1,769,679 research outputs found
On the kinematic signature of a central Galactic bar in observed star samples
A quasi self-consistent model for a barred structure in the central regions
of our Galaxy is used to calculate the signature of such a triaxial structure
on the kinematical properties of star samples. We argue that, due to the
presence of a velocity dispersion, such effects are much harder to detect in
the stellar component than in the gas. It might be almost impossible to detect
stellar kinematical evidence for a bar using only l-v diagrams, if there is no
a priori knowledge of the potential. Therefore, we propose some test parameters
that can easily be applied to observed star samples, and that also incorporate
distances or proper motions. We discus the diagnostic power of these tests as a
function of the sample size and the bar strength. We conclude that about 1000
stars would be necessary to diagnose triaxiality with some statistical
confidence.Comment: 9 pages + 8 PS figures, uses aas2pp4.sty. Accepted by Ap
Magneto-x-ray effects in transition-metal alloys
We present a theory that combines the relativistic spin-polarized version of the Koringa-Kohn-Rostoker coherent-potential approximation theory and the macroscopic theory of magneto-optical effects enabling us to calculate magneto-x-ray effects from first principles. The theory is illustrated by calculation of Faraday and Kerr rotations and ellipticities for transition-metal alloys
Superdeformed Bands of Odd Nuclei in A=190 Region in the Quasiparticle Picture
We study the properties of the superdeformed (SD) bands of 195Pb and 193Hg by
the cranked Hartree-Fock-Bogoliubov method. Our calculations reproduce the flat
behavior of the dynamical moment of inertia of two of the SD bands of 195Pb
measured recently. We discuss possible configuration assignments for the
observed bands 3 and 4 of 195Pb. We also calculate the two interacting SD bands
of 193Hg. Our analysis confirms the superiority of a density-dependent pairing
force over a seniority pairing interaction.Comment: 12 pages, 5 Postscript figures, submitted to Phys.Rev.
Tridiagonal realization of the anti-symmetric Gaussian -ensemble
The Householder reduction of a member of the anti-symmetric Gaussian unitary
ensemble gives an anti-symmetric tridiagonal matrix with all independent
elements. The random variables permit the introduction of a positive parameter
, and the eigenvalue probability density function of the corresponding
random matrices can be computed explicitly, as can the distribution of
, the first components of the eigenvectors. Three proofs are given.
One involves an inductive construction based on bordering of a family of random
matrices which are shown to have the same distributions as the anti-symmetric
tridiagonal matrices. This proof uses the Dixon-Anderson integral from Selberg
integral theory. A second proof involves the explicit computation of the
Jacobian for the change of variables between real anti-symmetric tridiagonal
matrices, its eigenvalues and . The third proof maps matrices from the
anti-symmetric Gaussian -ensemble to those realizing particular examples
of the Laguerre -ensemble. In addition to these proofs, we note some
simple properties of the shooting eigenvector and associated Pr\"ufer phases of
the random matrices.Comment: 22 pages; replaced with a new version containing orthogonal
transformation proof for both cases (Method III
On Killing vectors in initial value problems for asymptotically flat space-times
The existence of symmetries in asymptotically flat space-times are studied
from the point of view of initial value problems. General necessary and
sufficient (implicit) conditions are given for the existence of Killing vector
fields in the asymptotic characteristic and in the hyperboloidal initial value
problem (both of them are formulated on the conformally compactified space-time
manifold)
Local twistors and the conformal field equations
This note establishes the connection between Friedrich's conformal field
equations and the conformally invariant formalism of local twistors.Comment: LaTeX2e Minor corrections of misprints et
Transverse Entanglement Migration in Hilbert Space
We show that, although the amount of mutual entanglement of photons
propagating in free space is fixed, the type of correlations between the
photons that determine the entanglement can dramatically change during
propagation. We show that this amounts to a migration of entanglement in
Hilbert space, rather than real space. For the case of spontaneous parametric
down conversion, the migration of entanglement in transverse coordinates takes
place from modulus to phase of the bi-photon state and back again. We propose
an experiment to observe this migration in Hilbert space and to determine the
full entanglement.Comment: 4 pages, 3 figure
General solution of an exact correlation function factorization in conformal field theory
We discuss a correlation function factorization, which relates a three-point
function to the square root of three two-point functions. This factorization is
known to hold for certain scaling operators at the two-dimensional percolation
point and in a few other cases. The correlation functions are evaluated in the
upper half-plane (or any conformally equivalent region) with operators at two
arbitrary points on the real axis, and a third arbitrary point on either the
real axis or in the interior. This type of result is of interest because it is
both exact and universal, relates higher-order correlation functions to
lower-order ones, and has a simple interpretation in terms of cluster or loop
probabilities in several statistical models. This motivated us to use the
techniques of conformal field theory to determine the general conditions for
its validity.
Here, we discover a correlation function which factorizes in this way for any
central charge c, generalizing previous results. In particular, the
factorization holds for either FK (Fortuin-Kasteleyn) or spin clusters in the
Q-state Potts models; it also applies to either the dense or dilute phases of
the O(n) loop models. Further, only one other non-trivial set of highest-weight
operators (in an irreducible Verma module) factorizes in this way. In this case
the operators have negative dimension (for c < 1) and do not seem to have a
physical realization.Comment: 7 pages, 1 figure, v2 minor revision
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