1,762 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.
Electron-magnon coupling and nonlinear tunneling transport in magnetic nanoparticles
We present a theory of single-electron tunneling transport through a
ferromagnetic nanoparticle in which particle-hole excitations are coupled to
spin collective modes. The model employed to describe the interaction between
quasiparticles and collective excitations captures the salient features of a
recent microscopic study. Our analysis of nonlinear quantum transport in the
regime of weak coupling to the external electrodes is based on a rate-equation
formalism for the nonequilibrium occupation probability of the nanoparticle
many-body states. For strong electron-boson coupling, we find that the
tunneling conductance as a function of bias voltage is characterized by a large
and dense set of resonances. Their magnetic field dependence in the large-field
regime is linear, with slopes of the same sign. Both features are in agreement
with recent tunneling experiments.Comment: 4 pages, 2 figure
Statistical mechanics in the context of special relativity
In the present effort we show that is the unique existing entropy obtained
by a continuous deformation of the Shannon-Boltzmann entropy and preserving unaltered its fundamental properties of concavity,
additivity and extensivity. Subsequently, we explain the origin of the
deformation mechanism introduced by and show that this deformation
emerges naturally within the Einstein special relativity. Furthermore, we
extend the theory in order to treat statistical systems in a time dependent and
relativistic context. Then, we show that it is possible to determine in a self
consistent scheme within the special relativity the values of the free
parameter which results to depend on the light speed and reduces
to zero as recovering in this way the ordinary statistical
mechanics and thermodynamics. The novel statistical mechanics constructed
starting from the above entropy, preserves unaltered the mathematical and
epistemological structure of the ordinary statistical mechanics and is suitable
to describe a very large class of experimentally observed phenomena in low and
high energy physics and in natural, economic and social sciences. Finally, in
order to test the correctness and predictability of the theory, as working
example we consider the cosmic rays spectrum, which spans 13 decades in energy
and 33 decades in flux, finding a high quality agreement between our
predictions and observed data.
PACS number(s): 05.20.-y, 51.10.+y, 03.30.+p, 02.20.-aComment: 17 pages (two columns), 5 figures, RevTeX4, minor typing correction
Strong-driving-assisted multipartite entanglement in cavity QED
We propose a method of generating multipartite entanglement by considering
the interaction of a system of N two-level atoms in a cavity of high quality
factor with a strong classical driving field. It is shown that, with a
judicious choice of the cavity detuning and the applied coherent field
detuning, vacuum Rabi coupling produces a large number of important
multipartite entangled states. It is even possible to produce entangled states
involving different cavity modes. Tuning of parameters also permits us to
switch from Jaynes-Cummings to anti-Jaynes-Cummings like interaction.Comment: Last version with minor changes and added references. Accepted for
publication in Phys. Rev. Letter
Illusory Decoherence
If a quantum experiment includes random processes, then the results of
repeated measurements can appear consistent with irreversible decoherence even
if the system's evolution prior to measurement was reversible and unitary. Two
thought experiments are constructed as examples.Comment: 10 pages, 3 figure
Reconstruction of motional states of neutral atoms via MaxEnt principle
We present a scheme for a reconstruction of states of quantum systems from
incomplete tomographic-like data. The proposed scheme is based on the Jaynes
principle of Maximum Entropy. We apply our algorithm for a reconstruction of
motional quantum states of neutral atoms. As an example we analyze the
experimental data obtained by the group of C. Salomon at the ENS in Paris and
we reconstruct Wigner functions of motional quantum states of Cs atoms trapped
in an optical lattice
Information Theory based on Non-additive Information Content
We generalize the Shannon's information theory in a nonadditive way by
focusing on the source coding theorem. The nonadditive information content we
adopted is consistent with the concept of the form invariance structure of the
nonextensive entropy. Some general properties of the nonadditive information
entropy are studied, in addition, the relation between the nonadditivity
and the codeword length is pointed out.Comment: 9 pages, no figures, RevTex, accepted for publication in Phys. Rev.
E(an error in proof of theorem 1 was corrected, typos corrected
Bayesian Updating Rules in Continuous Opinion Dynamics Models
In this article, I investigate the use of Bayesian updating rules applied to
modeling social agents in the case of continuos opinions models. Given another
agent statement about the continuous value of a variable , we will see that
interesting dynamics emerge when an agent assigns a likelihood to that value
that is a mixture of a Gaussian and a Uniform distribution. This represents the
idea the other agent might have no idea about what he is talking about. The
effect of updating only the first moments of the distribution will be studied.
and we will see that this generates results similar to those of the Bounded
Confidence models. By also updating the second moment, several different
opinions always survive in the long run. However, depending on the probability
of error and initial uncertainty, those opinions might be clustered around a
central value.Comment: 14 pages, 5 figures, presented at SigmaPhi200
James van Allen and his namesake NASA mission
Abstract
In many ways, James A. Van Allen defined and “invented” modern space research. His example showed the way for government-university partners to pursue basic research that also served important national and international goals. He was a tireless advocate for space exploration and for the role of space science in the spectrum of national priorities
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
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