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 ${\lambda} (\bar{\Psi} {\Psi})^2$, 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 $(3+1)$ space-time. This is particularly apparent when we represent the results with diagrams in the extended $(4+1)$ manifold, since they usually encompass more diagrams in Galilean $(3+1)$ 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

Large Beyond-Leading-Order Effects in b -> s gamma in Supersymmetry with General Flavor Mixing

We examine squark--gluino loop effects on the process $b \to s \gamma$ 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 $\tan\beta$ and $\mu>0$. 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 $BR(B \to X_s \gamma)$. 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 $\mu<0$ can also become allowed for $M_{SUSY}$ as small as $\sim$ 200 GeV, compared to > $\sim$ 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 $K^{(0)}_{cb}$ 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