Infinite Volume and Continuum Limits of the Landau-Gauge Gluon Propagator

We extend a previous improved action study of the Landau gauge gluon propagator, by using a variety of lattices with spacings from $a = 0.17$ to 0.41 fm, to more fully explore finite volume and discretization effects. We also extend a previously used technique for minimizing lattice artifacts, the appropriate choice of momentum variable or ``kinematic correction'', by considering it more generally as a ``tree-level correction''. We demonstrate that by using tree-level correction, determined by the tree-level behavior of the action being considered, it is possible to obtain scaling behavior over a very wide range of momenta and lattice spacings. This makes it possible to explore the infinite volume and continuum limits of the Landau-gauge gluon propagator.Comment: 24 pages RevTex, 18 figures; Responses to referee comments, minor change

Stability of Surface Complexes Formed at the TiO2/Water Interface

TiO2 surface complexation by bidentate organic ligands is analysed in terms of the ligand Brønstead and Lewis basicities. The complexation and basicity constants comply with linear Gibbs Energy relationships (LGERs). For dicarboxylic acids, the surface chelate bond makes an approximately constant contribution to the stability. The proton transfer to the surface modulates the pH dependence of stability. A correlation exists between the surface complexation constant of the neutral acid H2L and the ligand first acidity constant. On the other hand, the surface complexation constants of dianions L2- of cathecols and aminophenols are positively correlated with the ligand second acidity constant. Apparent stability is determined by the competition of H+ and surface metal ions for the ligand. Stability trends are strongly influenced by the Brønstead acid base reaction between the acid ligands H2L and the surface, whereas the stability of the surface chelate contributes to the overall stability

Comparing the Ancient Star Formation Histories of the Magellanic Clouds

We present preliminary results from a new HST archival program aimed at tightly constraining the ancient (>4 Gyr ago) star formation histories (SFHs) of the field populations of the SMC and LMC. We demonstrate the quality of the archival data by constructing HST/WFPC2-based color-magnitude diagrams (CMDs; M_{F555W} ~ +8) for 7 spatially diverse fields in the SMC and 8 fields in the LMC. The HST-based CMDs are >2 magnitudes deeper than any from ground based observations, and are particularly superior in high surface brightness regions, e.g., the LMC bar, which contain a significant fraction of star formation and are crowding limited from ground based observations. To minimize systematic uncertainties, we derive the SFH of each field using an identical maximum likelihood CMD fitting technique. We then compute an approximate mass weighted average SFH for each galaxy. We find that both galaxies lack a dominant burst of early star formation, which suggests either a suppression or an under-fueling of early star formation. From 10-12 Gyr ago, the LMC experienced a period of enhanced stellar mass growth relative to the SMC. Similar to some previous studies, we find two notable peaks in the SFH of the SMC at ~4.5 and 9 Gyr ago, which could be due to repeated close passages with the LMC, implying an interaction history that has persisted for at least 9 Gyr. We find little evidence for strong periodic behavior in the lifetime SFHs of both MCs, suggesting that repeated encounters with the Milky Way are unlikely. Beginning ~3.5 Gyr ago, both galaxies show increases in their SFHs, in agreement with previous studies, and thereafter, track each other remarkably well. (abridged)Comment: 9 pages, 5 Figures, Accepted for Publication in MNRA

Perturbative renormalization factors in domain-wall QCD with improved gauge actions

We evaluate renormalization factors of the domain-wall fermion system with various improved gauge actions at one loop level. The renormalization factors are calculated for quark wave function, quark mass, bilinear quark operators, three- and four-quark operators in modified minimal subtraction (MS-bar) scheme with the dimensional reduction(DRED) as well as the naive dimensional regularization(NDR). We also present detailed results in the mean field improved perturbation theory.Comment: 44 page

The H-alpha Light Curves and Spatial Distribution of Novae in M81

We present the results of a preliminary H-alpha survey of M81 for novae conducted over a 5 month interval using the 5' field of view camera (WFCAM) on the Calypso Telescope at Kitt Peak, AZ. We observed M81 nearly every clear night during this interval, covering the entire galaxy, and discovered 12 novae. Our comprehensive time coverage allowed us to produce the most complete set of H-alpha light curves for novae in M81 to date. A raw nova rate for M81 gives 23 yr^-1 which, because of the nature of our survey, is a hard lower limit. An analysis of the completeness in our survey gives a corrected nova rate of 30 yr^-1. This agrees well with the rate of 33 (+13,-8) yr^-1, derived from Monte Carlo simulations using nova light curves and survey frame limits. The spatial distribution of the novae we discovered follows the bulge light much better than the disk or total light according to Kolmogorov - Smirnov tests of their radial distributions. The asymmetry in the distribution of novae across the major axis line of M81 implies a bulge-to-disk nova ratio of > 9 and supports the idea that novae originate primarily in older stellar populations.Comment: 41 pages, 10 figures, and 7 tables, accepted, to appear in AJ, Feb 2004, updated raw and completeness corrected nova rate