9,121 research outputs found
Variational Approach to Yang--Mills Theory with non-Gaussian Wave Functionals
A general method for treating non-Gaussian wave functionals in quantum field
theory is presented and applied to the Hamiltonian approach to Yang-Mills
theory in Coulomb gauge in order to include a three-gluon kernel in the
exponential of the vacuum wave functional. The three-gluon vertex is calculated
using the propagators found in the variational approach with a Gaussian trial
wave functional as input.Comment: 3 pages, 4 figures, talk presented at "Quark Confinement and the
Hadron Spectrum IX", Madrid, August 30-September 3, 2010, to appear in the
proceeding
Dynamical Phase Transitions for Fluxes of Mass on Finite Graphs
We study the time-averaged flux in a model of particles that randomly hop on
a finite directed graph. In the limit as the number of particles and the time
window go to infinity but the graph remains finite, the large-deviation rate
functional of the average flux is given by a variational formulation involving
paths of the density and flux. We give sufficient conditions under which the
large deviations of a given time averaged flux is determined by paths that are
constant in time. We then consider a class of models on a discrete ring for
which it is possible to show that a better strategy is obtained producing a
time-dependent path. This phenomenon, called a dynamical phase transition, is
known to occur for some particle systems in the hydrodynamic scaling limit,
which is thus extended to the setting of a finite graph
Non-Gaussian wave functionals in Coulomb gauge Yang--Mills theory
A general method to treat non-Gaussian vacuum wave functionals in the
Hamiltonian formulation of a quantum field theory is presented. By means of
Dyson--Schwinger techniques, the static Green functions are expressed in terms
of the kernels arising in the Taylor expansion of the exponent of the vacuum
wave functional. These kernels are then determined by minimizing the vacuum
expectation value of the Hamiltonian. The method is applied to Yang--Mills
theory in Coulomb gauge, using a vacuum wave functional whose exponent contains
up to quartic terms in the gauge field. An estimate of the cubic and quartic
interaction kernels is given using as input the gluon and ghost propagators
found with a Gaussian wave functional.Comment: 27 pages, 21 figure
The deconfinement phase transition in the Hamiltonian approach to Yang--Mills theory in Coulomb gauge
The deconfinement phase transition of SU(2) Yang--Mills theory is
investigated in the Hamiltonian approach in Coulomb gauge assuming a
quasi-particle picture for the grand canonical gluon ensemble. The thermal
equilibrium state is found by minimizing the free energy with respect to the
quasi-gluon energy. Above the deconfinement phase transition the ghost form
factor remains infrared divergent but its infrared exponent is approximately
halved, while the gluon energy, being infrared divergent in the confined phase,
becomes infrared finite in the deconfined phase. For the effective gluon mass
we find a critical exponent of 0.37. Using the lattice results for the gluon
propagator to fix the scale, the deconfinement transition temperature is
obtained in the range of 275 to 290 MeV.Comment: 20 pages, 13 figures, accepted for publication by Phys. Rev.
Autonomous propulsion of carbon nanotubes powered by a multienzyme ensemble
Covalent attachment of the enzymes glucose oxidase and catalase to carbon nanotubes enables the tandem catalytic conversion of glucose and H2O2 formed to power autonomous movement of the nanotubes.
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