705 research outputs found
On Bogovski\u{\i} and regularized Poincar\'e integral operators for de Rham complexes on Lipschitz domains
We study integral operators related to a regularized version of the classical
Poincar\'e path integral and the adjoint class generalizing Bogovski\u{\i}'s
integral operator, acting on differential forms in . We prove that these
operators are pseudodifferential operators of order -1. The Poincar\'e-type
operators map polynomials to polynomials and can have applications in finite
element analysis. For a domain starlike with respect to a ball, the special
support properties of the operators imply regularity for the de Rham complex
without boundary conditions (using Poincar\'e-type operators) and with full
Dirichlet boundary conditions (using Bogovski\u{\i}-type operators). For
bounded Lipschitz domains, the same regularity results hold, and in addition we
show that the cohomology spaces can always be represented by
functions.Comment: 23 page
Perturbative and Nonperturbative Kolmogorov Turbulence in a Gluon Plasma
In numerical simulations of nonabelian plasma instabilities in the hard-loop
approximation, a turbulent spectrum has been observed that is characterized by
a phase-space density of particles with exponent , which is larger than expected from relativistic
scatterings. Using the approach of Zakharov, L'vov and Falkovich, we analyse
possible Kolmogorov coefficients for relativistic -particle
processes, which give at most perturbatively for an energy cascade.
We discuss nonperturbative scenarios which lead to larger values. As an extreme
limit we find the result generically in an inherently nonperturbative
effective field theory situation, which coincides with results obtained by
Berges et al.\ in large- scalar field theory. If we instead assume that
scaling behavior is determined by Schwinger-Dyson resummations such that the
different scaling of bare and dressed vertices matters, we find that
intermediate values are possible. We present one simple scenario which would
single out .Comment: published versio
Ward identity and electrical conductivity in hot QED
We study the Ward identity for the effective photon-electron vertex summing
the ladder diagrams contributing to the electrical conductivity in hot QED at
leading logarithmic order. It is shown that the Ward identity requires the
inclusion of a new diagram in the integral equation for the vertex that has not
been considered before. The real part of this diagram is subleading and
therefore the final expressions for the electrical conductivity at leading
logarithmic order are not affected.Comment: 25 pages with 5 eps figures, discussion in section 3 improved; to
appear in JHE
Shear viscosity of hot scalar field theory in the real-time formalism
Within the closed time path formalism a general nonperturbative expression is
derived which resums through the Bethe-Salpter equation all leading order
contributions to the shear viscosity in hot scalar field theory. Using a
previously derived generalized fluctuation-dissipation theorem for nonlinear
response functions in the real-time formalism, it is shown that the
Bethe-Salpeter equation decouples in the so-called (r,a) basis. The general
result is applied to scalar field theory with pure lambda*phi**4 and mixed
g*phi**3+lambda*phi**4 interactions. In both cases our calculation confirms the
leading order expression for the shear viscosity previously obtained in the
imaginary time formalism.Comment: Expanded introduction and conclusions. Several references and a
footnote added. Fig.5 and its discussion in the text modified to avoid double
counting. Signs in Eqs. (45) and (53) correcte
Finite Temperature Effective Potential for the Abelian Higgs Model to the Order
A complete calculation of the finite temperature effective potential for the
abelian Higgs model to the order is presented and the result is
expressed in terms of physical parameters defined at zero temperature. The
absence of a linear term is verified explicitly to the given order and proven
to survive to all orders. The first order phase transition has weakened in
comparison with lower order calculation, which shows up in a considerable
decrease of the surface tension. The only difference from the original version
is the splitting of some overlong lines causing problems with certain mailers.Comment: 13 pages LaTex ( figures not included , hardcopy available on request
: [email protected] or t00heb@dhhdesy3 ) , DESY 93-08
A Gauge field Induced by the Global Gauge Invariance of Action Integral
As a general rule, it is considered that the global gauge invariance of an
action integral does not cause the occurrence of gauge field. However, in this
paper we demonstrate that when the so-called localized assumption is excluded,
the gauge field will be induced by the global gauge invariance of the action
integral. An example is given to support this conclusion.Comment: 13 pages. Some typing errors are corrected and the format is update
High- Elastic -scattering and QCD predictions
In the framework of pertubative QCD it is argued that in the elastic
-scattering at few the light-cone-frame
helicity-flip amplitudes could not be omitted. The obtained ratio
of Rosenbluth structure functions is shown to be in a good agreement with
experimental data. The high behavior of tensor analysing power
is discussed.Comment: 6 pages + 2 ps figures not included, LaTeX, ITP-93-33
Resummation Methods at Finite Temperature: The Tadpole Way
We examine several resummation methods for computing higher order corrections
to the finite temperature effective potential, in the context of a scalar
theory. We show by explicit calculation to four loops that dressing
the propagator, not the vertex, of the one-loop tadpole correctly counts
``daisy'' and ``super-daisy'' diagrams.Comment: 18 pages, LaTeX, CALT-68-1858, HUTP-93-A011, EFI-93-2
A Diagrammatic Interpretation of the Boltzmann Equation
We study nonlinear response in weakly coupled nonequilibrium theory
in the context of both classical transport theory and real time quantum field
theory, based on a generalized Kubo formula which we derive. A novel connection
between these two approaches is established which provides a diagrammatic
interpretation of the Boltzmann equation.Comment: 5 pages in RevTex with 4 Postscript figure
Electroweak phase diagram at finite lepton number density
We study the thermodynamics of the electroweak theory at a finite lepton
number density. The phase diagram of the theory is calculated by relating the
full 4-dimensional theory to a 3-dimensional effective theory which has been
previously solved using nonperturbative methods. It is seen that the critical
temperature increases and the value of the Higgs boson mass at which the first
order phase transition line ends decreases with increasing leptonic chemical
potential.Comment: 16 pages, 14 figures, RevTex4, v2: references added, minor
corrections, v3: small changes, references added, published in Phys. Rev.
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