1,175 research outputs found
Finite temperature SU(2) gauge theory: critical coupling and universality class
We examine SU(2) gauge theory in 3+1 dimensions at finite temperature in the
vicinity of critical point. For various lattice sizes in time direction
() we extract high precision values of the inverse critical
coupling and critical values of the 4-th order cumulant of Polyakov loops
(Binder cumulant). We check the universality class of the theory by comparing
the cumulant values to that of the 3D Ising model and find very good agreement.
The Polyakov loop correlators for the indicated lattices are also measured
and the string tension values extracted. The high precision values of critical
coupling and string tension allow us to study the scaling of dimensionless
ratio. The violation of scaling by <10% is observed as the
coupling is varied from weak to strong coupling regime.Comment: 17 pages, 9 figures, minor correction
Non-perturbative renormalization of lattice operators in coordinate space
We present the first numerical implementation of a non-perturbative
renormalization method for lattice operators, based on the study of correlation
functions in coordinate space at short Euclidean distance. The method is
applied to compute the renormalization constants of bilinear quark operators
for the non-perturbative O(a)-improved Wilson action in the quenched
approximation. The matching with perturbative schemes, such as MS-bar, is
computed at the next-to-leading order in continuum perturbation theory. A
feasibility study of this technique with Neuberger fermions is also presented.Comment: 11 pages and 9 figures, LaTeX2
An Investigation of the Soft Pion Relation in Quenched Lattice QCD
A lattice determination of the form factor and decay constants for the
semileptonic decay of heavy pseudoscalar (PS) mesons at zero recoil is
presented from which the soft pion relation is satisfied. Chiral extrapolation
of the form factor is performed at constant . Pole dominance is used to
extrapolate the form factor in heavy quark mass. At the B mass, the form factor
at zero recoil lies somewhat below the ratio of decay constants; the relation
remains satisfied within error.Comment: 3 pages, 2 figure
Methodological tests of the use of trace elements as tracers to assess root activity
peer-reviewedN.J.H. was funded by the Irish Research Council, co-funded by Marie Curie Actions under FP7. The field experiments A, B and G were supported by the European Community's Seventh Framework Programme (FP7/2007-2013) under the grant agreements FP7-266018 (AnimalChange) and FP7- 244983 (MultiSward). Experiment F was supported by the German Science Foundation (FOR 456).Background and aims
There is increasing interest in how resource utilisation in grassland ecosystems is affected by changes in plant diversity and abiotic conditions. Research to date has mainly focussed on aboveground responses and there is limited insight into belowground processes. The aim of this study was to test a number of assumptions for the valid use of the trace elements caesium, lithium, rubidium and strontium as tracers to assess the root activity of several grassland species.
Methods
We carried out a series of experiments addressing the reliability of soil labelling, injection density, incubation time, application rate and the comparability of different tracers in a multiple tracer method.
Results
The results indicate that it is possible to achieve a reliable labelling of soil depths. Tracer injection density affected the variability but not the mean level of plant tracer concentrations. Tracer application rates should be based on pilot studies, because of site- and species-specific responses. The trace elements did not meet prerequisites to be used in a multiple tracer method.
