150 research outputs found
Tachyon condensation on brane sphalerons
We consider a sphaleron solution in field theory that provides a toy model
for unstable D-branes of string theory. We investigate the tachyon condensation
on a Dp-brane. The localized modes, including a tachyon, arise in the spectrum
of a sphaleron solution of a \phi^4 field theory on M^{p+1}\times S^1. We use
these modes to find a multiscalar tachyon potential living on the sphaleron
world-volume. A complete cancelation between brane tension and the minimum of
the tachyon potential is found as the size of the circle becomes small.Comment: To appear in JHEP, 13 pages, 2 eps figures, minor changes and
references adde
Path-integral quantization of Galilean Fermi fields
The Galilei-covariant fermionic field theories are quantized by using the
path-integral method and five-dimensional Lorentz-like covariant expressions of
non-relativistic field equations. Firstly, we review the five-dimensional
approach to the Galilean Dirac equation, which leads to the Levy-Leblond
equations, and define the Galilean generating functional and Green's functions
for positive- and negative-energy/mass solutions. Then, as an example of
interactions, we consider the quartic self-interacting potential , and we derive expressions for the 2- and 4-point
Green's functions. Our results are compatible with those found in the
literature on non-relativistic many-body systems. The extended manifold allows
for compact expressions of the contributions in space-time. This is
particularly apparent when we represent the results with diagrams in the
extended manifold, since they usually encompass more diagrams in
Galilean space-time.Comment: LATEX file, 27 pages, 8 figures; typos in the journal version are
removed, equation (1) in Introduction is correcte
Probing neutrino properties with charged scalar lepton decays
Supersymmetry with bilinear R-parity violation provides a predictive
framework for neutrino masses and mixings in agreement with current neutrino
oscillation data. The model leads to striking signals at future colliders
through the R-parity violating decays of the lightest supersymmetric particle.
Here we study charged scalar lepton decays and demonstrate that if the scalar
tau is the LSP (i) it will decay within the detector, despite the smallness of
the neutrino masses, (ii) the relative ratio of branching ratios Br({tilde
tau}_1 --> e sum nu_i)/ Br({tilde tau}_1 --> mu sum nu_i) is predicted from the
measured solar neutrino angle, and (iii) scalar muon and scalar electron decays
will allow to test the consistency of the model. Thus, bilinear R-parity
breaking SUSY will be testable at future colliders also in the case where the
LSP is not the neutralino.Comment: 24 pages, 8 ps figs Report-no.: IFIC/02-33 and ZU-TH 11/0
A general analysis with trilinear and bilinear R-parity violating couplings in the light of recent SNO data
We analyse an extension of the minimal supersymmetric standard model
including the dominant trilinear and bilinear R-parity violating contributions.
We take the trilinear terms from the superpotential and the bilinear terms from
the superpotential as well as the scalar potential. We compute the neutrino
masses induced by those couplings and determine the allowed ranges of the
R-parity violating parameters that are consistent with the latest SNO results,
atmospheric data and the Chooz constraint. We also estimate the effective mass
for neutrinoless double beta decay in such scenarios.Comment: 7 pages, Revtex, 1 PS figur
Fermion Electric Dipole Moments in Supersymmetric Models with R-parity Violation
We analyze the electron and neutron electric dipole moments induced by
R-parity violating interactions in supersymmetric models. It is pointed out
that dominant contributions can come from one-loop diagrams involving both the
bilinear and trilinear R-parity odd couplings, leading to somewhat severe
constraints on the products of those couplings.Comment: Revtex, 19pp, four figures in axodraw.st
Neutrino masses in R-parity violating supersymmetric models
We study neutrino masses and mixing in R-parity violating supersymmetric
models with generic soft supersymmetry breaking terms. Neutrinos acquire masses
from various sources: Tree level neutrino--neutralino mixing and loop effects
proportional to bilinear and/or trilinear R-parity violating parameters. Each
of these contributions is controlled by different parameters and have different
suppression or enhancement factors which we identified. Within an Abelian
horizontal symmetry framework these factors are related and specific
predictions can be made. We found that the main contributions to the neutrino
masses are from the tree level and the bilinear loops and that the observed
neutrino data can be accommodated once mild fine-tuning is allowed.Comment: 18 pages; minor typos corrected. To be published in Physical Review
Efeitos da terra diatomĂĄcea sobre Diabrotica speciosa (Germar, 1824) (Coleoptera: Chrysomelidae) em batata inglesa
Large Beyond-Leading-Order Effects in b -> s gamma in Supersymmetry with General Flavor Mixing
We examine squark--gluino loop effects on the process in
minimal supersymmetry with general flavor mixing in the squark sector. In the
regime of heavy squarks and gluino, we derive analytic expressions for the
beyond--LO corrections to the Wilson coefficients and find them to be often
large, especially at large and . The ensuing ranges of
values of the Wilson coefficients are typically smaller than in the LO
approximation, and sometimes even change sign. This has the effect of often
reducing, relative to the LO, the magnitude of supersymmetric contributions to
. This ``focusing effect'' is caused by contributions
from: (i) an RG evolution of the Wilson coefficients; (ii) a correction to the
LO chargino contribution to the Wilson coefficients, which can considerably
reduce the LO gluino contribution. This partial cancellation of the two
contributions takes place only in the case of general flavor mixing. As a
result, stringent lower bounds on the mass scale of superpartners, which apply
in the case of minimal flavor violation, can be substantially reduced for even
small departures from the scenario. The often disfavored case of can
also become allowed for as small as 200 GeV, compared to >
500 GeV at LO and over 2 TeV in the case of minimal flavor violation.
Limits on the allowed amount of flavor mixing among the 2nd and 3rd generation
down--type squarks are also typically considerably weakened. The input CKM
matrix element can be larger than the experimental value by a
factor of ten, or can be as small as zero.Comment: 46 page, 36 figures. v2: some clarifications and Ref.[5] added.
Version to appear in JHE
The Earth: Plasma Sources, Losses, and Transport Processes
This paper reviews the state of knowledge concerning the source of magnetospheric plasma at Earth. Source of plasma, its acceleration and transport throughout the system, its consequences on system dynamics, and its loss are all discussed. Both observational and modeling advances since the last time this subject was covered in detail (Hultqvist et al., Magnetospheric Plasma Sources and Losses, 1999) are addressed
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