3,765 research outputs found
Extreme objects with arbitrary large mass, or density, and arbitrary size
We consider a generalization of the interior Schwarzschild solution that we
match to the exterior one to build global C^1 models that can have arbitrary
large mass, or density, with arbitrary size. This is possible because of a new
insight into the problem of localizing the center of symmetry of the models and
the use of principal transformations to understand the structure of space.Comment: 20 pages, 6 figures. Fixed one reference. Added a new equatio
Relativistic Corrections in a Three-Boson System of Equal Masses
Three-body systems of scalar bosons are described in the framework of
relativistic constraint dynamics. With help of a change of variables followed
by a change of wave function, two redundant degrees of freedom get eliminated
and the mass-shell constraints can be reduced to a three-dimensional eigenvalue
problem.
In general, this problem is complicated, but for three equal masses a drastic
simplification arises at the first post-Galilean order: the reduced wave
equation becomes tractable, and we can compute a first-order correction beyond
the nonrelativistic limit. The harmonic interaction is displayed as a toy
model.Comment: 16 pages, no figure. Several points clarified, one typo corrected.
References added. To appear in Physical Review
Single molecule photon counting statistics for quantum mechanical chromophore dynamics
We extend the generating function technique for calculation of single
molecule photon emission statistics [Y. Zheng and F. L. H. Brown, Phys. Rev.
Lett., 90,238305 (2003)] to systems governed by multi-level quantum dynamics.
This opens up the possibility to study phenomena that are outside the realm of
purely stochastic and mixed quantum-stochastic models. In particular, the
present methodology allows for calculation of photon statistics that are
spectrally resolved and subject to quantum coherence. Several model
calculations illustrate the generality of the technique and highlight
quantitative and qualitative differences between quantum mechanical models and
related stochastic approximations. Calculations suggest that studying photon
statistics as a function of photon frequency has the potential to reveal more
about system dynamics than the usual broadband detection schemes.Comment: Submitted to the Journal of Physical Chemistr
Frame dragging and super-energy
We show that the vorticity appearing in stationary vacuum spacetimes is
always related to the existence of a flow of super-energy on the plane
orthogonal to the vorticity vector. This result, toghether with the previously
established link between vorticity and super--energy in radiative (Bondi-Sachs)
spacetimes strength further the case for this latter quantity as the cause of
frame dragging.Comment: 12 pages Latex. To appear in Phys.Rev. D. Typos correcte
Ambipolar Nernst effect in NbSe
The first study of Nernst effect in NbSe reveals a large quasi-particle
contribution with a magnitude comparable and a sign opposite to the vortex
signal. Comparing the effect of the Charge Density Wave(CDW) transition on Hall
and Nernst coefficients, we argue that this large Nernst signal originates from
the thermally-induced counterflow of electrons and holes and indicates a
drastic change in the electron scattering rate in the CDW state. The results
provide new input for the debate on the origin of the anomalous Nernst signal
in high-T cuprates.Comment: 5 pages including 4 figure
Comparing metrics at large: harmonic vs quo-harmonic coordinates
To compare two space-times on large domains, and in particular the global
structure of their manifolds, requires using identical frames of reference and
associated coordinate conditions. In this paper we use and compare two classes
of time-like congruences and corresponding adapted coordinates: the harmonic
and quo-harmonic classes. Besides the intrinsic definition and some of their
intrinsic properties and differences we consider with some detail their
differences at the level of the linearized approximation of the field
equations. The hard part of this paper is an explicit and general determination
of the harmonic and quo-harmonic coordinates adapted to the stationary
character of three well-know metrics, Schwarzschild's, Curzon's and Kerr's, to
order five of their asymptotic expansions. It also contains some relevant
remarks on such problems as defining the multipoles of vacuum solutions or
matching interior and exterior solutions.Comment: 27 pages, no figure
Degeneracy measures for the algebraic classification of numerical spacetimes
We study the issue of algebraic classification of the Weyl curvature tensor,
with a particular focus on numerical relativity simulations. The spacetimes of
interest in this context, binary black hole mergers, and the ringdowns that
follow them, present subtleties in that they are generically, strictly
speaking, Type I, but in many regions approximately, in some sense, Type D. To
provide meaning to any claims of "approximate" Petrov class, one must define a
measure of degeneracy on the space of null rays at a point. We will investigate
such a measure, used recently to argue that certain binary black hole merger
simulations ring down to the Kerr geometry, after hanging up for some time in
Petrov Type II. In particular, we argue that this hangup in Petrov Type II is
an artefact of the particular measure being used, and that a geometrically
better-motivated measure shows a black hole merger produced by our group
settling directly to Petrov Type D.Comment: 14 pages, 7 figures. Version 2 adds two references
A Random Walk to a Non-Ergodic Equilibrium Concept
Random walk models, such as the trap model, continuous time random walks, and
comb models exhibit weak ergodicity breaking, when the average waiting time is
infinite. The open question is: what statistical mechanical theory replaces the
canonical Boltzmann-Gibbs theory for such systems? In this manuscript a
non-ergodic equilibrium concept is investigated, for a continuous time random
walk model in a potential field. In particular we show that in the non-ergodic
phase the distribution of the occupation time of the particle on a given
lattice point, approaches U or W shaped distributions related to the arcsin
law. We show that when conditions of detailed balance are applied, these
distributions depend on the partition function of the problem, thus
establishing a relation between the non-ergodic dynamics and canonical
statistical mechanics. In the ergodic phase the distribution function of the
occupation times approaches a delta function centered on the value predicted
based on standard Boltzmann-Gibbs statistics. Relation of our work with single
molecule experiments is briefly discussed.Comment: 14 pages, 6 figure
The Dynamical Behaviour of Test Particles in a Quasi-Spherical Spacetime and the Physical Meaning of Superenergy
We calculate the instantaneous proper radial acceleration of test particles
(as measured by a locally defined Lorentzian observer) in a Weyl spacetime,
close to the horizon. As expected from the Israel theorem, there appear some
bifurcations with respect to the spherically symmetric case (Schwarzschild),
which are explained in terms of the behaviour of the superenergy, bringing out
the physical relevance of this quantity in the study of general relativistic
systems.Comment: 14 pages, Latex. 4 figures. New references added. Typos corrected. To
appear in Int. J. Theor. Phy
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