8,486 research outputs found

    Photometry of 40 LMC Cepheids

    Get PDF
    We present V and I_c CCD photometry for 40 LMC Cepheids at 1 to 3 epochs. This represents a significant increase in the number of LMC Cepheids with II-band data, and, as we show, is a useful addition to the sample which can be used to calibrate the period--luminosity relations in these important bands

    Neutral kaon mixing beyond the standard model with nf=2+1 chiral fermions

    Get PDF
    We compute the hadronic matrix elements of the four-quark operators needed for the study of neutral kaon mixing beyond the Standard Model (SM). We use nf=2+1 flavours of domain-wall fermions (DWF) which exhibit good chiral-flavour symmetry. The renormalization is performed non-perturbatively through the RI-MOM scheme and our results are converted perturbatively to MSbar. The computation is performed on a single lattice spacing a=0.086 fm with a lightest unitary pion mass of 290 MeV. The various systematic errors, including the discretisation effects, are estimated and discussed. Our results confirm a previous quenched study, where large ratios of non-SM to SM matrix elements were obtained.Comment: 5 pages, 4 figures, 1 table. v2 paper version, R3 and B3 corrected, conversion to 2GeV added, references adde

    Spousal Labor Market Effects from Government Health Insurance: Evidence from a Veterans Affairs Expansion

    Get PDF
    Although government expansion of health insurance to older workers leads to labor supply reductions for recipients, there may be spillover effects on the labor supply of affected spouses who are not covered by the programs. In the simplest model, health insurance on the job is paid for in terms of lower compensation on the job. Receiving health insurance exogenous to employment is akin to a positive income shock for the household, causing total household labor supply to drop. However, it is not clear within the household whether this decrease in labor supply will be borne by both spouses or by a specific spouse. We use a mid-1990s expansion of health insurance for U.S. veterans to provide evidence on the effects of expanding health insurance availability on the labor supply of spouses. Using data from the Current Population Survey, we employ a difference-in-differences strategy to compare the labor market behavior of the wives of older male veterans and non-veterans before and after the VA health benefits expansion to test the impact of public health insurance on these spouses. Our findings suggest that although household labor supply may decrease because of the income effect, the more flexible labor supply of wives allows the wife’s labor supply to increase, particularly for those with lower education levels.Health Economics, Labor force participation

    Accuracy of numerical relativity waveforms from binary neutron star mergers and their comparison with post-Newtonian waveforms

    Get PDF
    We present numerical relativity simulations of nine-orbit equal-mass binary neutron star covering the quasicircular late inspiral and merger. The extracted gravitational waveforms are analyzed for convergence and accuracy. Second order convergence is observed up to contact, i.e. about 3-4 cycles to merger; error estimates can be made up to this point. The uncertainties on the phase and the amplitude are dominated by truncation errors and can be minimized to 0.13 rad and less then 1%, respectively, by using several simulations and extrapolating in resolution. In the latter case finite-radius extraction uncertainties become a source of error of the same order and have to be taken into account. The waveforms are tested against accuracy standards for data analysis. The uncertainties on the waveforms are such that accuracy standards are generically not met for signal-to-noise ratios relevant for detection, except for some best cases using extrapolation from several runs. A detailed analysis of the errors is thus imperative for the use of numerical relativity waveforms from binary neutron stars in quantitative studies. The waveforms are compared with the post-Newtonian Taylor T4 approximants both for point-particle and including the analytically known tidal corrections. The T4 approximants accumulate significant phase differences of 2 rad at contact and 4 rad at merger, underestimating the influence of finite size effects. Tidal signatures in the waveforms are thus important at least during the last six orbits of the merger process.Comment: Physical Review D (Vol.85, No.10) 201

    Electron heating mechanisms in dual frequency capacitive discharges

    Get PDF
    We discuss electron heating mechanisms in the sheath regions of dual-frequency capacitive discharges, with the twin aims of identifying the dominant mechanisms and supplying closed-form expressions from which the heating power can be estimated. We show that the heating effect produced by either Ohmic or collisionless heating is much larger when the discharge is excited by a superposition of currents at two frequencies than if either current had acted alone. This coupling effect occurs because the lower frequency current, while not directly heating the electrons to any great extent, strongly affects the spatial structure of the discharge in the sheath regions

    Opening the Rome-Southampton window for operator mixing matrices

    Full text link
    We show that the running of operators which mix under renormalization can be computed fully non-perturbatively as a product of continuum step scaling matrices. These step scaling matrices are obtained by taking the "ratio" of Z matrices computed at different energies in an RI-MOM type scheme for which twisted boundary conditions are an essential ingredient. Our method allows us to relax the bounds of the Rome-Southampton window. We also explain why such a method is important in view of the light quark physics program of the RBC-UKQCD collaborations. To illustrate our method, using n_f=2+1 domain-wall fermions, we compute the non-perturbative running matrix of four-quark operators needed in K->pipi decay and neutral kaon mixing. Our results are then compared to perturbation theory.Comment: 8 pages, 7 figures. v2: PRD version, minor changes and few references adde

    Spousal Labor Market Effects from Government Health Insurance: Evidence from a Veterans Affairs Expansion

    Get PDF
    Although government expansion of health insurance to older workers leads to labor supply reductions for recipients, there may be spillover effects on the labor supply of affected spouses who are not covered by the programs. In the simplest model, health insurance on the job is paid for in terms of lower compensation on the job. Receiving health insurance exogenous to employment is akin to a positive income shock for the household, causing total household labor supply to drop. However, it is not clear within the household whether this decrease in labor supply will be borne by both spouses or by a specific spouse. We use a mid-1990s expansion of health insurance for U.S. veterans to provide evidence on the effects of expanding health insurance availability on the labor supply of spouses. Using data from the Current Population Survey, we employ a difference-in-differences strategy to compare the labor market behavior of the wives of older male veterans and non-veterans before and after the VA health benefits expansion to test the impact of public health insurance on these spouses. Our findings suggest that although household labor supply may decrease because of the income effect, the more flexible labor supply of wives allows the wife’s labor supply to increase, particularly for those with lower education levels

    Proton lifetime bounds from chirally symmetric lattice QCD

    Full text link
    We present results for the matrix elements relevant for proton decay in Grand Unified Theories (GUTs). The calculation is performed at a fixed lattice spacing a^{-1}=1.73(3) GeV using 2+1 flavors of domain wall fermions on lattices of size 16^3\times32 and 24^3\times64 with a fifth dimension of length 16. We use the indirect method which relies on an effective field theory description of proton decay, where we need to estimate the low energy constants, \alpha = -0.0112(25) GeV^3 and \beta = 0.0120(26) GeV^3. We relate these low energy constants to the proton decay matrix elements using leading order chiral perturbation theory. These can then be combined with experimental bounds on the proton lifetime to bound parameters of individual GUTs.Comment: 17 pages, 9 Figure
    corecore