The Improvement Program in Nonrelativistic Lattice QCD

Progress in the improvement program in nonrelativistic lattice QCD is outlined. The leading radiative corrections to the heavy-quark mass renormalization, energy shift, and two important kinetic coupling coefficients are presented. The reliability of tadpole-improved perturbation theory in determining the energy shift and mass renormalization is demonstrated.Comment: 3 pages in uuencoded-compressed-PostScript format, to appear in the Proceedings of LATTICE 93, Dallas, USA, October 1993; Edinburgh Preprint 93/53

The Heavy Quark Self-Energy in Nonrelativistic Lattice QCD

The heavy quark self-energy in nonrelativistic lattice QCD is calculated to $O(\alpha_s)$ in perturbation theory. An action which includes all spin-independent relativistic corrections to order $v^2$, where $v$ is the typical heavy quark velocity, and all spin-dependent corrections to order $v^4$ is used. The standard Wilson action and an improved multi-plaquette action are used for the gluons. Results for the mass renormalization, wavefunction renormalization, and energy shift are given; tadpole contributions are found to be large. A tadpole improvement scheme in which all link variables are rescaled by a mean-field factor is also studied. The effectiveness of this scheme in offsetting the large tadpole contributions to the heavy quark renormalization parameters is demonstrated.Comment: 28 pages, SLAC-PUB-598

Looking ahead: forecasting and planning for the longer-range future, April 1, 2, and 3, 2005

This repository item contains a single issue of the Pardee Conference Series, a publication series that began publishing in 2006 by the Boston University Frederick S. Pardee Center for the Study of the Longer-Range Future. This was the Center's spring Conference that took place during April 1, 2, and 3, 2005.The conference allowed for many highly esteemed scholars and professionals from a broad range of fields to come together to discuss strategies designed for the 21st century and beyond. The speakers and discussants covered a broad range of subjects including: long-term policy analysis, forecasting for business and investment, the National Intelligence Council Global Trends 2020 report, Europe’s transition from the Marshal plan to the EU, forecasting global transitions, foreign policy planning, and forecasting for defense

Unquenched Charmonium with NRQCD - Lattice 2000

We present results from a series of NRQCD simulations of the charmonium system, both in the quenched approximation and with n_f = 2 dynamical quarks. The spectra show evidence for quenching effects of ~10% in the S- and P-hyperfine splittings. We compare this with other systematic effects. Improving the NRQCD evolution equation altered the S-hyperfine by as much as 20 MeV, and we estimate radiative corrections may be as large as 40%.Comment: Lattice 2000 (Heavy Quark Physics

The Halo Occupation Distribution of Active Galactic Nuclei

Using a fully cosmological hydrodynamic simulation that self-consistently incorporates the growth and feedback of supermassive black holes and the physics of galaxy formation, we examine the effects of environmental factors (e.g., local gas density, black hole feedback) on the halo occupation distribution of low luminosity active galactic nuclei (AGN). We decompose the mean occupation function into central and satellite contribution and compute the conditional luminosity functions (CLF). The CLF of the central AGN follows a log-normal distribution with the mean increasing and scatter decreasing with increasing redshifts. We analyze the light curves of individual AGN and show that the peak luminosity of the AGN has a tighter correlation with halo mass compared to instantaneous luminosity. We also compute the CLF of satellite AGN at a given central AGN luminosity. We do not see any significant correlation between the number of satellites with the luminosity of the central AGN at a fixed halo mass. We also show that for a sample of AGN with luminosity above 10^42 ergs/s the mean occupation function can be modeled as a softened step function for central AGN and a power law for the satellite population. The radial distribution of AGN inside halos follows a power law at all redshifts with a mean index of -2.33 +/- 0.08. Incorporating the environmental dependence of supermassive black hole accretion and feedback, our formalism provides a theoretical tool for interpreting current and future measurements of AGN clustering.Comment: 14 pages, 11 figures, 2 Tables (Matches the MNRAS accepted version

Scaling of the B and D meson spectrum in lattice QCD

We give results for the $B$ and the $D$ meson spectrum using NRQCD on the lattice in the quenched approximation. The masses of radially and orbitally excited states are calculated as well as $S$-wave hyperfine and $P$-wave fine structure. Radially excited $P$-states are observed for the first time. Radial and orbital excitation energies match well to experiment, as does the strange-non-strange $S$-wave splitting. We compare the light and heavy quark mass dependence of various splittings to experiment. Our $B$-results cover a range in lattice spacings of more than a factor of two. Our $D$-results are from a single lattice spacing and we compare them to numbers in the literature from finer lattices using other methods. We see no significant dependence of physical results on the lattice spacing. PACS: 11.15.Ha 12.38.Gc 14.40.Lb 14.40.NdComment: 78 pages, 29 tables, 30 figures Revised version. Minor corrections to spelling and wordin

The detection of sub-solar mass dark matter halos

Dark matter halos of sub-solar mass are the first bound objects to form in cold dark matter theories. In this article, I discuss the present understanding of "microhalos'', their role in structure formation, and the implications of their potential presence, in the interpretation of dark matter experiments.Comment: 18 pages, 7 figures. Invited contribution to NJP Focus Issue on "Dark Matter and Particle Physics

CORE Technology and Exact Hamiltonian Real-Space Renormalization Group Transformations

The COntractor REnormalization group (CORE) method, a new approach to solving Hamiltonian lattice systems, is presented. The method defines a systematic and nonperturbative means of implementing Kadanoff-Wilson real-space renormalization group transformations using cluster expansion and contraction techniques. We illustrate the approach and demonstrate its effectiveness using scalar field theory, the Heisenberg antiferromagnetic chain, and the anisotropic Ising chain. Future applications to the Hubbard and t-J models and lattice gauge theory are discussed.Comment: 65 pages, 9 Postscript figures, uses epsf.st

Mannheimia haemolytica serovars associated with respiratory disease in cattle in Great Britain

BACKGROUND: Mannheimia haemolytica is commonly associated with respiratory disease in cattle worldwide as a cause of fibrinous pneumonia, bronchopneumonia and pleuritis. M. haemolytica is further subdivided into 12 serovars, however not all are considered to be pathogenic in cattle. The study aim was to determine the most common serovars of M. haemolytica associated with respiratory disease in cattle in Great Britain, which is currently unknown and could be useful information for clinicians when considering preventative strategies. RESULTS: One hundred four M. haemolytica isolates isolated from bovine clinical pathology and post-mortem samples from pneumonia cases between 2016 and 2018 were tested using a multiplex PCR assay to identify M. haemolytica serovars A1, A2 and A6. 46 isolates (44.2%) typed as M. haemolytica serovar A1, 31 (29.8%) as M. haemolytica serovar A2 and 18 isolates (17.3%) as M. haemolytica serovar A6. Nine isolates (8.7%) were not A1, A2 or A6 so were considered to belong to other serovars or were not typable. CONCLUSION: This study highlights the importance of M. haemolytica serovars other than A1 which may be responsible for respiratory disease in cattle and could help guide the veterinarian when making choices on preventative vaccination programmes. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12917-021-03121-3