455 research outputs found
Large-area thin-film modules
The low cost potential of thin film solar cells can only be fully realized if large area modules can be made economically with good production yields. This paper deals with two of the critical challenges. A scheme is presented which allows the simple, economical realization of the long recognized, preferred module structure of monolithic integration. Another scheme reduces the impact of shorting defects and, as a result, increases the production yields. Analytical results demonstrating the utilization and advantages of such schemes are discussed
GLOBAL STABILIZATION OF SYSTEMS CONTAINING A DOUBLE INTEGRATOR USING A SATURATED LINEAR CONTROLLER
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/57819/1/SatDoubleIntegFengIJRNC1999.pd
ANTI-WINDUP COMPENSATOR SYNTHESIS FOR SYSTEMS WITH SATURATION ACTUATORS
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/57796/1/Anti-WindupCompensatorSynthesisforSystemswithSaturationActuators.pd
An Infrared Safe perturbative approach to Yang-Mills correlators
We investigate the 2-point correlation functions of Yang-Mills theory in the
Landau gauge by means of a massive extension of the Faddeev-Popov action. This
model is based on some phenomenological arguments and constraints on the
ultraviolet behavior of the theory. We show that the running coupling constant
remains finite at all energy scales (no Landau pole) for and argue that
the relevant parameter of perturbation theory is significantly smaller than 1
at all energies. Perturbative results at low orders are therefore expected to
be satisfactory and we indeed find a very good agreement between 1-loop
correlation functions and the lattice simulations, in 3 and 4 dimensions.
Dimension 2 is shown to play the role of an upper critical dimension, which
explains why the lattice predictions are qualitatively different from those in
higher dimensions.Comment: 16 pages, 7 figures, accepted for publication in PR
The Gribov parameter and the dimension two gluon condensate in Euclidean Yang-Mills theories in the Landau gauge
The local composite operator A^2 is added to the Zwanziger action, which
implements the restriction to the Gribov region in Euclidean Yang-Mills
theories in the Landau gauge. We prove the renormalizability of this action to
all orders of perturbation theory. This allows to study the dimension two gluon
condensate by the local composite operator formalism when the restriction
is taken into account. The effective action is evaluated at one-loop order in
the MSbar scheme. We obtain explicit values for the Gribov parameter and for
the mass parameter due to , but the expansion parameter turns out to be
rather large. Furthermore, an optimization of the perturbative expansion in
order to reduce the dependence on the renormalization scheme is performed. The
properties of the vacuum energy, with or without , are investigated. It is
shown that in the original Gribov-Zwanziger formulation (without ), the
vacuum energy is always positive at 1-loop order, independently from the
renormalization scheme and scale. With , we are unable to come to a
definite conclusion at the order considered. In the MSbar scheme, we still find
a positive vacuum energy, again with a relatively large expansion parameter,
but there are renormalization schemes in which the vacuum energy is negative,
albeit the dependence on the scheme itself appears to be strong. We recover the
well known consequences of the restriction, and this in the presence of :
an infrared suppression of the gluon propagator and an enhancement of the ghost
propagator. This behaviour is in qualitative agreement with the results
obtained from the studies of the Schwinger-Dyson equations and from lattice
simulations.Comment: 42 pages, 10 .eps figures. v2: Version accepted for publication in
Phys.Rev.D. Added references. Technical details have been collected in two
appendice
Poisson homology of r-matrix type orbits I: example of computation
In this paper we consider the Poisson algebraic structure associated with a
classical -matrix, i.e. with a solution of the modified classical
Yang--Baxter equation. In Section 1 we recall the concept and basic facts of
the -matrix type Poisson orbits. Then we describe the -matrix Poisson
pencil (i.e the pair of compatible Poisson structures) of rank 1 or -type
orbits of . Here we calculate symplectic leaves and the integrable
foliation associated with the pencil. We also describe the algebra of functions
on -type orbits. In Section 2 we calculate the Poisson homology of
Drinfeld--Sklyanin Poisson brackets which belong to the -matrix Poisson
family
A refinement of the Gribov-Zwanziger approach in the Landau gauge: infrared propagators in harmony with the lattice results
Recent lattice data have reported an infrared suppressed, positivity
violating gluon propagator which is nonvanishing at zero momentum and a ghost
propagator which is no longer enhanced. This paper discusses how to obtain
analytical results which are in qualitative agreement with these lattice data
within the Gribov-Zwanziger framework. This framework allows one to take into
account effects related to the existence of gauge copies, by restricting the
domain of integration in the path integral to the Gribov region. We elaborate
to great extent on a previous short paper by presenting additional results,
also confirmed by the numerical simulations. A detailed discussion on the soft
breaking of the BRST symmetry arising in the Gribov-Zwanziger approach is
provided.Comment: 38 pages, 9 figures, the content of section V has been extended and
adapte
Physical phase space of lattice Yang-Mills theory and the moduli space of flat connections on a Riemann surface
It is shown that the physical phase space of \g-deformed Hamiltonian
lattice Yang-Mills theory, which was recently proposed in refs.[1,2], coincides
as a Poisson manifold with the moduli space of flat connections on a Riemann
surface with handles and therefore with the physical phase space of
the corresponding -dimensional Chern-Simons model, where and are
correspondingly a total number of links and vertices of the lattice. The
deformation parameter \g is identified with and is an
integer entering the Chern-Simons action.Comment: 12 pages, latex, no figure
A study of the gauge invariant, nonlocal mass operator in Yang-Mills theories
The nonlocal mass operator is
considered in Yang-Mills theories in Euclidean space-time. It is shown that the
operator can be cast in local
form through the introduction of a set of additional fields. A local and
polynomial action is thus identified. Its multiplicative renormalizability is
proven by means of the algebraic renormalization in the class of linear
covariant gauges. The anomalous dimensions of the fields and of the mass
operator are computed at one loop order. A few remarks on the possible role of
this operator for the issue of the gauge invariance of the dimension two
condensates are outlined.Comment: 34 page
Hamiltonian structures of fermionic two-dimensional Toda lattice hierarchies
By exhibiting the corresponding Lax pair representations we propose a wide
class of integrable two-dimensional (2D) fermionic Toda lattice (TL)
hierarchies which includes the 2D N=(2|2) and N=(0|2) supersymmetric TL
hierarchies as particular cases. We develop the generalized graded R-matrix
formalism using the generalized graded bracket on the space of graded operators
with involution generalizing the graded commutator in superalgebras, which
allows one to describe these hierarchies in the framework of the Hamiltonian
formalism and construct their first two Hamiltonian structures. The first
Hamiltonian structure is obtained for both bosonic and fermionic Lax operators
while the second Hamiltonian structure is established for bosonic Lax operators
only.Comment: 12 pages, LaTeX, the talks delivered at the International Workshop on
Classical and Quantum Integrable Systems (Dubna, January 24 - 28, 2005) and
International Conference on Theoretical Physics (Moscow, April 11 - 16, 2005
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