Potentials between heavy-light mesons from lattice and inverse scattering theory

We extend our investigation of heavy-light meson-meson interactions to a system consisting of a heavy-light meson and the corresponding antiparticle. An effective potential is obtained from meson-antimeson Green-functions computed in a quenched simulation with staggered fermions. Comparisons with a simulation using an $O(a^2)$ tree-level and tadpole improved gauge action and a full QCD simulation show that lattice discretization errors and dynamical quarks have no drastic influence. Calculations from inverse scattering theory propose a similar shape for $K\bar{K}$ potentials.Comment: 3 pages, 5 EPS figures, Poster presented at "Lattice'97", to appear in the proceeding

Numerical solution of the color superconductivity gap in a weak coupling constant

We present the numerical solution of the full gap equation in a weak coupling constant $g$. It is found that the standard approximations to derive the gap equation to the leading order of coupling constant are essential for a secure numerical evaluation of the logarithmic singularity with a small coupling constant. The approximate integral gap equation with a very small $g$ should be inverted to a soft integral equation to smooth the logarithmic singularity near the Fermi surface. The full gap equation is solved for a rather large coupling constant $g\ge 2.0$. The approximate and soft integral gap equations are solved for small $g$ values. When their solutions are extrapolated to larger $g$ values, they coincide the full gap equation solution near the Fermi surface. Furthermore, the analytical solution matches the numerical one up to the order one O(1). Our results confirm the previous estimates that the gap energy is of the order tens to 100 MeV for the chemical potential $\mu\le 1000$ MeV. They also support the validity of leading approximations applied to the full gap equation to derive the soft integral gap equation and its analytical solution near the Fermi surface.Comment: 7 pages+ 6 figs, Stanford, Frankfurt and Bethlehe

Gluons, tadpoles, and color neutrality in a two-flavor color superconductor

Considering cold, dense quark matter with two massless quark flavors, we demonstrate how, in a self-consistent calculation in the framework of QCD, the condensation of Cooper pairs induces a non-vanishing background color field. This background color field has precisely the right magnitude to cancel tadpole contributions and thus ensures overall color neutrality of the two-flavor color superconductor.Comment: 10 pages, contribution to the proceedings of the Erice school "Heavy-Ion Collisions from Nuclear to Quark Matter" 200

Positivity of High Density Effective Theory

We show that the effective field theory of low energy modes in dense QCD has positive Euclidean path integral measure. The complexity of the measure of QCD at finite chemical potential can be ascribed to modes which are irrelevant to the dynamics at sufficiently high density. Rigorous inequalities follow at asymptotic density. Lattice simulation of dense QCD should be possible using the quark determinant calculated in the effective theory.Comment: 10 pages, Revised version, to appear in Rapid Communications of Physical Review

A quark action for very coarse lattices

We investigate a tree-level O(a^3)-accurate action, D234c, on coarse lattices. For the improvement terms we use tadpole-improved coefficients, with the tadpole contribution measured by the mean link in Landau gauge. We measure the hadron spectrum for quark masses near that of the strange quark. We find that D234c shows much better rotational invariance than the Sheikholeslami-Wohlert action, and that mean-link tadpole improvement leads to smaller finite-lattice-spacing errors than plaquette tadpole improvement. We obtain accurate ratios of lattice spacings using a convenient ``Galilean quarkonium'' method. We explore the effects of possible O(alpha_s) changes to the improvement coefficients, and find that the two leading coefficients can be independently tuned: hadron masses are most sensitive to the clover coefficient, while hadron dispersion relations are most sensitive to the third derivative coefficient C_3. Preliminary non-perturbative tuning of these coefficients yields values that are consistent with the expected size of perturbative corrections.Comment: 22 pages, LaTe

Neutron stars and the transition to color-superconducting quark matter

We explore the relevance of color superconductivity inside a possible quark matter core for the bulk properties of neutron stars. For the quark phase we use an Nambu--Jona-Lasinio (NJL) type model, extended to include diquark condensates. For the hadronic phase, a microscopic many-body model is adopted, with and without strangeness content. In our calculations, a sharp boundary is assumed between the hadronic and the quark phases. For NJL model parameters fitted to vacuum properties we find that no star with a pure quark core does exist. Nevertheless the presence of color superconducting phases can lower the neutron star maximum mass substantially. In some cases, the transition to quark matter occurs only if color superconductivity is present. Once the quark phase is introduced, the value of the maximum mass stays in any case below the value of two solar masses.Comment: 11 pages, 3 figures, v2: minor corrections in the text, layout of the figures improved, references added, v3: transition densities from hadronic to quark matter added, version accepted for publication in PL

U.S. Air Force Maintenance Group Aerial Ports: Strengths, Challenges, Opportunities, and Threats

In 2005 the Base Closure Realignment Commission and Secretary of Defense recommended joint basing; as an indirect result starting in 2009 and culminating the following year, Charleston, Dover, McChord, McGuire, and Travis maintenance groups (MXG) took command of aerial port squadrons (APS). Various entities have discussed at length the impact; however, there did not appear to be a documented hard look into the strengths, challenges, opportunities, and threats (SCOTs) which emerged. This study utilized the Delphi method to flesh out MXG APS SCOTs by anonymously surveying MXG and APS experts through three panel rounds. This study discovered and documented 24 SCOTs and viewed them through the Competing Values Framework (CVF) theoretical lens. The majority of the panel’s inputs concerning maintenance and aerial port entities fell on opposing sides of the CVF; which may explain why the panel, consisting of maintenance and APS leaders, did not reach strong consensus in two out of four SCOT categories. This study proposes creating a wing or standalone group to house the five aerial ports or altering the MXG title to be more representative of all squadrons assigned and ensuring at least one logistics readiness officer or aerial porter is on each MXG leadership team