163,758 research outputs found
Two-component theory of a droplet of electrons in half-filled Landau level
We have investigated low energy excitations of a disk of electrons in
half-filled Landau level using trail wave function and small-size exact
diagonalization approaches. We have constructed a set of many-body basis states
that describe correctly the low energy excitations. In this theory a droplet
consists of two types of composite fermion liquids, and suggests that a droplet
can support an edge magnetoplasmon and low energy droplet excitations. A
possibility of measuring these excitations in a quantum dot is discussed.Comment: Figure1 is available from the authors upon request. Three eps files
are attached to the tex fil
Government spending shocks and the multiplier: New evidence from the U.S. based on natural disasters
The literature on estimating macroeconomic effects of fiscal policy requires suitable instruments to identify exogenous and unanticipated spending shocks. So far, the instrument of choice has been military build-ups. This instrument, however, largely limits the analysis to the US as few other countries have been involved in mainly extraterritorial conflicts. Moreover, the expenditure associated with military build-ups affects primarily the defense sector so that the resulting multiplier does not necessarily approximate the effects of changes to general government spending. We propose an alternative instrument: government relief expenditure in the wake of natural disasters which is more similar in its scope to general government spending. We construct a rich data set of natural disasters and the corresponding government responses at the US state level. We apply this methodology both at the state as well as national levels and show that natural disasters serve as a powerful instrument for identifying government spending shocks. Furthermore, we show that the multiplier pertaining to non-defense government spending is higher than the defense-spending multiplier estimated in the literature using military build-ups
Angular momentum transport and element mixing in the stellar interior I. Application to the rotating Sun
The purpose of this work was to obtain diffusion coefficient for the magnetic
angular momentum transport and material transport in a rotating solar model. We
assumed that the transport of both angular momentum and chemical elements
caused by magnetic fields could be treated as a diffusion process. The
diffusion coefficient depends on the stellar radius, angular velocity, and the
configuration of magnetic fields. By using of this coefficient, it is found
that our model becomes more consistent with the helioseismic results of total
angular momentum, angular momentum density, and the rotation rate in a
radiative region than the one without magnetic fields. Not only can the
magnetic fields redistribute angular momentum efficiently, but they can also
strengthen the coupling between the radiative and convective zones. As a
result, the sharp gradient of the rotation rate is reduced at the bottom of the
convective zone. The thickness of the layer of sharp radial change in the
rotation rate is about 0.036 in our model. Furthermore, the
difference of the sound-speed square between the seismic Sun and the model is
improved by mixing the material that is associated with angular momentum
transport.Comment: 8 pages, 2 figure
Solar Models with Revised Abundances and Opacities
Using reconstructed opacities, we construct solar models with low
heavy-element abundance. Rotational mixing and enhanced diffusion of helium and
heavy elements are used to reconcile the recently observed abundances with
helioseismology. The sound speed and density of models where the relative and
absolute diffusion coefficients for helium and heavy elements have been
increased agree with seismically inferred values at better than the 0.005 and
0.02 fractional level respectively. However, the surface helium abundance of
the enhanced diffusion model is too low. The low helium problem in the enhanced
diffusion model can be solved to a great extent by rotational mixing. The
surface helium and the convection zone depth of rotating model M04R3, which has
a surface Z of 0.0154, agree with the seismic results at the levels of 1
and 3 respectively. M04R3 is almost as good as the standard
model M98. Some discrepancies between the models constructed in accord with the
new element abundances and seismic constraints can be solved individually, but
it seems difficult to resolve them as a whole scenario.Comment: 10 pages, 1 figur
Determinant representations of scalar products for the open XXZ chain with non-diagonal boundary terms
With the help of the F-basis provided by the Drinfeld twist or factorizing
F-matrix for the open XXZ spin chain with non-diagonal boundary terms, we
obtain the determinant representations of the scalar products of Bethe states
of the model.Comment: Latex file, 28 pages, based on the talk given by W. -L. Yang at
Statphys 24, Cairns, Australia, 19-23 July, 201
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Reaction Mechanisms for Long-Life Rechargeable Zn/MnO 2 Batteries
Rechargeable aqueous Zn-ion batteries (ZIBs) are very promising for large-scale grid energy storage applications owing to their low cost, environmentally benign constituents, excellent safety, and relatively high energy density. Their usage, however, is largely hampered by the fast capacity fade. The complexity of the reactions has resulted in long-standing ambiguities of the chemical pathways of Zn/MnO 2 system. In this study, we find that both H + /Zn 2+ intercalation and conversion reactions occur at different voltages and that the rapid capacity fading can clearly be ascribed to the rate-limiting and irreversible conversion reactions at a lower voltage. By limiting the irreversible conversion reactions at â1.26 V, we successfully demonstrate ultrahigh power and long life that are superior to most of the reported ZIBs or even some lithium-ion batteries
Differential Entropy on Statistical Spaces
We show that the previously introduced concept of distance on statistical
spaces leads to a straightforward definition of differential entropy on these
statistical spaces. These spaces are characterized by the fact that their
points can only be localized within a certain volume and exhibit thus a feature
of fuzziness. This implies that Riemann integrability of relevant integrals is
no longer secured. Some discussion on the specialization of this formalism to
quantum states concludes the paper.Comment: 4 pages, to appear in the proceedings of the joint meeting of the 2nd
International Conference on Cybernetics and Information Technologies, Systems
and Applications (CITSA 2005) and the 11th International Conference on
Information Systems Analysis and Synthesis (ISAS 2005), to be held in
Orlando, USA, on July 14-17, 200
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