817 research outputs found
Migration and the Employment and Wages of Native and Immigrant Workers
This paper assesses the association between migration (both international and internal) and the employment status and earnings of young noncollege-educated native white, black, Hispanic, Asian, and immigrant white-collar and blue-collar workers in the United States during the decade from 1980 to 1990. We seek to determine (1) whether internal and/or international migration contributed to the increased joblessness observed for blacks, Asians, and Hispanics in the 1980s, particularly among males, and (2) whether migration contributed to the decline in the hourly wages of both native and immigrant workers in the 1980s. We present results which only partly support the claim that internal migrants and immigrants are substitutes for native workers. On the one hand, we find that migration (flow) was not a major factor associated with the increased joblessness and decreased wages experienced by some native groups during the 1980s, particularly among blue-collar workers. On the other hand, we do find that changes in the foreign-born composition of an industrial sector (a measure of immigrant stock) were associated with increased joblessness of native workers and decreased joblessness of immigrant workers.
Coherent Bayesian inference on compact binary inspirals using a network of interferometric gravitational wave detectors
Presented in this paper is a Markov chain Monte Carlo (MCMC) routine for
conducting coherent parameter estimation for interferometric gravitational wave
observations of an inspiral of binary compact objects using data from multiple
detectors. The MCMC technique uses data from several interferometers and infers
all nine of the parameters (ignoring spin) associated with the binary system,
including the distance to the source, the masses, and the location on the sky.
The Metropolis-algorithm utilises advanced MCMC techniques, such as importance
resampling and parallel tempering. The data is compared with time-domain
inspiral templates that are 2.5 post-Newtonian (PN) in phase and 2.0 PN in
amplitude. Our routine could be implemented as part of an inspiral detection
pipeline for a world wide network of detectors. Examples are given for
simulated signals and data as seen by the LIGO and Virgo detectors operating at
their design sensitivity.Comment: 10 pages, 4 figure
Supersymmetric Jaynes-Cummings model and its exact solutions
The super-algebraic structure of a generalized version of the Jaynes-Cummings
model is investigated. We find that a Z2 graded extension of the so(2,1) Lie
algebra is the underlying symmetry of this model. It is isomorphic to the
four-dimensional super-algebra u(1/1) with two odd and two even elements.
Differential matrix operators are taken as realization of the elements of the
superalgebra to which the model Hamiltonian belongs. Several examples with
various choices of superpotentials are presented. The energy spectrum and
corresponding wavefunctions are obtained analytically.Comment: 12 pages, no figure
Detailed balance has a counterpart in non-equilibrium steady states
When modelling driven steady states of matter, it is common practice either
to choose transition rates arbitrarily, or to assume that the principle of
detailed balance remains valid away from equilibrium. Neither of those
practices is theoretically well founded. Hypothesising ergodicity constrains
the transition rates in driven steady states to respect relations analogous to,
but different from the equilibrium principle of detailed balance. The
constraints arise from demanding that the design of any model system contains
no information extraneous to the microscopic laws of motion and the macroscopic
observables. This prevents over-description of the non-equilibrium reservoir,
and implies that not all stochastic equations of motion are equally valid. The
resulting recipe for transition rates has many features in common with
equilibrium statistical mechanics.Comment: Replaced with minor revisions to introduction and conclusions.
Accepted for publication in Journal of Physics
Supersymmetric and Shape-Invariant Generalization for Nonresonant and Intensity-Dependent Jaynes-Cummings Systems
A class of shape-invariant bound-state problems which represent transition in
a two-level system introduced earlier are generalized to include arbitrary
energy splittings between the two levels as well as intensity-dependent
interactions. We show that the couple-channel Hamiltonians obtained correspond
to the generalizations of the nonresonant and intensity-dependent nonresonant
Jaynes-Cummings Hamiltonians, widely used in quantized theories of laser. In
this general context, we determine the eigenstates, eigenvalues, the time
evolution matrix and the population inversion matrix factor.Comment: A combined version of quant-ph/0005045 and quant-ph/0005046. 24
pages, LATE
Controlled spontaneous emission
The problem of spontaneous emission is studied by a direct computer
simulation of the dynamics of a combined system: atom + radiation field. The
parameters of the discrete finite model, including up to 20k field oscillators,
have been optimized by a comparison with the exact solution for the case when
the oscillators have equidistant frequencies and equal coupling constants.
Simulation of the effect of multi-pulse sequence of phase kicks and emission by
a pair of atoms shows that both the frequency and the linewidth of the emitted
spectrum could be controlled.Comment: 25 pages including 11 figure
Entropic Dynamics, Time and Quantum Theory
Quantum mechanics is derived as an application of the method of maximum
entropy. No appeal is made to any underlying classical action principle whether
deterministic or stochastic. Instead, the basic assumption is that in addition
to the particles of interest x there exist extra variables y whose entropy S(x)
depends on x. The Schr\"odinger equation follows from their coupled dynamics:
the entropy S(x) drives the dynamics of the particles x while they in their
turn determine the evolution of S(x). In this "entropic dynamics" time is
introduced as a device to keep track of change. A welcome feature of such an
entropic time is that it naturally incorporates an arrow of time. Both the
magnitude and the phase of the wave function are given statistical
interpretations: the magnitude gives the distribution of x in agreement with
the usual Born rule and the phase carries information about the entropy S(x) of
the extra variables. Extending the model to include external electromagnetic
fields yields further insight into the nature of the quantum phase.Comment: 29 page
Tunneling in a cavity
The mechanism of coherent destruction of tunneling found by Grossmann et al.
[Phys. Rev. Lett. 67, 516 (1991)] is studied from the viewpoint of quantum
optics by considering the photon statistics of a single mode cavity field which
is strongly coupled to a two-level tunneling system (TS). As a function of the
interaction time between TS and cavity the photon statistics displays the
tunneling dynamics. In the semi-classical limit of high photon occupation
number , coherent destruction of tunneling is exhibited in a slowing down of
an amplitude modulation for certain parameter ratios of the field. The
phenomenon is explained as arising from interference between displaced number
states in phase space which survives the large limit due to identical
scaling between orbit width and displacement.Comment: 4 pages Revtex, 2 PS-figures, appears in The Physical Review
The Dirac Oscillator. A relativistic version of the Jaynes--Cummings model
The dynamics of wave packets in a relativistic Dirac oscillator is compared
to that of the Jaynes-Cummings model. The strong spin-orbit coupling of the
Dirac oscillator produces the entanglement of the spin with the orbital motion
similar to what is observed in the model of quantum optics. The collapses and
revivals of the spin which result extend to a relativistic theory our previous
findings on nonrelativistic oscillator where they were known under the name of
`spin-orbit pendulum'. There are important relativistic effects (lack of
periodicity, zitterbewegung, negative energy states). Many of them disappear
after a Foldy-Wouthuysen transformation.Comment: LaTeX2e, uses IOP style files (included), 14 pages, 9 separate
postscript figure
Consistent Application of Maximum Entropy to Quantum-Monte-Carlo Data
Bayesian statistics in the frame of the maximum entropy concept has widely
been used for inferential problems, particularly, to infer dynamic properties
of strongly correlated fermion systems from Quantum-Monte-Carlo (QMC) imaginary
time data. In current applications, however, a consistent treatment of the
error-covariance of the QMC data is missing. Here we present a closed Bayesian
approach to account consistently for the QMC-data.Comment: 13 pages, RevTeX, 2 uuencoded PostScript figure
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