3,390 research outputs found
Bound on the string tension by the excitation probability for a vortex
A lower bound on the string tension for large beta in SU(2) LGT is derived.
The derivation is from first principles and bounds the string tension from
below by the expectation for the excitation of a single `tagged' thick vortex
winding around the lattice. Thus confinement follows if this expectation
remains nonvanishing at large beta. Numerical simulations are presented to show
that this is indeed the case.Comment: LATTICE99(confine), 3 pages, 3 epsf figures, LaTeX, espcrc2.st
Absence of confinement in the absence of vortices
We consider the Wilson loop expectation in SU(2) lattice gauge theory in the
presence of constraints. The constraints eliminate from the functional measure
gauge field configurations whose physical interpretation is that of thick
center vortices linking with the loop. We give a simple proof that, for
dimension , the so constrained Wilson loop follows perimeter law,
i.e. non-confining behavior, at weak coupling (low temperature). Thus the
presence of vortex configurations is a necessary condition for confinement.Comment: 14 pages, LaTeX fil
SO(3) vortices and disorder in the 2d SU(2) chiral model
We study the correlation function of the 2d SU(2) principal chiral model on
the lattice. By rewriting the model in terms of Z(2) degrees of freedom coupled
to SO(3) vortices we show that the vortices play a crucial role in disordering
the correlations at low temperature. Using a series of exact transformations we
prove that, if satisfied, certain inequalities between vortex correlations
imply exponential fall-off of the correlation function at arbitrarily low
temperatures. We also present some Monte Carlo evidence that these correlation
inequalities are indeed satisfied. Our method can be easily translated to the
language of 4d SU(2) gauge theory to establish the role of corresponding SO(3)
monopoles in maintaining confinement at small couplings.Comment: 13 pages LaTe
Description of two-electron atoms with correct cusp conditions
New sets of functions with arbitrary large finite cardinality are constructed
for two-electron atoms. Functions from these sets exactly satisfy the Kato's
cusp conditions. The new functions are special linear combinations of
Hylleraas- and/or Kinoshita-type terms. Standard variational calculation,
leading to matrix eigenvalue problem, can be carried out to calculate the
energies of the system. There is no need for optimization with constraints to
satisfy the cusp conditions. In the numerical examples the ground state energy
of the He atom is considered
Pion condensation in the two--flavor chiral quark model at finite baryochemical potential
Pion condensation is studied at one--loop level and nonzero baryochemical
potential in the framework of two flavor constituent quark model using the
one--loop level optimized perturbation theory for the resummation of the
perturbative series. A Landau type of analysis is presented for the
investigation of the phase boundary between the pion condensed/non-condensed
phases. The statement that the condensation starts at \muI = m_{\pi} is
slightly modified by one--loop corrections. The second order critical surface
is determined and analysed in the \muI-\muB-T space. The \muI dependence of
the one--loop level charged pion pole masses is also studied.Comment: 12 pages, 5 figures, submitted to PR
SO(3) vortices as a mechanism for generating a mass gap in the 2d SU(2) principal chiral model
We propose a mechanism that can create a mass gap in the SU(2) chiral spin
model at arbitrarily small temperatures. We give a sufficient condition for the
mass gap to be non-zero in terms of the behaviour of an external Z(2) flux
introduced by twisted boundary conditions. This condition in turn is
transformed into an effective dual Ising model with an external magnetic field
generated by SO(3) vortices. We show that having a nonzero magnetic field in
the effective Ising model is sufficient for the SU(2) system to have a mass
gap. We also show that certain vortex correlation inequalities, if satisfied,
would imply a nonzero effective magnetic field. Finally we give some
plausibility arguments and Monte Carlo evidence for the required correlation
inequalities.Comment: 33 pages, LaTeX2e, all figures included in LaTeX forma
Anderson Localization in Quark-Gluon Plasma
At low temperature the low end of the QCD Dirac spectrum is well described by
chiral random matrix theory. In contrast, at high temperature there is no
similar statistical description of the spectrum. We show that at high
temperature the lowest part of the spectrum consists of a band of statistically
uncorrelated eigenvalues obeying essentially Poisson statistics and the
corresponding eigenvectors are extremely localized. Going up in the spectrum
the spectral density rapidly increases and the eigenvectors become more and
more delocalized. At the same time the spectral statistics gradually crosses
over to the bulk statistics expected from the corresponding random matrix
ensemble. This phenomenon is reminiscent of Anderson localization in disordered
conductors. Our findings are based on staggered Dirac spectra in quenched SU(2)
lattice simulations.Comment: 11 pages, 8 figure
Building valoristaion strategies for biodiverse products - the approach
The market valorisation of ‘diverse food products’ is crucial to increase diversity in farming systems. It involves multiple actors, from the field to the table, and requires an integrated approach to take into account several dimensions involved
Building Valorisation Strategies for Biodiverse Products - Case Studies
The market valorisation of ‘diverse food products’ is crucial to promote agrobiodiversity. Despite the differences due to the specific contexts, valorisation strategies show relevant common features
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