Conclusions
The use of trace elements as tracers is potentially a very useful tool to give insight into plant root activity at different soil depths. This work highlights some of the main benefits and pitfalls of the method and provides specific recommendations to assist the design of tracer experiments and interpretation of the results.N.J.H. was funded by the Irish Research Council, co-funded by Marie Curie Actions under FP7. The field experiments A, B and G were supported by the European Community's Seventh Framework Programme (FP7/2007-2013) under the grant agreements FP7-266018 (AnimalChange) and FP7- 244983 (MultiSward). Experiment F was supported by the German Science Foundation (FOR 456).European Unio
An extended multiscale principle of virtual velocities approach for evolving microstructure
AbstractA hierarchical multiscale approach is presented for modeling microstructure evolution in heterogeneous materials. Preservation of momentum across each scale transition is incorporated through the application of the principle of virtual velocities at the fine scale giving rise to the appropriate continuum momentum balance equations at the coarse scale. In addition to satisfying momentum balance and invariance of momentum among scales, invariance of elastic free energy, stored free energy, and dissipation between two scales of observation is regarded as crucial to the physics of each scale transition. The preservation of this energy partitioning scheme is obtained through construction of constitutive relations within the framework of internal state variable theory. Internal state variables that are directly computed from the fine scale response are introduced to augment the state equations and describe the inelastic energy storage and dissipation within the fine scale. By virtue of a second gradient kinematic decomposition, the framework naturally gives rise to couple stresses
Indications on the Higgs boson mass from lattice simulations
The `triviality' of has been traditionally interpreted within
perturbation theory where the prediction for the Higgs boson mass depends on
the magnitude of the ultraviolet cutoff . This approach crucially
assumes that the vacuum field and its quantum fluctuations rescale in the same
way. The results of the present lattice simulation, confirming previous
numerical indications, show that this assumption is not true. As a consequence,
large values of the Higgs mass can coexist with the limit . As an example, by extrapolating to the Standard Model our results
obtained in the Ising limit of the one-component theory, one can obtain a value
as large as GeV, independently of .Comment: 3 pages, 2 figures, Lattice2003(higgs
Hybrid meson decay from the lattice
We discuss the allowed decays of a hybrid meson in the heavy quark limit. We
deduce that an important decay will be into a heavy quark non-hybrid state and
a light quark meson, in other words, the de-excitation of an excited gluonic
string by emission of a light quark-antiquark pair.
We discuss the study of hadronic decays from the lattice in the heavy quark
limit and apply this approach to explore the transitions from a spin-exotic
hybrid to and where is a scalar meson. We obtain a
signal for the transition emitting a scalar meson and we discuss the
phenomenological implications.Comment: 18 pages, LATEX, 3 ps figure
Topological susceptibility in the SU(3) gauge theory
We compute the topological susceptibility for the SU(3) Yang--Mills theory by
employing the expression of the topological charge density operator suggested
by Neuberger's fermions. In the continuum limit we find r_0^4 chi = 0.059(3),
which corresponds to chi=(191 +/- 5 MeV)^4 if F_K is used to set the scale. Our
result supports the Witten--Veneziano explanation for the large mass of the
eta'.Comment: Final version to appear on Phys. Rev. Let
GABAA Receptor Trafficking-Mediated Plasticity of Inhibitory Synapses
Proper developmental, neural cell-type-specific, and activity-dependent regulation of GABAergic transmission is essential for virtually all aspects of CNS function. The number of GABAA receptors in the postsynaptic membrane directly controls the efficacy of GABAergic synaptic transmission. Thus, regulated trafficking of GABAA receptors is essential for understanding brain function in both health and disease. Here we summarize recent progress in the understanding of mechanisms that allow dynamic adaptation of cell surface expression and postsynaptic accumulation and function of GABAA receptors. This includes activity-dependent and cell-type-specific changes in subunit gene expression, assembly of subunits into receptors, as well as exocytosis, endocytic recycling, diffusion dynamics, and degradation of GABAA receptors. In particular, we focus on the roles of receptor-interacting proteins, scaffold proteins, synaptic adhesion proteins, and enzymes that regulate the trafficking and function of receptors and associated proteins. In addition, we review neuropeptide signaling pathways that affect neural excitability through changes in GABAAR trafficking
A First Principles Estimate of Finite Size Effects in Quark-Gluon Plasma Formation
Using lattice simulations of quenched QCD we estimate the finite size effects
present when a gluon plasma equilibrates in a slab geometry, i.e., finite width
but large transverse dimensions. Significant differences are observed in the
free energy density for the slab when compared with bulk behavior. A small
shift in the critical temperature is also seen. The free energy required to
liberate heavy quarks relative to bulk is measured using Polyakov loops; the
additional free energy required is on the order of 30-40 MeV at 2-3 T_c.Comment: 10 pages, 5 figures, RevTeX; revised version includes comparison with
the Bjorken model and various small improvement
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