3,886 research outputs found
Quantum Monte Carlo Calculations of Pion Scattering from Li
We show that the neutron and proton transition densities predicted by recent
quantum Monte Carlo calculations for A=6,7 nuclei are consistent with pion
scattering from 6Li and 7Li at energies near the Delta resonance. This has
provided a microscopic understanding of the enhancement factors for quadrople
excitations, which were needed to describe pion inelastic scattering within the
nuclear shell model of Cohen and Kurath.Comment: 10 pages, REVTeX, 3 postscript figures; added calculation of elastic
and inelastic pion scattering from 6Li at multiple energie
The Cross of Micronesia
The Cross of Micronesia. In the summer of 1970 the Congress of Mircronesia rejected a U.S, offer of commonwealth status; that would have enabled Micronesians to obtain U.S. citizenship easily and permitted an indefinite continuation of funds for the economically poor Trust Territory of the Pacific Islands
Lead-Free Piezoelectric Transducers for Microelectronic Wirebonding Applications
Author name used in this publication: K. W. KwokAuthor name used in this publication: S. H. ChoyAuthor name used in this publication: H. L. W. Chan2010-2011 > Academic research: refereed > Chapter in an edited book (author)published_fina
Proton-proton bremsstrahlung below and above pion-threshold: the influence of the -isobar
The proton-proton bremsstrahlung is investigated within a coupled-channel
model with the degree of freedom. The model is consistent with the
scattering up to 1 GeV and the vertex determined in the
study of pion photoproduction reactions. It is found that the
excitation can significantly improve the agreements with the at MeV. Predictions at and MeV are
presented for future experimental tests.Comment: 26 pages Revtex, 12 figures are available from the authors upon
request ([email protected]
Theory of Ferromagnetism in Diluted Magnetic Semiconductor Quantum Wells
We present a mean field theory of ferromagnetism in diluted magnetic
semiconductor quantum wells. When subband mixing due to exchange interactions
between quantum well free carriers and magnetic impurities is neglected,
analytic result can be obtained for the dependence of the critical temperature
and the spontaneous magnetization on the distribution of magnetic impurities
and the quantum well width. The validity of this approximate theory has been
tested by comparing its predictions with those from numerical self-consistent
field calculations. Interactions among free carriers, accounted for using the
local-spin-density approximation, substantially enhance the critical
temperature. We demonstrate that an external bias potential can tune the
critical temperature through a wide range.Comment: 4 pages, 3 figures, submitted to Phys. Rev.
On the controllability of bimodal piecewise linear systems
This paper studies controllability of bimodal systems that consist of two linear dynamics on each side of a given hyperplane. We show that the controllability properties of these systems can be inferred from those of linear systems for which the inputs are constrained in a certain way. Inspired by the earlier work on constrained controllability of linear systems, we derive necessary and sufficient conditions for a bimodal piecewise linear system to be controllable.Natl Sci Fdn; Univ Penn, Sch Engn & Appl Sci
Another tetraquark structure in the invariant mass distribution
In this article, we assume that there exists a scalar hidden charm tetraquark
state in the invariant mass distribution, and study its mass
using the QCD sum rules. The numerical result is
consistent with the mass of the Z(4250). The Z(4250) may be a tetraquark state,
other possibilities, such as a hadro-charmonium resonance and a
molecular state are not excluded.Comment: 14 pages, 14 figure, correct some type error
Low-Frequency Optical Conductivity in Inhomogeneous d-wave Superconductors
Motivated by the recent optical conductivity experiments on
Bi_2Sr_2CaCu_2O_{8+delta} films, we examine the possible origin of
low-frequency dissipation in the superconducting state. In the presence of
spatial inhomogeneity of the local phase stiffness rho_s, it is shown that some
spectral weight is removed from omega=0 to finite frequencies and contribute to
dissipation. A case where both rho_s and the local normal fluid density are
inhomogeneous is also considered. We find an enhanced dissipation at low
frequency if the two variations are anti-correlated.Comment: To appear in Phys. Rev.
Charge ordering and chemical potential shift in LaSrNiO studied by photoemission spectroscopy
We have studied the chemical potential shift in LaSrNiO and
the charge ordering transition in LaSrNiO by
photoemission spectroscopy. The result shows a large ( 1 eV/hole)
downward shift of the chemical potential with hole doping in the high-doping
regime ( 0.33) while the shift is suppressed in the low-doping
regime ( 0.33). This suppression is attributed to a
segregation of doped holes on a microscopic scale when the hole concentration
is lower than . In the sample, the
photoemission intensity at the chemical potential vanishes below the charge
ordering transition temperature 240 K.Comment: 5 pages, 4 figure
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