and size, with associated efficiencies and ground power distributions. Analyses of subarray types and dimensions, attitude error, flatness, phase error, subarray layout, frequency tolerance, attenuation, waveguide dimensional tolerances, mechanical including thermal considerations are included. Implications associated with transportation, assembly and packaging, attitude control and alignment are discussed. The phase front control subsystem, including both ground based pilot signal driven adaptive and ground command approaches with their associated phase errors, are analyzed
Thermodynamics of Reissner-Nordstrom-anti-de Sitter black holes in the grand canonical ensemble
The thermodynamical properties of the Reissner-Nordstr\"om-anti-de Sitter
black hole in the grand canonical ensemble are investigated using York's
formalism. The black hole is enclosed in a cavity with finite radius where the
temperature and electrostatic potential are fixed. The boundary conditions
allow us to compute the relevant thermodynamical quantities, e.g. thermal
energy, entropy and charge. The stability conditions imply that there are
thermodynamically stable black hole solutions, under certain conditions.
Instantons with negative heat capacity are also found.Comment: 15 pages, 9 figures, Revtex. Published version. Changes: figures
added to tex
Hamiltonian thermodynamics of the Reissner-Nordstr\"om-anti-de Sitter black hole
We consider the Hamiltonian dynamics and thermodynamics of spherically
symmetric Einstein-Maxwell spacetimes with a negative cosmological constant. We
impose boundary conditions that enforce every classical solution to be an
exterior region of a Reissner-Nordstr\"om-anti-de Sitter black hole with a
nondegenerate Killing horizon, with the spacelike hypersurfaces extending from
the horizon bifurcation two-sphere to the asymptotically anti-de Sitter
infinity. The constraints are simplified by a canonical transformation, which
generalizes that given by Kucha\v{r} in the spherically symmetric vacuum
Einstein theory, and the theory is reduced to its true dynamical degrees of
freedom. After quantization, the grand partition function of a thermodynamical
grand canonical ensemble is obtained by analytically continuing the Lorentzian
time evolution operator to imaginary time and taking the trace. A~similar
analysis under slightly modified boundary conditions leads to the partition
function of a thermodynamical canonical ensemble. The thermodynamics in each
ensemble is analyzed, and the conditions that the (grand) partition function be
dominated by a classical Euclidean black hole solution are found. When these
conditions are satisfied, we recover in particular the Bekenstein-Hawking
entropy. The limit of a vanishing cosmological constant is briefly discussed.
(This paper is dedicated to Karel Kucha\v{r} on the occasion of his sixtieth
birthday.)Comment: 34 pages, REVTeX v3.0. (Minor corrections and presentational
revisions; added references.
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