1,166,283 research outputs found
Selection Wages and Discrimination
Applicants for any given job are more or less suited to fill it, and the firm will select the best among them. Increasing the wage offer attracts more applicants and makes it possible to raise the hiring standard and improve the productivity of the staff. Wages that optimize on the trade-off between the wage level and the productivity of the workforce are known as selection wages. As men react more strongly to wage differentials than females, the trade-off is more pronounced for men and a profit-maximizing firm will offer a higher wage for men than for women in equilibrium
Flexibly Instructable Agents
This paper presents an approach to learning from situated, interactive
tutorial instruction within an ongoing agent. Tutorial instruction is a
flexible (and thus powerful) paradigm for teaching tasks because it allows an
instructor to communicate whatever types of knowledge an agent might need in
whatever situations might arise. To support this flexibility, however, the
agent must be able to learn multiple kinds of knowledge from a broad range of
instructional interactions. Our approach, called situated explanation, achieves
such learning through a combination of analytic and inductive techniques. It
combines a form of explanation-based learning that is situated for each
instruction with a full suite of contextually guided responses to incomplete
explanations. The approach is implemented in an agent called Instructo-Soar
that learns hierarchies of new tasks and other domain knowledge from
interactive natural language instructions. Instructo-Soar meets three key
requirements of flexible instructability that distinguish it from previous
systems: (1) it can take known or unknown commands at any instruction point;
(2) it can handle instructions that apply to either its current situation or to
a hypothetical situation specified in language (as in, for instance,
conditional instructions); and (3) it can learn, from instructions, each class
of knowledge it uses to perform tasks.Comment: See http://www.jair.org/ for any accompanying file
Sub-Milliarcsecond Precision of Pulsar Motions: Using In-Beam Calibrators with the VLBA
We present Very Long Baseline Array phase-referenced measurements of the
parallax and proper motion of two pulsars, B0919+06 and B1857-26.
Sub-milliarcsecond positional accuracy was obtained by simultaneously observing
a weak calibrator source within the 40' field of view of the VLBA at 1.5 GHz.
We discuss the merits of using weak close calibrator sources for VLBI
observations at low frequencies, and outline a method of observation and data
reduction for these type of measurements. For the pulsar B1919+06 we measure a
parallax of 0.31 +/- 0.14 mas. The accuracy of the proper motions is
approximately 0.5 mas, an order of magnitude improvement over most previous
determinations.Comment: 11 pages plus 4 figures. In press, Astronomical Journa
Distant Entanglement of Macroscopic Gas Samples
One of the main ingredients in most quantum information protocols is a
reliable source of two entangled systems. Such systems have been generated
experimentally several years ago for light but has only in the past few years
been demonstrated for atomic systems. None of these approaches however involve
two atomic systems situated in separate environments. This is necessary for the
creation of entanglement over arbitrary distances which is required for many
quantum information protocols such as atomic teleportation. We present an
experimental realization of such distant entanglement based on an adaptation of
the entanglement of macroscopic gas samples containing about 10^11 cesium atoms
shown previously by our group. The entanglement is generated via the
off-resonant Kerr interaction between the atomic samples and a pulse of light.
The achieved entanglement distance is 0.35m but can be scaled arbitrarily. The
feasibility of an implementation of various quantum information protocols using
macroscopic samples of atoms has therefore been greatly increased. We also
present a theoretical modeling in terms of canonical position and momentum
operators X and P describing the entanglement generation and verification in
presence of decoherence mechanisms.Comment: 20 pages book-style, 3 figure
Coupled Cluster Treatment of the XY model
We study quantum spin systems in the 1D, 2D square and 3D cubic lattices with
nearest-neighbour XY exchange. We use the coupled-cluster method (CCM) to
calculate the ground-state energy, the T=0 sublattice magnetisation and the
excited state energies, all as functions of the anisotropy parameter .
We consider in detail and give some results for higher . In 1D these
results are compared with the exact results and in 2D with Monte-Carlo
and series expansions. We obtain critical points close to the expected value
and our extrapolated LSUBn results for the ground-state energy are
well converged for all except very close to the critical point.Comment: 11 pages, Latex, 4 postscript figure, accepted by J.Phys.: Condens.
Matte
Two-colour QCD at non-zero quark-number density
We have simulated two-colour four-flavour QCD at non-zero chemical potential
for quark number. Simulations were performed on and lattices. Clear evidence was seen for the formation of a colourless diquark
condensate which breaks quark number spontaneously, for . The transition appears to be second order. We have measured the
spectrum of scalar and pseudoscalar bosons which shows clear evidence for the
expected Goldstone boson. Our results are in qualitative agreement with those
from effective Lagrangians for the potential Goldstone excitations of this
theory.Comment: 22 pages RevTeX, 6 figures in 10 postscript file
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