Projector operators for the no-core shell model

Projection operators for the use within ab initio no-core shell model, are suggested.Comment: 3 page

Charge dynamics in the phase string model for high-Tc superconductors

An understanding of the anomalous charge dynamics in the high-Tc cuprates is obtained based on a model study of doped Mott insulators. The high-temperature optical conductivity is found to generally have a two-component structure: a Drude like part followed by a mid-infrared band. The scattering rate associated with the Drude part exhibits a linear-temperature dependence over a wide range of high temperature, while the Drude term gets progressively suppressed below a characteristic energy of magnetic origin as the system enters the pseudogap phase. The high-energy optical conductivity shows a resonancelike feature in an underdoped case and continuously evolves into a 1/\omega tail at higher doping, indicating that they share the same physical origin. In particular, such a high-energy component is closely correlated with the \omega-peak structure of the density-density correlation function at different momenta, in systematic consistency with exact diagonalization results based on the t-J model. The underlying physics is attributed to the high-energy spin-charge separation in the model, in which the "mode coupling" responsible for the anomalous charge properties is not between the electrons and some collective mode but rather between new charge carriers, holons, and a novel topological gauge field controlled by spin dynamics, as the consequence of the strong short-range electron-electron Coulomb repulsion in the doped Mott insulator.Comment: 19 pages, 13 figures; final version to appear in Phys. Rev.

Understanding the Economic Consequences of Shifting Trends in Population Health

The public economic burden of shifting trends in population health remains uncertain. Sustained increases in obesity, diabetes, and other diseases could reduce life expectancy – with a concomitant decrease in the public-sector’s annuity burden – but these savings may be offset by worsening functional status, which increases health care spending, reduces labor supply, and increases public assistance. Using a microsimulation approach, we quantify the competing public-finance consequences of shifting trends in population health for medical care costs, labor supply, earnings, wealth, tax revenues, and government expenditures (including Social Security and income assistance). Together, the reduction in smoking and the rise in obesity have increased net public-sector liabilities by $430bn, or approximately 4% of the current debt burden. Larger effects are observed for specific public programs: annual spending is 10% higher in the Medicaid program, and 7% higher for Medicare.disability, health care costs, social security, microsimulation

International Differences in Longevity and Health and their Economic Consequences

In 1975, 50 year-old Americans could expect to live slightly longer than their European counterparts. By 2005, American life expectancy at that age has diverged substantially compared to Europe. We find that this growing longevity gap is primarily the symptom of real declines in the health of near-elderly Americans, relative to their European peers. In particular, we use a microsimulation approach to project what US longevity would look like, if US health trends approximated those in Europe. We find that differences in health can explain most of the growing gap in remaining life expectancy. In addition, we quantify the public finance consequences of this deterioration in health. The model predicts that gradually moving American cohorts to the health status enjoyed by Europeans could save up to $1.1 trillion in discounted total health expenditures from 2004 to 2050.disability, mortality, international comparisons, microsimulation

Carbon Nanotubes in Helically Modulated Potentials

We calculate effects of an applied helically symmetric potential on the low energy electronic spectrum of a carbon nanotube in the continuum approximation. The spectrum depends on the strength of this potential and on a dimensionless geometrical parameter, P, which is the ratio of the circumference of the nanotube to the pitch of the helix. We find that the minimum band gap of a semiconducting nanotube is reduced by an arbitrarily weak helical potential, and for a given field strength there is an optimal P which produces the biggest change in the band gap. For metallic nanotubes the Fermi velocity is reduced by this potential and for strong fields two small gaps appear at the Fermi surface in addition to the gapless Dirac point. A simple model is developed to estimate the magnitude of the field strength and its effect on DNA-CNT complexes in an aqueous solution. We find that under typical experimental conditions the predicted effects of a helical potential are likely to be small and we discuss several methods for increasing the size of these effects.Comment: 12 pages, 10 figures. Accepted for publication in Physical Review B. Image quality reduced to comply with arxiv size limitation

Spin singlet pairing in the superconducting state of NaxCoO2\cdot1.3H2O: evidence from a ^{59}Co Knight shift in a single crystal

We report a ^{59}Co Knight shift measurement in a single crystal of the cobalt oxide superconductor Na_{x}CoO_2\cdot1.3H_2O (T_c=4.25 K). We find that the shift due to the spin susceptibility, K^s, is substantially large and anisotropic, with the spin shift along the a-axis K^s_a being two times that along the c-axis K^s_c. The shift decreases with decreasing temperature (T) down to T\sim100 K, then becomes a constant until superconductivity sets in. Both K^s_a and K^s_c decrease below T_c. Our results indicate unambiguously that the electron pairing in the superconducting state is in the spin singlet form.Comment: 4 pages, 5 figure

Generic nodeless Larkin Ovchinnikov states due to singlet-triplet mixing

Larkin-Ovchinnikov (LO) states typically have a singlet-gap that vanishes along real-space lines. These real-space nodes lead to Andreev midgap states which can serve as a signature of LO pairing. We show that at these nodes, an odd-parity, spin-triplet component is always induced, leading to a nodeless LO phase. We find the two-dimensional weak coupling, clean limit s-wave phase diagram when this spin-triplet part is included. The triplet component is large and increases the stability of the FFLO phase. We also show that the spin-triplet contribution pushes the midgap states away from zero energy. Finally, we show how our results can be explained phenomenologically though Lifshitz invariants. These invariants provide a simple approach to understand the role of unconventional pairing states, spin-orbit coupling, and inhomogeneous mixed singlet-triplet states that are not due to a FFLO instability. We discuss our results in the context of organic superconductors.Comment: 4 pages, 4 figure

Handling Attrition in Longitudinal Studies: The Case for Refreshment Samples

Panel studies typically suffer from attrition, which reduces sample size and can result in biased inferences. It is impossible to know whether or not the attrition causes bias from the observed panel data alone. Refreshment samples - new, randomly sampled respondents given the questionnaire at the same time as a subsequent wave of the panel - offer information that can be used to diagnose and adjust for bias due to attrition. We review and bolster the case for the use of refreshment samples in panel studies. We include examples of both a fully Bayesian approach for analyzing the concatenated panel and refreshment data, and a multiple imputation approach for analyzing only the original panel. For the latter, we document a positive bias in the usual multiple imputation variance estimator. We present models appropriate for three waves and two refreshment samples, including nonterminal attrition. We illustrate the three-wave analysis using the 2007-2008 Associated Press-Yahoo! News Election Poll.Comment: Published in at http://dx.doi.org/10.1214/13-STS414 the Statistical Science (http://www.imstat.org/sts/) by the Institute of Mathematical Statistics (http://www.imstat.org

Relaxation-to-creep transition of domain-wall motion in two- dimensional random-field Ising model with ac driving field

With Monte Carlo simulations, we investigate the relaxation dynamics with a domain wall for magnetic systems at the critical temperature. The dynamic scaling behavior is carefully analyzed, and a dynamic roughening process is observed. For comparison, similar analysis is applied to the relaxation dynamics with a free or disordered surfaceComment: 5 pages, 5 figure