6,153 research outputs found
Quantization and simulation of Born-Infeld non-linear electrodynamics on a lattice
Born-Infeld non-linear electrodynamics arises naturally as a field theory
description of the dynamics of strings and branes. Most analyses of this theory
have been limited to studying it as a classical field theory. We quantize this
theory on a Euclidean 4-dimensional space-time lattice and determine its
properties using Monte-Carlo simulations. The electromagnetic field around a
static point charge is measured using Luscher-Weisz methods to overcome the
sign problem associated with the introduction of this charge. The D field
appears identical to that of Maxwell QED. However, the E field is enhanced by
quantum fluctuations, while still showing the short distance screening observed
in the classical theory. In addition, whereas for the classical theory, the
screening increases without bound as the non-linearity increases, the quantum
theory approaches a limiting conformal field theory.Comment: 24 pages, 10 figures. Latex with postscript figure
Gravitating monopoles and black holes in Einstein-Born-Infeld-Higgs model
We find static spherically symmetric monopoles in Einstein-Born-Infeld-Higgs
model in 3+1 dimensions. The solutions exist only when a parameter \a
(related to the strength of Gravitational interaction) does not exceed certain
critical value. We also discuss magnetically charged non Abelian black holes in
this model. We analyse these solutions numerically.Comment: LaTex,10 pages, 5figure
Nonperturbative calculation of Born-Infeld effects on the Schroedinger spectrum of the hydrogen atom
We present the first nonperturbative numerical calculations of the
nonrelativistic hydrogen spectrum as predicted by first-quantized
electrodynamics with nonlinear Maxwell-Born-Infeld field equations. We also
show rigorous upper and lower bounds on the ground state.
When judged against empirical data our results significantly restrict the
range of viable values of the new electromagnetic constant which is introduced
by the Born-Infeld theory.
We assess Born's own proposal for the value of his constant.Comment: 4p., 2 figs, 1 table; submitted for publicatio
Dynamics of the Born-Infeld dyons
The approach to the dynamics of a charged particle in the Born-Infeld
nonlinear electrodynamics developed in [Phys. Lett. A 240 (1998) 8] is
generalized to include a Born-Infeld dyon. Both Hamiltonian and Lagrangian
structures of many dyons interacting with nonlinear electromagnetism are
constructed. All results are manifestly duality invariant.Comment: 11 pages, LATE
Superconductivity in Boron under pressure - why are the measured T's so low?
Using the full potential linear muffin-tin orbitals (FP-LMTO) method we
examine the pressure-dependence of superconductivity in the two metallic phases
of Boron: bct and fcc. Linear response calculations are carried out to examine
the phonon frequencies and electron-phonon coupling for various lattice
parameters, and superconducting transition temperatures are obtained from the
Eliashberg equation. In both bct and fcc phases the superconducting transition
temperature T is found to decrease with increasing pressure, due to
stiffening of phonons with an accompanying decrease in electron-phonon
coupling. This is in contrast to a recent report, where T is found to
increase with pressure. Even more drastic is the difference between the
measured T, in the range 4-11 K, and the calculated values for both bct and
fcc phases, in the range 60-100 K. The calculation reveals that the transition
from the fcc to bct phase, as a result of increasing volume or decreasing
pressure, is caused by the softening of the X-point transverse phonons. This
phonon softening also causes large electron-phonon coupling for high volumes in
the fcc phase, resulting in coupling constants in excess of 2.5 and T
nearing 100 K. We discuss possible causes as to why the experiment might have
revealed T's much lower than what is suggested by the present study. The
main assertion of this paper is that the possibility of high T, in excess
of 50 K, in high pressure pure metallic phases of boron cannot be ruled out,
thus substantiating the need for further experimental investigations of the
superconducting properties of high pressure pure phases of boron.Comment: 16 pages, 8 figures, 1 Tabl
In search of a working notion of lex sportiva
The emergence of a lex specialis regime and its interaction with the established, governing lex generalis in their overlapping spheres of application is always an intriguing legal relationship to explore. In this article, the focus will be on the development of legal principles and rules that have been/can be collectively described as lex sportiva. However, it is notable that those involved in the consideration, usage and application of this notion have not agreed as to the scope and delimitation of the concept. It is debated whether lex sportiva exists in the first place, its legal sources and its purpose. The risk is for the concept becoming redundant when not vilified as a hidden strategy to exclude non-sports-related law from the ambit of sport. Through an examination of the different propositions to the framework of the term, this article will shed light on the existence, utility and limits of the development of this conceptualisation
A Monopole Solution in open String Theory
We investigate a solution of the Weyl invariance conditions in open string
theory in 4 dimensions. In the closed string sector this solution is a
combination of the SU(2) Wess--Zumino--Witten model and a Liouville theory. The
investigation is carried out in the model approach where we have
coupled all massless modes (especially an abelian gauge field via the boundary)
and tachyon fields. Neglecting all higher derivatives in the field strength we
get an exact result which can be interpreted as a monopole configuration living
in non--trivial space time. The masses of both tachyon fields are quantized by
and vanish for .Comment: 14 pages, Latex, DESY 93-15
Lateral shift of the transmitted light beam through a left-handed slab
It is reported that when a light beam travels through a slab of left-handed
medium in the air, the lateral shift of the transmitted beam can be negative as
well as positive. The necessary condition for the lateral shift to be positive
is given. The validity of the stationary-phase approach is demonstrated by
numerical simulations for a Gaussian-shaped beam. A restriction to the slab's
thickness is provided that is necessary for the beam to retain its profile in
the traveling. It is shown that the lateral shift of the reflected beam is
equal to that of the transmitted beam in the symmetric configuration.Comment: 14 pages, 4 figure
Evaluation of Born and local effective charges in unoriented materials from vibrational spectra
We present an application of the Lorentz model in which fits to vibrational
spectra or a Kramers Kronig analysis are employed along with several useful
formalisms to quantify microscopic charge in unoriented (powdered) materials.
The conditions under which these techniques can be employed are discussed, and
we analyze the vibrational response of a layered transition metal
dichalcogenide and its nanoscale analog to illustrate the utility of this
approach.Comment: 9 pages, 1 figur
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