2,761 research outputs found
Phonon Squeezing in a Superconducting Molecular Transistor
Josephson transport through a single molecule or carbon nanotube is
considered in the presence of a local vibrational mode coupled to the
electronic charge. The ground-state solution is obtained exactly in the limit
of a large superconducting gap, and is extended to the general case by
variational analysis. Coherent charge fluctuations are entangled with
non-classical phonon states. The Josephson current induces squeezing of the
phonon mode, which is controlled by the superconducting phase difference and by
the junction asymmetry. Optical probes of non-classical phonon states are
briefly discussed
Health Outcomes And The Cost-Quality Trade-Off In Health Care: Empirical Study Of OECD Countries
This study applies multivariate regression analysis to cross-section data of 30 OECD countries to determine if there is a trade-off between health care cost and the quality of the health system on one hand, and better health outcomes on the other. It also investigates whether a higher quality health system leads to superior health outcomes. The empirical results provide positive answers to the above two questions. Indices of responsiveness, fairness or accessibility, and overall efficiency of the health system developed by the World Health Organization were used in this study to measure health system quality. The rate of infant mortality and a disability-free or healthy life expectancy measure developed by the WHO are used as indicators of health outcomes. The empirical models control for the effects of cross-country differences in literacy level and health-risk or lifestyle. The study finds evidence that the more responsive and accessible the country’s health system is, the longer is the healthy life expectancy of its people. Moreover, the more accessible and efficient the country’s health system is, the lower is the rate of infant mortality
A Brief Introduction to Chiral Perturbation Theory
A brief introduction to the subject of chiral perturbation theory (pt)
is presented, including a discussion of effective field theory and applications
of pt in the arena of purely mesonic interactions as well as in the sector.Comment: 15 pages, talk given at TAPS detector workshop, Rez, Czech Republic,
Sept. 1999, to be published in Czech. J. Phy
Pion and Kaon Polarizabilities and Radiative Transitions
CERN COMPASS plans measurements of gamma-pi and gamma-K interactions using
50-280 GeV pion (kaon) beams and a virtual photon target. Pion (kaon)
polarizabilities and radiative transitions will be measured via Primakoff
effect reactions such as pi+gamma->pi'+gamma and pi+gamma->meson. The former
can test a precise prediction of chiral symmetry; the latter for
pi+gamma->a1(1260) is important for understanding the polarizability. The
radiative transition of a pion to a low mass two-pion system, pi+gamma->pi+pi0,
can also be studied to measure the chiral anomaly amplitude F(3pi)
(characterizing gamma->3pi), arising from the effective Chiral Lagrangian. We
review here the motivation for the above physics program. We describe the beam,
target, detector, and trigger requirements for these experiments. We also
describe FNAL SELEX attempts to study related physics via the interaction of
600 GeV pions with target electrons. Data analysis in progress aims to identify
the reactions pi+e->pi'+e'+pi0 related to the chiral anomaly, and
pi+e->pi'+e'+gamma related to pion polarizabilities.Comment: 16 pages, 6 figures, Latex Springer-Verlag style Tel Aviv U. Preprint
TAUP-2469-97, Contribution to the Workshop on Chiral Dynamics Theory and
Experiment, U. of Mainz, Sept. 1-5, 1997, to be published in Springer-Verlag,
Eds. A. Bernstein, Th. Walcher, 199
Phase diagram of the one dimensional anisotropic Kondo-necklace model
The one dimensional anisotropic Kondo-necklace model has been studied by
several methods. It is shown that a mean field approach fails to gain the
correct phase diagram for the Ising type anisotropy. We then applied the spin
wave theory which is justified for the anisotropic case. We have derived the
phase diagram between the antiferromagnetic long range order and the Kondo
singlet phases. We have found that the exchange interaction (J) between the
itinerant spins and local ones enhances the quantum fluctuations around the
classical long range antiferromagnetic order and finally destroy the ordered
phase at the critical value, J_c. Moreover, our results show that the onset of
anisotropy in the XY term of the itinerant interactions develops the
antiferromagnetic order for J<J_c. This is in agreement with the qualitative
feature which we expect from the symmetry of the anisotropic XY interaction. We
have justified our results by the numerical Lanczos method where the structure
factor at the antiferromagnetic wave vector diverges as the size of system goes
to infinity.Comment: 9 pages and 9 eps figure
Effects of dimensionality and anisotropy on the Holstein polaron
We apply weak-coupling perturbation theory and strong-coupling perturbation
theory to the Holstein molecular crystal model in order to elucidate the
effects of anisotropy on polaron properties in D dimensions. The ground state
energy is considered as a primary criterion through which to study the effects
of anisotropy on the self-trapping transition, the self-trapping line
associated with this transition, and the adiabatic critical point. The effects
of dimensionality and anisotropy on electron-phonon correlations and polaronic
mass enhancement are studied, with particular attention given to the polaron
radius and the characteristics of quasi-1D and quasi-2D structures.
Perturbative results are confirmed by selected comparisons with variational
calculations and quantum Monte Carlo data
Classical Physics and Quantum Loops
The standard picture of the loop expansion associates a factor of h-bar with
each loop, suggesting that the tree diagrams are to be associated with
classical physics, while loop effects are quantum mechanical in nature. We
discuss examples wherein classical effects arise from loop contributions and
display the relationship between the classical terms and the long range effects
of massless particles.Comment: 15 pages, 3 figure
Hall resistance in the hopping regime, a "Hall Insulator"?
The Hall conductivity and resistivity of strongly localized electrons at low
temperatures and at small magnetic fields are obtained. It is found that the
results depend on whether the conductivity or the resistivity tensors are
averaged to obtain the macroscopic Hall resistivity. In the second case the
Hall resistivity always {\it diverges} exponentially as the temperature tends
to zero. But when the Hall resistivity is derived from the averaged
conductivity, the resulting temperature dependence is sensitive to the disorder
configuration. Then the Hall resistivity may approach a constant value as . This is the Hall insulating behavior. It is argued that for strictly dc
conditions, the transport quantity that should be averaged is the resistivity.Comment: Late
Observation of the Holstein shift in high superconductors with thermal modulation reflectometry
We use the experimental technique of thermal modulation reflectometry to
study the relatively small temperature dependence of the optical conductivity
of superconductors. Due to a large cancellation of systematic errors, this
technique is shown to a be very sensitive probe of small changes in
reflectivity. We analyze thermal modulation reflection spectra of single
crystals and epitaxially grown thin films of YBaCuO and
obtain the function in the normal state, as well as
the superconductivity induced changes in reflectivity. We present detailed
model calculations, based on the Eliashberg-Migdal extension of the BCS model,
which show good qualitative and quantitative agreement with the experimental
spectra. VSGD.93.12.thComment: 6 pages, figures on request. Revtex, version 2, Materials Science
Center Internal Report Number VSGD.93.12.t
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