50,409 research outputs found
Sit-and-Wait Strategies in Dynamic Visual Search
The role of memory in visual search has lately become a controversial issue. Horowitz and Wolfe (1998) observed that performance in a visual search task was little affected by whether the stimuli were static or randomly relocated every 111 ms. Because a memory-based mechanism, such as inhibition of return, would be of no use in the dynamic condition, Horowitz and Wolfe concluded that memory is likewise not involved in the static condition. However, Horowitz and Wolfe could not effectively rule out the possibility that observers adopted a different strategy in the dynamic condition than in the static condition. That is, in the dynamic condition observers may have attended to a subregion of the display and waited for the target to appear there (sit-and-wait strategy). This hypothesis is supported by experimental data showing that performance in their dynamic condition does not differ from performance in another dynamic condition in which observers are forced to adopt a sit-and-wait strategy by being presented with a limited region of the display only
Multi-messenger observations of neutron rich matter
Neutron rich matter is central to many fundamental questions in nuclear
physics and astrophysics. Moreover, this material is being studied with an
extraordinary variety of new tools such as the Facility for Rare Isotope Beams
(FRIB) and the Laser Interferometer Gravitational Wave Observatory (LIGO). We
describe the Lead Radius Experiment (PREX) that uses parity violating electron
scattering to measure the neutron radius in Pb. This has important
implications for neutron stars and their crusts. We discuss X-ray observations
of neutron star radii. These also have important implications for neutron rich
matter. Gravitational waves (GW) open a new window on neutron rich matter. They
come from sources such as neutron star mergers, rotating neutron star
mountains, and collective r-mode oscillations. Using large scale molecular
dynamics simulations, we find neutron star crust to be very strong. It can
support mountains on rotating neutron stars large enough to generate detectable
gravitational waves. Finally, neutrinos from core collapse supernovae (SN)
provide another, qualitatively different probe of neutron rich matter.
Neutrinos escape from the surface of last scattering known as the
neutrino-sphere. This is a low density warm gas of neutron rich matter.
Observations of neutrinos can probe nucleosyntheses in SN. Simulations of SN
depend on the equation of state (EOS) of neutron rich matter. We discuss a new
EOS based on virial and relativistic mean field calculations. We believe that
combing astronomical observations using photos, GW, and neutrinos, with
laboratory experiments on nuclei, heavy ion collisions, and radioactive beams
will fundamentally advance our knowledge of compact objects in the heavens, the
dense phases of QCD, the origin of the elements, and of neutron rich matter.Comment: 13 pages, 4 figures, Added discussion of dipole polarizability, pygmy
resonances, and neutron skin
Direct Labor Market Effects of Unemployment Insurance
[Excerpt] With high current interest in unemployment and inflation, policy makers and academicians have begun to reassess the impact of unemployment insurance on the labor market. Some ask whether high unemployment rates are partly the result of an addition to the labor market of workers with a high propensity for unemployment. Others see unemployment as being partly caused by an increasing tendency for workers to refuse “bad” jobs. Still others concentrate on the factors that lead to greater labor turnover and flows of workers through the labor market. Consequently, there has evolved a “new view” of unemployment, which considers more than the familiar concepts of deficient demand and structural and seasonal unemployment. It also pays attention to job search processes and the instability of certain jobs and certain workers.
Based on this “new view,” this paper seeks to gauge the impact of the American system of unemployment insurance (UI) on the labor market. The evaluative issues are: the efficiency of UI as a tool for income maintenance, the extent to which UI leads to greater unemployment, and UI’s income distribution effects
Asymptotic quasinormal modes of a coupled scalar field in the Gibbons-Maeda dilaton spacetime
Adopting the monodromy technique devised by Motl and Neitzke, we investigate
analytically the asymptotic quasinormal frequencies of a coupled scalar field
in the Gibbons-Maeda dilaton spacetime. We find that it is described by , which depends on the structure
parameters of the background spacetime and on the coupling between the scalar
and gravitational fields. As the parameters and tend to zero,
the real parts of the asymptotic quasinormal frequencies becomes ,
which is consistent with Hod's conjecture. When , the formula
becomes that of the Reissner-Nordstr\"{o}m spacetime.Comment: 6 pages, 1 figur
Neutron rich matter, neutron stars, and their crusts
Neutron rich matter is at the heart of many fundamental questions in Nuclear
Physics and Astrophysics. What are the high density phases of QCD? Where did
the chemical elements come from? What is the structure of many compact and
energetic objects in the heavens, and what determines their electromagnetic,
neutrino, and gravitational-wave radiations? Moreover, neutron rich matter is
being studied with an extraordinary variety of new tools such as Facility for
Rare Isotope Beams (FRIB) and the Laser Interferometer Gravitational Wave
Observatory (LIGO). We describe the Lead Radius Experiment (PREX) that is using
parity violation to measure the neutron radius in 208Pb. This has important
implications for neutron stars and their crusts. Using large scale molecular
dynamics, we model the formation of solids in both white dwarfs and neutron
stars. We find neutron star crust to be the strongest material known, some 10
billion times stronger than steel. It can support mountains on rotating neutron
stars large enough to generate detectable gravitational waves. Finally, we
describe a new equation of state for supernova and neutron star merger
simulations based on the Virial expansion at low densities, and large scale
relativistic mean field calculations.Comment: 10 pages, 2 figures, Plenary talk International Nuclear Physics
Conference 2010, Vancouver, C
A smoothed maximum score estimator for the binary choice panel data model with individual fixed effects and applications to labour force participation
In a binary choice panel data model with individual effects and two time periods, Manski proposed the maximum score estimator, based on a discontinuous objective function, and proved its consistency under weak distributional assumptions. However, the rate of convergence of this estimator is low (N) and its limit distribution cannot be used for making inference. This paper overcomes this problem by applying the idea of Horowitz to smooth Manski's objective function. The paper extends the resulting smoothed maximum score estimator to the case of more than two time periods and to unbalanced panels (assuming away selectivity effects). Under weak assumptions the estimator is consistent and asymptotically normal with a rate of convergence that is at least N 2/5 and can be made arbitrarily close to N1/2, depending on the strength of the smoothness assumptions imposed. Statistical inferences can be made. The estimator is applied to an equation for labour force participation of married Dutch.Estimation;Labour Supply;Panel Data;Labour Participation;smoothing;statistics
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