1,615 research outputs found
Path Integral Monte Carlo Approach to the U(1) Lattice Gauge Theory in (2+1) Dimensions
Path Integral Monte Carlo simulations have been performed for U(1) lattice
gauge theory in (2+1) dimensions on anisotropic lattices. We extractthe static
quark potential, the string tension and the low-lying "glueball" spectrum.The
Euclidean string tension and mass gap decrease exponentially at weakcoupling in
excellent agreement with the predictions of Polyakov and G{\" o}pfert and Mack,
but their magnitudes are five times bigger than predicted. Extrapolations are
made to the extreme anisotropic or Hamiltonian limit, and comparisons are made
with previous estimates obtained in the Hamiltonian formulation.Comment: 12 pages, 16 figure
Pedestrian Solution of the Two-Dimensional Ising Model
The partition function of the two-dimensional Ising model with zero magnetic
field on a square lattice with m x n sites wrapped on a torus is computed
within the transfer matrix formalism in an explicit step-by-step approach
inspired by Kaufman's work. However, working with two commuting representations
of the complex rotation group SO(2n,C) helps us avoid a number of unnecessary
complications. We find all eigenvalues of the transfer matrix and therefore the
partition function in a straightforward way.Comment: 10 pages, 2 figures; eqs. (101) and (102) corrected, files for fig. 2
fixed, minor beautification
RETRATO DE MUJER DE LUTO [Material gráfico]
Copia digital. Madrid : Ministerio de Educación, Cultura y Deporte. Subdirección General de Coordinación Bibliotecaria, 201
The Hamiltonian limit of (3+1)D SU(3) lattice gauge theory on anisotropic lattices
The extreme anisotropic limit of Euclidean SU(3) lattice gauge theory is
examined to extract the Hamiltonian limit, using standard path integral Monte
Carlo (PIMC) methods. We examine the mean plaquette and string tension and
compare them to results obtained within the Hamiltonian framework of Kogut and
Susskind. The results are a significant improvement upon previous Hamiltonian
estimates, despite the extrapolation procedure necessary to extract
observables. We conclude that the PIMC method is a reliable method of obtaining
results for the Hamiltonian version of the theory. Our results also clearly
demonstrate the universality between the Hamiltonian and Euclidean formulations
of lattice gauge theory. It is particularly important to take into account the
renormalization of both the anisotropy, and the Euclidean coupling ,
in obtaining these results.Comment: 10 pages, 11 figure
Representation in Westminster in the 1990s : The ghost of Edmund Burke
Why are 'trustee' notions of representation still invoked in the UK House of Commons in the 1990s? In answering this question this article analyses the premises of Burkean theory and the arguments that these premises are of little relevance in the late twentieth century. Despite these dismissals of trusteeship, Burkean ideas are still articulated in the Commons some 200 years after they were first voiced. The idea of trusteeship can prove extremely useful to justify the actions of representatives when those actions conflict with constituency 'opinion', party policy or the wishes of interest groups. Examples of the occasions when Burkean notions have been invoked in the 1990s are provided
Subsoiling and surface tillage effects on soil physical properties and forage oat stand and yield
Much of New Zealand's agriculture integrates animal and crop production on poorly drained,
easily compacted soils. We hypothesized that soil properties affecting forage oat (Avena sativa,
cv Awapuni) establishment on land compacted by 15 years of conventional cropping might be
influenced by various subsoiling and surface tillage combinations. Plots on a Moutoa silty clay
(Typic Haplaquoil) were paraplowed (P), deep subsoiled (V), shallow subsoiled (5), or were left
as non-subsoiled controls (C). Subsequently, the surface 15 cm was surface-tilled (T) using a
power rotary-tiller and firmed with a Cambridge roller or were not tilled (N). Oats were then sown
with a cross-slot drill. Subsoiling greatly reduced soil strength. Cone indices showed disruption to
40cm with P, 36 cm for V, and 30 cm for S. Approximately 60% of profile cone indices to a depth
of 0.5 m from subsoiled treatments were less than 1.5 MPa, compared to approximately 30% for C.
T slightly improved strength distribution in non-subsoiled controls but had little effect in subsoiled
treatments. Subsoiling without T continued to show improved profile cone index cumulative
frequency 233 days after subsoiling, Subsoiling after T in this high rainfall climate eliminated
most of the separation in cumulative frequency of soil profile cone index values by two weeks
after T. T reduced emergence from 142 to 113 plants per square meter and reduced yield from
5318 to 3679 kg ha-1. Forage yield increased from 3974 to 4674 kg ha-1 with subsoiling. Soil
porosity, saturated and slightly unsaturated hydraulic conductivities (KSAT and K_40 ) and air
permeability were highly variable but generally increased with subsoiling. Oxygen diffusion rate
(ODR) (using Pt microelectrodes) was also variable, but N and C treatments had consistently
lower ODRs than T or subsoiled treatments. Generally, subsoiling without T produced better soil
conditions and oat crop performance than the prevailing New Zealand practice of T without subsoiling
Impact of analytic provenance in genome analysis
Many computational methods are available for assembly and annotation of newly sequenced microbial genomes. However, when new genomes are reported in the literature, there is frequently very little critical analysis of choices made during the sequence assembly and gene annotation stages. These choices have a direct impact on the biologically relevant products of a genomic analysis - for instance identification of common and differentiating regions among genomes in a comparison, or identification of enriched gene functional categories in a specific strain. Here, we examine the outcomes of different assembly and analysis steps in typical workflows in a comparison among strains of Vibrio vulnificus
Molecular Dynamics Study of Bamboo-like Carbon Nanotube Nucleation
MD simulations based on an empirical potential energy surface were used to
study the nucleation of bamboo-like carbon nanotubes (BCNTs). The simulations
reveal that inner walls of the bamboo structure start to nucleate at the
junction between the outer nanotube wall and the catalyst particle. In
agreement with experimental results, the simulations show that BCNTs nucleate
at higher dissolved carbon concentrations (i.e., feedstock pressures) than
those where non-bamboolike carbon nanotubes are nucleated
Metastability and Transient Effects in Vortex Matter Near a Decoupling Transition
We examine metastable and transient effects both above and below the
first-order decoupling line in a 3D simulation of magnetically interacting
pancake vortices. We observe pronounced transient and history effects as well
as supercooling and superheating between the 3D coupled, ordered and 2D
decoupled, disordered phases. In the disordered supercooled state as a function
of DC driving, reordering occurs through the formation of growing moving
channels of the ordered phase. No channels form in the superheated region;
instead the ordered state is homogeneously destroyed. When a sequence of
current pulses is applied we observe memory effects. We find a ramp rate
dependence of the V(I) curves on both sides of the decoupling transition. The
critical current that we obtain depends on how the system is prepared.Comment: 10 pages, 15 postscript figures, version to appear in PR
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