7,447 research outputs found
U.S. Election Assistance Commission Urban-Rural Study: Final Report
In May, the U.S. Election Assistance Commission released a report comparing election administration in urban and rural jurisdictions. The survey uncovered more similarities than differences, in part because many small, urban jurisdictions have more in common with rural offices than with very large metropolitan ones. The size of the registered voter population seemed to influence administration more than did the degree of urbanization.The report was based on a national survey of local election administrators that focused on voter-outreach efforts and office personnel -- topics identified by a working group of election officials and researchers as likely to vary based on a jurisdiction's urbanization
A conjectural generating function for numbers of curves on surfaces
I give a conjectural generating function for the numbers of -nodal
curves in a linear system of dimension on an algebraic surface. It
reproduces the results of Vainsencher for the case and
Kleiman-Piene for the case . The numbers of curves are expressed
in terms of five universal power series, three of which I give explicitly as
quasimodular forms. This gives in particular the numbers of curves of arbitrary
genus on a K3 surface and an abelian surface in terms of quasimodular forms,
generalizing the formula of Yau-Zaslow for rational curves on K3 surfaces. The
coefficients of the other two power series can be determined by comparing with
the recursive formulas of Caporaso-Harris for the Severi degrees in . We
verify the conjecture for genus 2 curves on an abelian surface. We also discuss
a link of this problem with Hilbert schemes of points.Comment: amslatex 13 page
X-ray and optical observations of three clusters of galaxies: Abell 901, Abell 1437, and Abell 3570
We analyse three clusters of galaxies, Abell 901 (z=0.17), Abell 1437
(z=0.13) and Abell 3570 (z=0.037). They have low to intermediate X-ray fluxes
and an irregular morphology in the ROSAT All-Sky Survey (RASS). These clusters
are chosen to test the abilities and limitations of the RASS in terms of
cluster fluxes and cluster morphologies. Therefore some ``worst'' cases are
used here. X-ray observations with the ROSAT/HRI and optical spectroscopic
observations are carried out. The ROSAT/HRI observations, which have a much
better spatial resolution than the RASS, reveal in two of the three cases a
significantly different morphology than seen in the RASS. The reasons are point
sources which could not be resolved in the RASS and were therefore confused
with the cluster emission. For A3570 we could confirm the relaxed state of the
cluster by the optical determination of a small velocity dispersion. In the
cluster with the lowest flux (Abell 901) the countrate measurement is strongly
affected by point sources, in the two other cases the countrate measurements of
the RASS are reliable, i.e. they are reproduced by the ROSAT/HRI measurement.
We conclude that for clusters with a flux of a few times 10^{-12} erg/cm^2/s or
smaller, which show at the same time a non-relaxed morphology, the flux
measurement of the RASS can be seriously affected by fore- or background
sources. We point out that an all-sky survey of a second ABRIXAS mission would
provide a much clearer source distinction for low-flux clusters and thus a much
improved countrate determination.Comment: 8 pages (incl. 6 figures), accepted for publication in A&A (Suppl.
On a filtered multiplicative basis of group algebras
Let be a field of characteristic and a nonabelian metacyclic
finite -group. We give an explicit list of all metacyclic -groups ,
such that the group algebra over a field of characteristic has a
filtered multiplicative -basis. We also present an example of a
non-metacyclic 2-group , such that the group algebra over any field of
characteristic 2 has a filtered multiplicative -basis.Comment: 10 pages, AMS-Te
Extension of the Brinkman-Rice picture and the Mott transition
In order to explain the metal-Mott-insulator transition, the Brinkman-Rice
(BR) picture is extended. In the case of less than one as well as one electron
per atom, the on-site Coulomb repulsion is given by U={kappa}{rho}^2U_c by
averaging the electron charge per atom over all atomic sites, where {kappa} is
the correlation strength of U, {rho} is the band filling factor, and U_c is the
critical on-site Coulomb energy. The effective mass of a quasiparticle is found
to be m*/m=1/{1-{kappa}^2{rho}^4} for 0<{kappa}{rho}^2<1 and seems to follow
the heat capacity data of Sr_{1-x}La_xTiO_3 and YBa_2Cu_3O_{7-delta} at
{kappa}=1 and 0<{kappa}{rho}^2<1. The Mott transition of the first order occurs
at {kappa}{rho}^2=1 and a band-type metal-insulator transition takes place at
{kappa}{rho}^2=0. This Mott transition is compared with that in the d=infinity
Hubbard model. The effective mass for 2D-DOS instead of the vHs can be used for
the mechanism of high T_c superconductivity.Comment: RevTex, Physica C, Vol. 341-348, 259-260 (2000
Neutrino Experiments : Highlights
This article consists of two parts. The first section presents the highlights
on the goals of neutrino physics, status of the current neutrino experiments
and future directions and program. The second section describes the theme,
program and research efforts for the TEXONO Collaboration among scientists from
Taiwan and China.Comment: 7 pages, 7 figure; Invited Contributions to the Proceedings of ``The
Fifth International Workshop on Particle Physics Phenomenology (PPP2000)'
Critical exponents at the superconductor-insulator transition in dirty-boson systems
I obtain the inverse of the correlation length exponent at the
superfluid-Bose glass quantum critical point as a series in small parameter
, with d being the dimensionality of the system, and compute the
first two terms using a novel field-theoretic technique. For d=2 I find and , for short-range and Coulomb interactions between
bosons, respectively. When combined with the exact values of the dynamical
critical exponents and , these results are in quantitative
agreement with the experiments on onset of superfluidity in in porous
glasses, and on superconductor-insulator transition in homogeneous metallic
films, in support of the dirty-boson theory fot the latter. Higher-order
calculation of the exponents and of the universal conductivity is discussed.Comment: 4 pages, RevTex, eq. 10 correcte
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