Mixed Meson Masses with Domain-Wall Valence and Staggered Sea Fermions

Mixed action lattice calculations allow for an additive lattice spacing dependent mass renormalization of mesons composed of one sea and one valence quark, regardless of the type of fermion discretization methods used in the valence and sea sectors. The value of the mass renormalization depends upon the lattice actions used. This mixed meson mass shift is an important lattice artifact to determine for mixed action calculations; because it modifies the pion mass, it plays a central role in the low energy dynamics of all hadronic correlation functions. We determine the leading order, $\mathcal{O}(a^2)$, and next to leading order, $\mathcal{O}(a^2 m_\pi^2)$, additive mass shift of \textit{valence-sea} mesons for a mixed lattice action with domain-wall valence fermions and rooted staggered sea fermions, relevant to the majority of current large scale mixed action lattice efforts. We find that on the asqtad improved coarse MILC lattices, this additive mass shift is well parameterized in lattice units by $\Delta(am)^2 = 0.034(2) -0.06(2) (a m_\pi)^2$, which in physical units, using $a=0.125$ fm, corresponds to $\Delta(m)^2 = (291\pm 8 \textrm{MeV})^2 -0.06(2) m_\pi^2$. In terms of the mixed action effective field theory parameters, the corresponding mass shift is given by $a^2 \Delta_\mathrm{Mix} = (316 \pm 4 \textrm{MeV})^2$ at leading order plus next-to-leading order corrections including the necessary chiral logarithms for this mixed action calculation, determined in this work. Within the precision of our calculation, one can not distinguish between the full next-to-leading order effective field theory analysis of this additive mixed meson mass shift and the parameterization given above.Comment: 28 pages, 3 figures, 5 table

Algorithm based comparison between the integral method and harmonic analysis of the timing jitter of diode-based and solid-state pulsed laser sources

AbstractA comparison between two methods of timing jitter calculation is presented. The integral method utilizes spectral area of the single side-band (SSB) phase noise spectrum to calculate root mean square (rms) timing jitter. In contrast the harmonic analysis exploits the uppermost noise power in high harmonics to retrieve timing fluctuation. The results obtained show that a consistent timing jitter of 1.2ps is found by the integral method and harmonic analysis in gain-switched laser diodes with an external cavity scheme. A comparison of the two approaches in noise measurement of a diode-pumped Yb:KY(WO4)2 passively mode-locked laser is also shown in which both techniques give 2ps rms timing jitter

Low-Lying Eigenvalues of the Wilson-Dirac Operator

An exploratory study of the low-lying eigenvalues of the Wilson-Dirac operator and their corresonding eigenvectors is presented. Results for the eigenvalues from quenched and unquenched simulations are discussed. The eigenvectors are studied with respect to their localization properties in the quenched approximation for the cases of SU(2) and SU(3).Comment: Poster presented at LATTICE96(poster). 4 pages, LaTeX, fully coloured versions of Figs. 4 and 5 are included as separate gzipped PostScript files or can be obtained from http://www.desy.de/library/cgi-bin/showprep.pl?desy-rep%2F199615

Electronic structure and resistivity of the double exchange model

The double exchange (DE) model with quantum local spins S is studied; an equation of motion approach is used and decoupling approximations analogous to Hubbard's are made. Our approximate one-electron Green function G is exact in the atomic limit of zero bandwidth for all S and band filling n, and as n->0 reduces to a dynamical coherent potential approximation (CPA) due to Kubo; we regard our approximation as a many-body generalisation of Kubo's CPA. G is calculated self-consistently for general S in the paramagnetic state and for S=1/2 in a state of arbitrary magnetization. The electronic structure is investigated and four bands per spin are obtained centred on the atomic limit peaks of the spectral function. A resistivity formula appropriate to the model is derived from the Kubo formula and the paramagnetic state resistivity rho is calculated; insulating states are correctly obtained at n=0 and n=1 for strong Hund coupling. Our prediction for rho is much too small to be consistent with experiments on manganites so we agree with Millis et al that the bare DE model is inadequate. We show that the agreement with experiment obtained by Furukawa is due to his use of an unphysical density of states.Comment: 20 pages, 8 figures, submitted to J. Phys.: Condens. Matte

Probing the circulation of ring-shaped Bose-Einstein condensates

This paper reports the results of a theoretical and experimental study of how the initial circulation of ring-shaped Bose-Einstein condensates (BECs) can be probed by time-of-flight (TOF) images. We have studied theoretically the dynamics of a BEC after release from a toroidal trap potential by solving the 3D Gross-Pitaevskii (GP) equation. The trap and condensate characteristics matched those of a recent experiment. The circulation, experimentally imparted to the condensate by stirring, was simulated theoretically by imprinting a linear azimuthal phase on the initial condensate wave function. The theoretical TOF images were in good agreement with the experimental data. We find that upon release the dynamics of the ring--shaped condensate proceeds in two distinct phases. First, the condensate expands rapidly inward, filling in the initial hole until it reaches a minimum radius that depends on the initial circulation. In the second phase, the density at the inner radius increases to a maximum after which the hole radius begins slowly to expand. During this second phase a series of concentric rings appears due to the interference of ingoing and outgoing matter waves from the inner radius. The results of the GP equation predict that the hole area is a quadratic function of the initial circulation when the condensate is released directly from the trap in which it was stirred and is a linear function of the circulation if the trap is relaxed before release. These scalings matched the data. Thus, hole size after TOF can be used as a reliable probe of initial condensate circulation. This connection between circulation and hole size after TOF will facilitate future studies of atomtronic systems that are implemented in ultracold quantum gases.Comment: 9 pages, 9 figure

Carbohydrate intake and ketosis in self-sufficient multi-stage ultramarathon runners

Ultra-endurance athletes accumulate an energy deficit throughout their events and those competing in self-sufficient multi-stage races are particularly vulnerable due to load carriage considerations. Whilst urinary ketones have previously been noted in ultra-endurance exercise and attributed to insufficient carbohydrate (CHO) availability, not all studies have reported concomitant CHO intake. Our aim was to determine changes in blood glucose and β-hydroxybutyrate concentrations over five days (240 km) of a self-sufficient multi-stage ultramarathon in combination with quantification of energy and macronutrient intakes, estimated energy expenditure and evaluation of energy balance. Thirteen runners (8 male, 5 female, mean age 40 ± 8 years) participated in the study. Glucose and β-hydroxybutyrate were measured every day immediately post-running, and food diaries completed daily. CHO intakes of 301 ± 106 g·day−1 (4.3 ± 1.8 g·kg−1·day−1) were not sufficient to avoid ketosis (5-day mean β-hydroxybutyrate: 1.1 ± 0.6 mmol.L−1). Furthermore, ketosis was not attenuated even when CHO intake was high (9 g·kg−1·day−1). This suggests that competing in a state of ketosis may be inevitable during multi-stage events where load reduction is prioritised over energy provisions. Attenuating negative impacts associated with such a metabolic shift in athletes unaccustomed to CHO and energy restriction requires further exploration

Psychologists Collaborating With Clergy

If a patient adheres to religious values and practices, should the treating psychologist get input from a clergyperson? How frequent is clergy-psychologist collaboration? What obstacles impede such collaboration? An exploratory survey questionnaire was sent to 200 clergy, 200 psychologists interested in religious issues, and 200 psychologists selected without regard to religious interests or values. Four themes were assessed: types of collaborative activities, frequency of collaboration, obstacles to collaboration, and ways to enhance collaboration. Strategies for promoting clergy-psychologist collaboration include challenging unidirectional referral assumptions, building trust through proximity and familiarity, and considering the importance of shared values and beliefs