3,162 research outputs found
The Theoretical and Experimental Determination of the Input Impedance of a Small Loop of Electric Current Immersed in an Anisotropic Plasma
Exact expression for input impedance of small loop of electric current when loop is immersed in infinite, homogeneous, cold anisotropic plasm
A classification of the dispersion surfaces in a magneto-ionic medium and a study of the associated radiation patterns scientific report no. 2
Dispersion surface classification in magnetoionic medium and associated radiation pattern
Charged Particles and the Electro-Magnetic Field in Non-Inertial Frames of Minkowski Spacetime: I. Admissible 3+1 Splittings of Minkowski Spacetime and the Non-Inertial Rest Frames
By using the 3+1 point of view and parametrized Minkowski theories we develop
the theory of {\it non-inertial} frames in Minkowski space-time. The transition
from a non-inertial frame to another one is a gauge transformation connecting
the respective notions of instantaneous 3-space (clock synchronization
convention) and of the 3-coordinates inside them. As a particular case we get
the extension of the inertial rest-frame instant form of dynamics to the
non-inertial rest-frame one. We show that every isolated system can be
described as an external decoupled non-covariant canonical center of mass
(described by frozen Jacobi data) carrying a pole-dipole structure: the
invariant mass and an effective spin. Moreover we identify the constraints
eliminating the internal 3-center of mass inside the instantaneous 3-spaces. In
the case of the isolated system of positive-energy scalar particles with
Grassmann-valued electric charges plus the electro-magnetic field we obtain
both Maxwell equations and their Hamiltonian description in non-inertial
frames. Then by means of a non-covariant decomposition we define the
non-inertial radiation gauge and we find the form of the non-covariant Coulomb
potential. We identify the coordinate-dependent relativistic inertial
potentials and we show that they have the correct Newtonian limit. In the
second paper we will study properties of Maxwell equations in non-inertial
frames like the wrap-up effect and the Faraday rotation in astrophysics. Also
the 3+1 description without coordinate-singularities of the rotating disk and
the Sagnac effect will be given, with added comments on pulsar magnetosphere
and on a relativistic extension of the Earth-fixed coordinate system.Comment: This paper and the second one are an adaptation of arXiv 0812.3057
for publication on Int.J.Geom. Methods in Modern Phys. 77
Putting String/Fivebrane Duality to the Test
According to string/fivebrane duality, the Green-Schwarz factorization of the
spacetime anomaly polynomial into means that just
as is the anomaly polynomial of the string worldsheet so
should be the anomaly polynomial of the fivebrane worldvolume. To test
this idea we perform a fivebrane calculation of and find perfect
agreement with the string one--loop result.Comment: 14 pages, CERN TH-6614/92, CTP-TAMU 60/9
Well-Posed Two-Temperature Constitutive Equations for Stable Dense Fluid Shockwaves using Molecular Dynamics and Generalizations of Navier-Stokes-Fourier Continuum Mechanics
Guided by molecular dynamics simulations, we generalize the
Navier-Stokes-Fourier constitutive equations and the continuum motion equations
to include both transverse and longitudinal temperatures. To do so we partition
the contributions of the heat transfer, the work done, and the heat flux vector
between the longitudinal and transverse temperatures. With shockwave boundary
conditions time-dependent solutions of these equations converge to give
stationary shockwave profiles. The profiles include anisotropic temperature and
can be fitted to molecular dynamics results, demonstrating the utility and
simplicity of a two-temperature description of far-from-equilibrium states.Comment: 19 pages with 10 figures, revised following review at Physical Review
E and with additional figure/discussion, for presentation at the
International Summer School and Conference "Advanced Problems in Mechanics"
[Saint Petersburg, Russia] 1-5 July 2010
Variational QMC study of a Hydrogen atom in jellium with comparison to LSDA and LSDA-SIC solutions
A Hydrogen atom immersed in a finite jellium sphere is solved using
variational quantum Monte Carlo (VQMC). The same system is also solved using
density functional theory (DFT), in both the local spin density (LSDA) and
self-interaction correction (SIC) approximations. The immersion energies
calculated using these methods, as functions of the background density of the
jellium, are found to lie within 1eV of each other with minima in approximately
the same positions. The DFT results show overbinding relative to the VQMC
result. The immersion energies also suggest an improved performance of the SIC
over the LSDA relative to the VQMC results. The atom-induced density is also
calculated and shows a difference between the methods, with a more extended
Friedel oscillation in the case of the VQMC result.Comment: 16 pages, 9 Postscript figure
Timelike Hopf Duality and Type IIA^* String Solutions
The usual T-duality that relates the type IIA and IIB theories compactified
on circles of inversely-related radii does not operate if the dimensional
reduction is performed on the time direction rather than a spatial one. This
observation led to the recent proposal that there might exist two further
ten-dimensional theories, namely type IIA^* and type IIB^*, related to type IIB
and type IIA respectively by a timelike dimensional reduction. In this paper we
explore such dimensional reductions in cases where time is the coordinate of a
non-trivial U(1) fibre bundle. We focus in particular on situations where there
is an odd-dimensional anti-de Sitter spacetime AdS_{2n+1}, which can be
described as a U(1) bundle over \widetilde{CP}^n, a non-compact version of CP^n
corresponding to the coset manifold SU(n,1)/U(n). In particular, we study the
AdS_5\times S^5 and AdS_7\times S^4 solutions of type IIB supergravity and
eleven-dimensional supergravity. Applying a timelike Hopf T-duality
transformation to the former provides a new solution of the type IIA^* theory,
of the form \widetilde{CP}^2\times S^1\times S^5. We show how the Hopf-reduced
solutions provide further examples of ``supersymmetry without supersymmetry.''
We also present a detailed discussion of the geometrical structure of the
Hopf-fibred metric on AdS_{2n+1}, and its relation to the horospherical metric
that arises in the AdS/CFT correspondence.Comment: Latex, 26 page
Intersecting branes and Supersymmetry
We consider intersecting M-brane solutions of supergravity in eleven
dimensions. Supersymmetry turns out to be a powerful tool in obtaining such
solutions and their generalizations.Comment: 6 pages, Latex, Presented at Supersymmetry and Quantum Field Theory,
International Seminar dedicated to the memory of D. V. Volkov, Kharkov, 199
Dimensional reduction of 4d heterotic string black holes
We perform the spherical symmetric dimensional reduction of
heterotic string theory. We find a class of two-dimensional (2d) dilaton
gravity models that gives a general description of the near-horizon,
near-extremal behavior of four-dimensional (4d) heterotic string black holes.
We show that the duality group of the 4d theory is realized in two dimensions
in terms of Weyl transformations of the metric. We use the 2d dilaton gravity
theory to compute the statistical entropy of the near-extremal 4d,
, black hole.Comment: 12 pages, LaTex fil
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