5,285 research outputs found
Recent Results of Multimagnetical Simulations of the Ising Model
To investigate order-order interfaces, we perform multimagnetical Monte Carlo
simulations of the and Ising model. Stringent tests of the numerical
methods are performed by reproducing with high precision exact results. In
the physically more interesting case we estimate the amplitude of
the critical interfacial tension.Comment: talk presented at the workshop "Dynamics of First Order Phase
Transitions", Juelich June 1-3; FSU-SCRI-92C-87 preprint; 7 pages; sorry no
figures; needs vanilla.st
A non-perturbative estimate of the heavy quark momentum diffusion coefficient
We estimate the momentum diffusion coefficient of a heavy quark within a pure
SU(3) plasma at a temperature of about 1.5Tc. Large-scale Monte Carlo
simulations on a series of lattices extending up to 192^3*48 permit us to carry
out a continuum extrapolation of the so-called colour-electric imaginary-time
correlator. The extrapolated correlator is analyzed with the help of
theoretically motivated models for the corresponding spectral function.
Evidence for a non-zero transport coefficient is found and, incorporating
systematic uncertainties reflecting model assumptions, we obtain kappa = (1.8 -
3.4)T^3. This implies that the "drag coefficient", characterizing the time
scale at which heavy quarks adjust to hydrodynamic flow, is (1.8 - 3.4)
(Tc/T)^2 (M/1.5GeV) fm/c, where M is the heavy quark kinetic mass. The results
apply to bottom and, with somewhat larger systematic uncertainties, to charm
quarks.Comment: 18 pages. v2: clarifications adde
The inverted XY universality of the superconductivity phase transition
It has been conjectured that the phase transition in the Ginzburg-Landau
theory is dual to the XY model transition. We study numerically a particular
limit of the GL theory where this duality becomes exact, clarifying some of the
problems encountered in standard GL theory simulations. This may also explain
the failure of the superconductor experiments to observe the XY model scaling.Comment: Lattice2002(higgssusy), 3 page
O(2) symmetry breaking vs. vortex loop percolation
We study with lattice Monte Carlo simulations the relation of global O(2)
symmetry breaking in three dimensions to the properties of a geometrically
defined vortex loop network. We find that different definitions of constructing
a network lead to different results even in the thermodynamic limit, and that
with typical definitions the percolation transition does not coincide with the
thermodynamic phase transition. These results show that geometrically defined
percolation observables need not display universal properties related to the
critical behaviour of the system, and do not in general survive in the field
theory limit.Comment: 14 pages; references added, version to appear in Phys.Lett.
Critical point and scale setting in SU(3) plasma: An update
We explore a method developed in statistical physics which has been argued to
have exponentially small finite-volume effects, in order to determine the
critical temperature Tc of pure SU(3) gauge theory close to the continuum
limit. The method allows us to estimate the critical coupling betac of the
Wilson action for temporal extents up to Nt ~ 20 with < 0.1% uncertainties.
Making use of the scale setting parameters r0 and sqrt{t0} in the same range of
beta-values, these results lead to the independent continuum extrapolations Tc
r0 = 0.7457(45) and Tc sqrt{t0} = 0.2489(14), with the latter originating from
a more convincing fit. Inserting a conversion of r0 from literature
(unfortunately with much larger errors) yields Tc / LambdaMSbar = 1.24(10).Comment: 12 pages. v2: clarifications and references added, published versio
The hepta-β-glucoside elicitor-binding proteins from legumes represent a putative receptor family
The ability of legumes to recognize and respond to β-glucan elicitors by synthesizing phytoalexins is consistent with the existence of a membrane-bound β-glucan-binding site. Related proteins of approximately 75 kDa and the corresponding mRNAs were detected in various species of legumes which respond to beta-glucans. The cDNAs for the beta-glucan-binding proteins of bean and soybean were cloned. The deduced 75-kDa proteins are predominantly hydrophilic and constitute a unique class of glucan-binding proteins with no currently recognizable functional domains. Heterologous expression of the soybean beta-glucan-binding protein in tomato cells resulted in the generation of a high-affinity binding site for the elicitor-active hepta-β-glucoside conjugate (K-d = 4.5 nM). Ligand competition experiments with the recombinant binding sites demonstrated similar ligand specificities when compared with soybean. In both soybean and transgenic tomato, membrane-bound, active forms of the glucan-binding proteins coexist with immunologically detectable, soluble but inactive forms of the proteins. Reconstitution of a soluble protein fraction into lipid vesicles regained beta-glucoside-binding activity but with lower affinity (K-d = 130 nM). We conclude that the beta-glucan elicitor receptors of legumes are composed of the 75 kDa glucan-binding proteins as the critical components for ligand-recognition, and of an as yet unknown membrane anchor constituting the plasma membrane-associated receptor complex
Correlation between the reliability of HEMT devices and that of a combined oscillator-amplifier
We evaluate an oscillator-amplifier MMIC submitted to high-temperature operating life time tests. To relate adequately these results with individual components’ results, it is important to realise that failure mechanisms in non-linear MMICs are governed by the maximally instantaneous voltages/currents and hence that comparisons should be conducted at equal instantaneous conditions
Towards the continuum limit in transport coefficient computations
The analytic continuation needed for the extraction of transport coefficients
necessitates in principle a continuous function of the Euclidean time variable.
We report on progress towards achieving the continuum limit for 2-point
correlator measurements in thermal SU(3) gauge theory, with specific attention
paid to scale setting. In particular, we improve upon the determination of the
critical lattice coupling and the critical temperature of pure SU(3) gauge
theory, estimating r0*Tc ~ 0.7470(7) after a continuum extrapolation. As an
application the determination of the heavy quark momentum diffusion coefficient
from a correlator of colour-electric fields attached to a Polyakov loop is
discussed.Comment: 7 pages. To appear in the Proceedings of the 31st International
Symposium on Lattice Field Theory, July 29 - August 3, 2013, Mainz, German
Phase structure and chiral limit of compact lattice QED with Wilson fermions
We study the phase structure and chiral limit of compact lattice QED
with Wilson fermions (both dynamical and quenched). We use the standard Wilson
action (WA) and also the modified action (MA) with some lattice artifacts
suppressed. We show that lattice artifacts influence the distributions of
eigenvalues of the fermionic matrix especially for small values
of . Our main conclusion is that the chiral limit of compact QED
can be efficiently located using different techniques. Sorry, figures are not
included and can be sent by ordinary mail or Fax.Comment: TALK GIVEN AT THE LATTICE '93 INTERNATIONAL SYMPOSIUM LATTICE FIELD
THEORY, DALLAS, USA, OCTOBER 12--16, 1993 3 page
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