405 research outputs found
Two- and three-point Green's functions in two-dimensional Landau-gauge Yang-Mills theory
The ghost and gluon propagator and the ghost-gluon and three-gluon vertex of
two-dimensional SU(2) Yang-Mills theory in (minimal) Landau gauge are studied
using lattice gauge theory. It is found that the results are qualitatively
similar to the ones in three and four dimensions. The propagators and the
Faddeev-Popov operator behave as expected from the Gribov-Zwanziger scenario.
In addition, finite volume effects affecting these Green's functions are
investigated systematically. The critical infrared exponents of the
propagators, as proposed in calculations using stochastic quantization and
Dyson-Schwinger equations, are confirmed quantitatively. For this purpose
lattices of volume up to (42.7 fm)^2 have been used.Comment: 14 pages, 14 figures, 4 tables, references adde
Decoupling of the longitudinal polarization of the vector field in the massless Higgs-Kibble model
It is shown that the three dimensionally longitudinal component of the vector
field decouples in the massless limit of nonabelian Higgs model.Comment: 6 pages, no figure
Exploratory study of three-point Green's functions in Landau-gauge Yang-Mills theory
Green's functions are a central element in the attempt to understand
non-perturbative phenomena in Yang-Mills theory. Besides the propagators,
3-point Green's functions play a significant role, since they permit access to
the running coupling constant and are an important input in functional methods.
Here we present numerical results for the two non-vanishing 3-point Green's
functions in 3d pure SU(2) Yang-Mills theory in (minimal) Landau gauge, i.e.
the three-gluon vertex and the ghost-gluon vertex, considering various
kinematical regimes. In this exploratory investigation the lattice volumes are
limited to 20^3 and 30^3 at beta=4.2 and beta=6.0. We also present results for
the gluon and the ghost propagators, as well as for the eigenvalue spectrum of
the Faddeev-Popov operator. Finally, we compare two different numerical methods
for the evaluation of the inverse of the Faddeev-Popov matrix, the point-source
and the plane-wave-source methods.Comment: 18 pages, 12 figures, 3 table
Covariant gauges at finite temperature
A prescription is presented for real-time finite-temperature perturbation
theory in covariant gauges, in which only the two physical degrees of freedom
of the gauge-field propagator acquire thermal parts. The propagators for the
unphysical degrees of freedom of the gauge field, and for the Faddeev-Popov
ghost field, are independent of temperature. This prescription is applied to
the calculation of the one-loop gluon self-energy and the two-loop interaction
pressure, and is found to be simpler to use than the conventional one.Comment: 11 pages plus pictex figures (the leading-temperature contributions
given in sect 3.1 were incomplete) CERN-TH-6491/92, published in Nucl Phys
B383 (1992) 60
Spectral properties of the Landau gauge Faddeev-Popov operator in lattice gluodynamics
Recently we reported on the infrared behavior of the Landau gauge gluon and
ghost dressing functions in SU(3) Wilson lattice gluodynamics with special
emphasis on the Gribov problem. Here we add an investigation of the spectral
properties of the Faddeev-Popov operator at =5.8 and 6.2 for lattice
sizes 12^4, 16^4 and 24^4. The larger the volume the more of its eigenvalues
are found accumulated close to zero. Using the eigenmodes for the spectral
representation it turns out that for our smallest lattice O(200) eigenmodes are
sufficient to saturate the ghost propagator at lowest momentum. We associate
exceptionally large values of the ghost propagator to extraordinary
contributions of low-lying eigenmodes.Comment: 7 pages, 8 figure
Superfield description of 5D supergravity on general warped geometry
We provide a systematic and practical method of deriving 5D supergravity
action described by 4D superfields on a general warped geometry, including a
non-BPS background. Our method is based on the superconformal formulation of 5D
supergravity, but is easy to handle thanks to the superfield formalism. We
identify the radion superfield in the language of 5D superconformal gravity,
and clarify its appearance in the action. We also discuss SUSY breaking effects
induced by a deformed geometry due to the backreaction of the radius
stabilizer.Comment: 25 pages, no figures, LaTeX, final version to appear in JHE
Towards the infrared limit in SU(3) Landau gauge lattice gluodynamics
We study the behavior of the gluon and ghost dressing functions in SU(3)
Landau gauge at low momenta available on lattice sizes 12^4-32^4 at
=5.8, 6.0 and 6.2. We demonstrate the ghost dressing function to be
systematically dependent on the choice of Gribov copies, while the influence on
the gluon dressing function is not resolvable. The running coupling given in
terms of these functions is found to be decreasing for momenta q<0.6 GeV. We
study also effects of the finite volume and of the lattice discretization.Comment: 10 pages, 6 figures. Revised version to appear in Phys.Rev.D. Title
modified; a new subsection discusses finite volume and finite lattice spacing
effects; few references adde
A Comment on the Cosmological Constant Problem in Spontaneously Broken Supergravity
In spontaneously broken supergravity with non-flat potential the vanishing of
the cosmological constant is usually associated with a non-trivial balancing of
two opposite-sign contributions. We make the simple observation that, in an
appropriately defined expansion of the superfield action in inverse powers of
, this tuning corresponds to the absence of two specific operators. It is
then tempting to speculate what kind of non-standard symmetry or structural
principle might underlie the observed extreme smallness of the corresponding
coefficients in the real world. Independently of such speculations, the
suggested expansion appears to be a particularly simple and convenient starting
point for the effective field theory analysis of spontaneously broken
supergravity models.Comment: 6 pages LaTe
SUSY breaking mediation by throat fields
We investigate, in the general framework of KKLT, the mediation of
supersymmetry breaking by fields propagating in the strongly warped region of
the compactification manifold ('throat fields'). Such fields can couple both to
the supersymmetry breaking sector at the IR end of the throat and to the
visible sector at the UV end. We model the supersymmetry breaking sector by a
chiral superfield which develops an F-term vacuum expectation value. It turns
out that the mediation effect of vector multiplets propagating in the throat
can compete with modulus-anomaly mediation. Moreover, such vector fields are
naturally present as the gauge fields arising from isometries of the throat
(most notably the SO(4) isometry of the Klebanov-Strassler solution). Their
mediation effect is important in spite of their large 4d mass. The latter is
due to the breaking of the throat isometry by the compact manifold at the UV
end of the throat. The contribution from heavy chiral superfields is found to
be subdominant.Comment: 15 pages; v2: typos corrected, references added; v3: comments adde
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