40,793 research outputs found
Prototype Graphs for radiative Corrections to Polarized Chargino or Neutralino Production in Electron-Positron Annihilation
We present the contributions from all types of one-loop corrections to the
scattering amplitude for the pair production of polarized charginos or
neutralinos from polarized electron-positron annihilation. The contributions
are classified in terms of ``prototypes'' distinguished by the number of
particles inside the loops and their spins. The results are quoted in terms of
the Veltman-Passarino functions in terms of general couplings and internal
masses. The results can therefore be applied to any supersymmetric extension of
the Standard Model or indeed to any polarized fermion pair production process
in electron-positron annihilation.Comment: LATEX 38 pages, 26 figure
The initial conditions of the Universe and holography
We address the initial conditions for an expanding cosmology using the
holographic principle. For the case of a closed model, the old prescription of
Fishler and Susskind, that uses the particle horizon to encode the bulk degrees
of freedom, can be implemented for accelerated models with enough acceleration.
As a bonus we have singularity free bouncing models. The bound is saturated for
co-dimension one branes dominated universes.Comment: Talk presented at the XXVIII Spanish Relativity Meeting E.R.E. 2005,
Oviedo, September 6-10, 2005, to be published by AIP Conference Proceedings,
4 page
Constraining Bilinear R-Parity Violation from Neutrino Masses
We confront the R-parity violating MSSM model with the neutrino oscillation
data. Investigating the 1-loop particle-sparticle diagrams with additional
bilinear insertions on the external neutrino lines we construct the relevant
contributions to the neutrino mass matrix. A comparison of the so-obtained
matrices with the experimental ones assuming normal or inverted hierarchy and
taking into account possible CP violating phases, allows to set constraints on
the values of the bilinear coupling constants. A similar calculation is
presented with the input from the Heidelberg-Moscow neutrinoless double beta
decay experiment. We base our analysis on the renormalization group evolution
of the MSSM parameters which are unified at the GUT scale. Using the obtained
bounds we calculate the contributions to the Majorana neutrino transition
magnetic moments.Comment: I've decided to move the collection of my papers to arXiv for easier
acces
Rayleigh-Taylor instability in partially ionized compressible plasmas: one fluid approach
We study the modification of the classical criterion for the linear onset and
growth rate of the Rayleigh-Taylor instability (RTI) in a partially ionized
(PI) plasma in the one-fluid description, considering a generalized induction
equation. The governing linear equations and appropriate boundary conditions,
including gravitational terms, are derived and applied to the case of the RTI
in a single interface between two partially ionized plasmas. The boundary
conditions lead to an equation for the frequencies in which some of them have
positive complex parts, marking the appearance of the RTI. We study the
ambipolar term alone first, extending the result to the full induction equation
later. We find that the configuration is always unstable because of the
presence of a neutral species. In the classical stability regime the growth
rate is small, since the collisions prevent the neutral fluid to fully develop
the RTI. For parameters in the classical instability regime the growth rate is
lowered, but for the considered theoretical values of the collision frequencies
and diffusion coefficients for solar prominences the differences with the
compressible MHD case are small. We conclude that PI modifies some aspects of
the linear RTI instability, since it takes into account that neutrals do not
feel the stabilizing effect of the magnetic field. For the set of parameters
representative for solar prominences, our model gives the resulting timescale
comparable with observed lifetimes of RTI plumes.Comment: Accepted for publication in Astronomy & Astrophysic
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