7,476 research outputs found
Five-Dimensional Unification of the Cosmological Constant and the Photon Mass
Using a non-Riemannian geometry that is adapted to the 4+1 decomposition of
space-time in Kaluza-Klein theory, the translational part of the connection
form is related to the electromagnetic vector potential and a Stueckelberg
scalar. The consideration of a five-dimensional gravitational action functional
that shares the symmetries of the chosen geometry leads to a unification of the
four-dimensional cosmological term and a mass term for the vector potential.Comment: 8 pages, LaTe
Choosing an Organizational Structure for Your Aquaculture Business
There are approximately 2.3 million farms in the United States, ranging in size from small part-time farms to very large operations. Regardless of size, all farms are a form of business and can be organized or structured in several ways. Individuals involved in the business of fish farming need to be aware of the various organizational structures available to them, including sole proprietorship, partnerships (general and limited) and corporations (regular and subchapter-S). . The specific circumstances of the fish farm business dictate which of these structures is most suitable. For example, large farms with numerous employees and a large investment requirement may find it advantageous to consider a more formalized structure, such as a corporation
Anomalous slow fidelity decay for symmetry breaking perturbations
Symmetries as well as other special conditions can cause anomalous slowing
down of fidelity decay. These situations will be characterized, and a family of
random matrix models to emulate them generically presented. An analytic
solution based on exponentiated linear response will be given. For one
representative case the exact solution is obtained from a supersymmetric
calculation. The results agree well with dynamical calculations for a kicked
top.Comment: 4 pages, 2 figure
Torsion Degrees of Freedom in the Regge Calculus as Dislocations on the Simplicial Lattice
Using the notion of a general conical defect, the Regge Calculus is
generalized by allowing for dislocations on the simplicial lattice in addition
to the usual disclinations. Since disclinations and dislocations correspond to
curvature and torsion singularities, respectively, the method we propose
provides a natural way of discretizing gravitational theories with torsion
degrees of freedom like the Einstein-Cartan theory. A discrete version of the
Einstein-Cartan action is given and field equations are derived, demanding
stationarity of the action with respect to the discrete variables of the
theory
Combinatorial identities for binary necklaces from exact ray-splitting trace formulae
Based on an exact trace formula for a one-dimensional ray-splitting system,
we derive novel combinatorial identities for cyclic binary sequences (P\'olya
necklaces).Comment: 15 page
Parametric correlations versus fidelity decay: the symmetry breaking case
We derive fidelity decay and parametric energy correlations for random matrix
ensembles where time--reversal invariance of the original Hamiltonian is broken
by the perturbation. Like in the case of a symmetry conserving perturbation a
simple relation between both quantities can be established.Comment: 8 pages, 8 figure
Supersymmetric Extensions of Calogero--Moser--Sutherland like Models: Construction and Some Solutions
We introduce a new class of models for interacting particles. Our
construction is based on Jacobians for the radial coordinates on certain
superspaces. The resulting models contain two parameters determining the
strengths of the interactions. This extends and generalizes the models of the
Calogero--Moser--Sutherland type for interacting particles in ordinary spaces.
The latter ones are included in our models as special cases. Using results
which we obtained previously for spherical functions in superspaces, we obtain
various properties and some explicit forms for the solutions. We present
physical interpretations. Our models involve two kinds of interacting
particles. One of the models can be viewed as describing interacting electrons
in a lower and upper band of a one--dimensional semiconductor. Another model is
quasi--two--dimensional. Two kinds of particles are confined to two different
spatial directions, the interaction contains dipole--dipole or tensor forces.Comment: 21 pages, 4 figure
On the minimization of Dirichlet eigenvalues of the Laplace operator
We study the variational problem \inf \{\lambda_k(\Omega): \Omega\
\textup{open in}\ \R^m,\ |\Omega| < \infty, \ \h(\partial \Omega) \le 1 \},
where is the 'th eigenvalue of the Dirichlet Laplacian
acting in , \h(\partial \Omega) is the - dimensional
Hausdorff measure of the boundary of , and is the Lebesgue
measure of . If , and , then there exists a convex
minimiser . If , and if is a minimiser,
then is also a
minimiser, and is connected. Upper bounds are
obtained for the number of components of . It is shown that if
, and then has at most components.
Furthermore is connected in the following cases : (i) (ii) and (iii) and (iv) and
. Finally, upper bounds on the number of components are obtained for
minimisers for other constraints such as the Lebesgue measure and the torsional
rigidity.Comment: 16 page
Gain without inversion in a biased superlattice
Intersubband transitions in a superlattice under homogeneous electric field
is studied within the tight-binding approximation. Since the levels are
equi-populated, the non-zero response appears beyond the Born approximation.
Calculations are performed in the resonant approximation with scattering
processes exactly taken into account. The absorption coefficient is equal zero
for the resonant excitation while a negative absorption (gain without
inversion) takes place below the resonance. A detectable gain in the THz
spectral region is obtained for the low-doped -based superlattice and
spectral dependencies are analyzed taking into account the interplay between
homogeneous and inhomogeneous mechanisms of broadening.Comment: 6 pages, 4 figure
Active Galactic Nuclei with Candidate Intermediate-Mass Black Holes
We present an initial sample of 19 intermediate-mass black hole candidates in
active galactic nuclei culled from the First Data Release of the Sloan Digital
Sky Survey. Using the linewidth-luminosity-mass scaling relation established
for broad-line active nuclei, we estimate black hole masses in the range of 8 x
10^4 - 10^6 solar masses, a regime in which only two objects are currently
known. The absolute magnitudes are faint for active galactic nuclei, ranging
from M_g of -15 to -18 mag, while the bolometric luminosities are all close to
the Eddington limit. The entire sample formally satisfies the linewidth
criterion for so-called narrow-line Seyfert 1 galaxies; however, they display a
wider range of FeII and [OIII] (5007) line strengths than is typically observed
in this class of objects. Although the available imaging data are of
insufficient quality to ascertain the detailed morphologies of the host
galaxies, it is likely that the majority of the hosts are relatively late-type
systems. The host galaxies have estimated g-band luminosities ~ 1 mag fainter
than M* for the general galaxy population at z of 0.1. Beyond simply extending
the known mass range of central black holes in galactic nuclei, these objects
provide unique observational constraints on the progenitors of supermassive
black holes. They are also expected to contribute significantly to the
integrated signal for future gravitational wave experiments.Comment: ApJ Accepted, 13 pages, 9 figures, uses emulateapj.cl
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