7,274 research outputs found
Availability of Credit and Loan Default: A Look at the Commercial Mortgage Supply Cycle
This study uses a structural equation approach to assess the presence of a credit supply effect in the commercial mortgage market and the lenders' ability to incorporate expectations about this effect into their lending policies. A credit supply effect is defined as the effect of mortgage supply on the level of loan defaults. The empirical analysis shows two important results. First, changes in loan defaults appear to be followed by changes in commercial mortgage supply with a lag of approximately four to five years. Second, lenders tend to behave myopically, failing to incorporate expectations about the credit supply effect into their lending policies. Additionally, a simulation suggests that adequate timing of the mortgage supply cycle is crucial in limiting the incidence of mortgage default.
Inter-Center Retail Externalities
This paper empirically examines inter-center externalities in regional shopping centers. Specifically, we use a non-linear retail share model to measure the impact that department store size and image in subject and competitive centers have on subject center in-line retail sales. Our findings reveal that department store size and image attributes have a significant and non-linear impact on subject center sales. More importantly, the results show that the effect of department store fashion image dominates that of department store size
Stability of toroidal magnetic fields in stellar interiors
We present 3D MHD simulations of purely toroidal and mixed poloidal-toroidal
magnetic field configurations to study the behavior of the Tayler instability.
For the first time the simultaneous action of rotation and magnetic diffusion
are taken into account and the effects of a poloidal field on the dynamic
evolution of unstable toroidal magnetic fields is included. In the absence of
diffusion, fast rotation (rotation rate compared to Alfv\'en frequency) is able
to suppress the instability when the rotation and magnetic axes are aligned and
when the radial field strength gradient p < 1.5. When diffusion is included,
this system turns unstable for diffusion dominated and marginally diffusive
dominated regions. If the magnetic and rotation axes are perpendicular to each
other the stabilizing effect induced by the Coriolis force is scale dependent
and decreases with increasing wavenumber. In toroidal fields with radial field
gradients bigger than p > 1.5, rapid rotation does not suppress the instability
but instead introduces a damping factor to the growth rate in agreement with
the analytic predictions. For the mixed poloidal-toroidal fields we find an
unstable axisymmetric mode, not predicted analytically, right at the stability
threshold for the non-axisymmetric modes; it has been argued that an
axisymmetric mode is necessary for the closure of the Tayler-Spruit dynamo
loop.Comment: 12 pages, 12 figures. Accepted for publication in A&
Transport properties of a modified Lorentz gas
We present a detailed study of the first simple mechanical system that shows
fully realistic transport behavior while still being exactly solvable at the
level of equilibrium statistical mechanics. The system under consideration is a
Lorentz gas with fixed freely-rotating circular scatterers interacting with
point particles via perfectly rough collisions. Upon imposing a temperature
and/or a chemical potential gradient, a stationary state is attained for which
local thermal equilibrium holds for low values of the imposed gradients.
Transport in this system is normal, in the sense that the transport
coefficients which characterize the flow of heat and matter are finite in the
thermodynamic limit. Moreover, the two flows are non-trivially coupled,
satisfying Onsager's reciprocity relations to within numerical accuracy as well
as the Green-Kubo relations . We further show numerically that an applied
electric field causes the same currents as the corresponding chemical potential
gradient in first order of the applied field. Puzzling discrepancies in higher
order effects (Joule heating) are also observed. Finally, the role of entropy
production in this purely Hamiltonian system is shortly discussed.Comment: 16 pages, 16 figures, submitted to J. Stat. Phy
First passages for a search by a swarm of independent random searchers
In this paper we study some aspects of search for an immobile target by a
swarm of N non-communicating, randomly moving searchers (numbered by the index
k, k = 1, 2,..., N), which all start their random motion simultaneously at the
same point in space. For each realization of the search process, we record the
unordered set of time moments \{\tau_k\}, where \tau_k is the time of the first
passage of the k-th searcher to the location of the target. Clearly, \tau_k's
are independent, identically distributed random variables with the same
distribution function \Psi(\tau). We evaluate then the distribution P(\omega)
of the random variable \omega \sim \tau_1/bar{\tau}, where bar{\tau} = N^{-1}
\sum_{k=1}^N \tau_k is the ensemble-averaged realization-dependent first
passage time. We show that P(\omega) exhibits quite a non-trivial and sometimes
a counterintuitive behaviour. We demonstrate that in some well-studied cases
e.g., Brownian motion in finite d-dimensional domains) the \textit{mean} first
passage time is not a robust measure of the search efficiency, despite the fact
that \Psi(\tau) has moments of arbitrary order. This implies, in particular,
that even in this simplest case (not saying about complex systems and/or
anomalous diffusion) first passage data extracted from a single particle
tracking should be regarded with an appropriate caution because of the
significant sample-to-sample fluctuations.Comment: 35 pages, 18 figures, to appear in JSTA
Quantum and classical echoes in scattering systems described by simple Smale horseshoes
We explore the quantum scattering of systems classically described by binary
and other low order Smale horseshoes, in a stage of development where the
stable island associated with the inner periodic orbit is large, but chaos
around this island is well developed. For short incoming pulses we find
periodic echoes modulating an exponential decay over many periods. The period
is directly related to the development stage of the horseshoe. We exemplify our
studies with a one-dimensional system periodically kicked in time and we
mention possible experiments.Comment: 7 pages with 6 reduced quality figures! Please contact the authors
([email protected]) for an original good quality pre-prin
Nonequlibrium particle and energy currents in quantum chains connected to mesoscopic Fermi reservoirs
We propose a model of nonequilibrium quantum transport of particles and
energy in a system connected to mesoscopic Fermi reservoirs (meso-reservoir).
The meso-reservoirs are in turn thermalized to prescribed temperatures and
chemical potentials by a simple dissipative mechanism described by the Lindblad
equation. As an example, we study transport in monoatomic and diatomic chains
of non-interacting spinless fermions. We show numerically the breakdown of the
Onsager reciprocity relation due to the dissipative terms of the model.Comment: 5pages, 4 figure
Spectroscopic Interpretation: The High Vibrations of CDBrClF
We extract the dynamics implicit in an algebraic fitted model Hamiltonian for
the deuterium chromophore's vibrational motion in the molecule CDBrClF. The
original model has 4 degrees of freedom, three positions and one representing
interbond couplings. A conserved polyad allows in a semiclassical approach the
reduction to 3 degrees of freedom. For most quantum states we can identify the
underlying motion that when quantized gives the said state. Most of the
classifications, identifications and assignments are done by visual inspection
of the already available wave function semiclassically transformed from the
number representation to a representation on the reduced dimension toroidal
configuration space corresponding to the classical action and angle variables.
The concentration of the wave function density to lower dimensional subsets
centered on idealized simple lower dimensional organizing structures and the
behavior of the phase along such organizing centers already reveals the atomic
motion. Extremely little computational work is needed.Comment: 23 pages, 6 figures. Accepted for publication in J. Chem. Phy
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