8,866 research outputs found
Nuclear giant quadrupole resonances in spherical even-even nuclei
The dynamic collective model has been extended to quadrupole giant resonances in spherical nuclei. The splitting of giant dipole and giant quadrupole resonances due to their coupling to surface vibrations has been calculated for Sn isotopes. Agreement with recent γ-absorption measurements of the Livermore group has been found
Exit polling and racial bloc voting: Combining individual-level and RC ecological data
Despite its shortcomings, cross-level or ecological inference remains a
necessary part of some areas of quantitative inference, including in United
States voting rights litigation. Ecological inference suffers from a lack of
identification that, most agree, is best addressed by incorporating
individual-level data into the model. In this paper we test the limits of such
an incorporation by attempting it in the context of drawing inferences about
racial voting patterns using a combination of an exit poll and precinct-level
ecological data; accurate information about racial voting patterns is needed to
assess triggers in voting rights laws that can determine the composition of
United States legislative bodies. Specifically, we extend and study a hybrid
model that addresses two-way tables of arbitrary dimension. We apply the hybrid
model to an exit poll we administered in the City of Boston in 2008. Using the
resulting data as well as simulation, we compare the performance of a pure
ecological estimator, pure survey estimators using various sampling schemes and
our hybrid. We conclude that the hybrid estimator offers substantial benefits
by enabling substantive inferences about voting patterns not practicably
available without its use.Comment: Published in at http://dx.doi.org/10.1214/10-AOAS353 the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Quasi-exact Treatment of the Relativistic Generalized Isotonic Oscillator
We investigate the pseudospin symmetry case of a spin-1/2 particle governed
by the generalized isotonic oscillator, by presenting quasi exact polynomial
solutions to Dirac equation with pseudospin symmetry vector and scalar
potentials. The resulting equation is found to be quasi-exactly solvable owing
to the existence of a hidden algebraic structure. A systematic and
closed form solution to the basic equation is obtained using the Bethe ansatz
method. Analytic expression for the energy is obtain and the wavefunction is
derived in terms of the roots to a set of Bethe ansatz equations
Collective correlations in the giant dipole continuum of 12C
A continuum shell-model calculation based on the collective correlation model has been made for the giant resonance of 12C using the eigenchannel reaction theory. The low-lying negative-parity states of 11C and 11B have been taken into account by corehole coupling. Partial, total, and integrated photoabsorption cross sections are calculated for the region of the giant dipole resonance
Search for GRB afterglows in the ROSAT all-sky survey
We report on the status of our search for X-ray afterglows of gamma-ray
bursts (GRBs) using the ROSAT all-sky survey data. The number of potential
X-ray afterglow candidates with respect to the expected number of beamed GRBs
allows to constrain the relative beaming angles of GRB emission and afterglow
emission at about 1-5 hrs after the GRB.Comment: 3 pages A&A style, 1 color ps-figure; To appear in A&A Suppl. Series,
Proc. of Rome 1998 GRB workshop, also available from
http://www.aip.de/~jcg/publis.htm
Lifetime of molecule-atom mixtures near a Feshbach resonance in 40K
We report a dramatic magnetic field dependence in the lifetime of trapped,
ultracold diatomic molecules created through an s-wave Feshbach resonance in
40K. The molecule lifetime increases from less than 1 ms away from the Feshbach
resonance to greater than 100 ms near resonance. We also have measured the
trapped atom lifetime as a function of magnetic field near the Feshbach
resonance; we find that the atom loss is more pronounced on the side of the
resonance containing the molecular bound state
Deformation Energy Minima at Finite Mass Asymmetry
A very general saddle point nuclear shape may be found as a solution of an
integro-differential equation without giving apriori any shape parametrization.
By introducing phenomenological shell corrections one obtains minima of
deformation energy for binary fission of parent nuclei at a finite (non-zero)
mass asymmetry. Results are presented for reflection asymmetric saddle point
shapes of thorium and uranium even-mass isotopes with A=226-238 and A=230-238
respectively.Comment: 5 pages, 2 Postscript figures, REVTeX, Version 4.
Unlike particle correlations and the strange quark matter distillation process
We present a new technique for observing the strange quark matter
distillation process based on unlike particle correlations. A simulation is
presented based on the scenario of a two-phase thermodynamical evolution model.Comment: 15 pages, 2 figures, 1 tabl
- …