1,014 research outputs found
Report of optical ground truth measurements for 5 August 1973, test site number 548532, in support of the Skylab multispectral scanner
There are no author-identified significant results in this report
On the Connection Between Momentum Cutoff and Operator Cutoff Regularizations
Operator cutoff regularization based on the original Schwinger's proper-time
formalism is examined. By constructing a regulating smearing function for the
proper-time integration, we show how this regularization scheme simulates the
usual momentum cutoff prescription yet preserves gauge symmetry even in the
presence of the cutoff scales. Similarity between the operator cutoff
regularization and the method of higher (covariant) derivatives is also
observed. The invariant nature of the operator cutoff regularization makes it a
promising tool for exploring the renormalization group flow of gauge theories
in the spirit of Wilson-Kadanoff blocking transformation.Comment: 28 pages in plain TeX, no figures. revised and expande
Renormalization Group Flow Equations and the Phase Transition in O(N)-models
We derive and solve flow equations for a general O(N)-symmetric effective
potential including wavefunction renormalization corrections combined with a
heat-kernel regularization. We investigate the model at finite temperature and
study the nature of the phase transition in detail. Beta functions, fixed
points and critical exponents \beta, \nu, \delta and \eta for various N are
independently calculated which allow for a verification of universal scaling
relations.Comment: 34 pages, 3 tables, 11 postscript figures, LaTe
Gluon Condensation in Nonperturbative Flow Equations
We employ nonperturbative flow equations for an investigation of the
effective action in Yang-Mills theories. We compute the effective action
for constant color magnetic fields and examine Savvidy's
conjecture of an unstable perturbative vacuum. Our results indicate that the
absolute minimum of occurs for B=0. Gluon condensation is described
by a nonvanishing expectation value of the regularized composite operator
which agrees with phenomenological estimates.Comment: 64 pages, late
Male water striders attract predators to intimidate females into copulation
Despite recent advances in our understanding of sexual conflict and antagonistic coevolution between sexes, the role of interspecific interactions, such as predation, in these evolutionary processes remains unclear. In this paper, we present a new male mating strategy whereby a male water strider Gerris gracilicornis intimidates a female by directly attracting predators as long as she does not accept the male's coercive copulation attempt. We argue that this male strategy is a counteradaptation to the evolution of the female morphological shield protecting her genitalia from coercive intromission by water strider males. The G. gracilicornis mating system clearly represents an effect expected from models of the coevolutionary arms race between sexes, whereby one sex causes a decrease in the fitness component of the other sex. Moreover, our study demonstrates a crucial role that interspecific interactions such as predation can have in the antagonistic coevolution between sexes
Inhomogeneous Field Configurations and the Electroweak Phase Transition
We investigate the effects of inhomogeneous scalar field configurations on
the electroweak phase transition. For this purpose we calculate the leading
perturbative correction to the wave function correction term Z(\vph,T), i.e.,
the kinetic term in the effective action, for the electroweak Standard Model at
finite temperature and the top quark self--mass. Our finding for the fermionic
contribution to Z(\vph,T) is infra--red finite and disagrees with other
recent results. In general, neither the order of the phase transition nor the
temperature at which it occurs change, once Z(\vph,T) is included. But a
non--vanishing, positive (negative) Z(\vph,T) enhances (decreases) the
critical droplet surface tension and the strength of the phase transition. We
find that in the range of parameter space, which allows for a first--order
phase transition, the wave function correction term is negative --- indicating
a weaker phase transition --- and especially for small field values so large
that perturbation theory becomes unreliable.Comment: 23 pages of LaTeX + 3 PostScript figures included in uuencoded form,
FERMI-PUB-93/253-
Lorentz and CPT Violating Chern-Simons Term in the Derivative Expansion of QED
We calculate by the method of dimensional regularization and derivative
expansion the one-loop effective action for a Dirac fermion with a
Lorentz-violating and CPT-odd kinetic term in the background of a gauge field.
We show that this term induces a Chern-Simons modification to Maxwell theory.
Some related issues are also discussed.Comment: 6 pages, no figure, RevTex, A revised versio
Quantum Kinks: Solitons at Strong Coupling
We examine solitons in theories with heavy fermions. These ``quantum''
solitons differ dramatically from semi-classical (perturbative) solitons
because fermion loop effects are important when the Yukawa coupling is strong.
We focus on kinks in a --dimensional theory coupled to
fermions; a large- expansion is employed to treat the Yukawa coupling
nonperturbatively. A local expression for the fermion vacuum energy is derived
using the WKB approximation for the Dirac eigenvalues. We find that fermion
loop corrections increase the energy of the kink and (for large ) decrease
its size. For large , the energy of the quantum kink is proportional to ,
and its size scales as , unlike the classical kink; we argue that these
features are generic to quantum solitons in theories with strong Yukawa
couplings. We also discuss the possible instability of fermions to solitons.Comment: 21 pp. + 2 figs., phyzzx, JHU-TIPAC-92001
Response of nucleons to external probes in hedgehog models: II. General formalism
Linear response theory for SU(2) hedgehog soliton models is developed.Comment: 25 pages, DOE/ER/40322-163, U. of MD PP \#92-225, (ReVTeX
Deriving Non-decoupling Effects of Heavy Fields from the Path Integral: a Heavy Higgs Field in an SU(2) Gauge Theory
We describe a method to remove non-decoupling heavy fields from a quantized
field theory and to construct a low-energy one-loop effective Lagrangian by
integrating out the heavy degrees of freedom in the path integral. We apply
this method to the Higgs boson in a spontaneously broken SU(2) gauge theory
(gauged linear sigma-model). In this context, the background-field method is
generalized to the non-linear representation of the Higgs sector by applying (a
generalization of) the Stueckelberg formalism. The (background) gauge-invariant
renormalization is discussed. At one loop the log M_H-terms of the heavy-Higgs
limit of this model coincide with the UV-divergent terms of the corresponding
gauged non-linear sigma-model, but vertex functions differ in addition by
finite (constant) terms in both models. These terms are also derived by our
method. Diagrammatic calculations of some vertex functions are presented as
consistency check.Comment: 33 Pages LaTeX, 6 figures uuencoded postscrip
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