122 research outputs found
Distortion of the acoustic peaks in the CMBR due to a primordial magnetic field
In this paper we study the effect of a magnetic field on the fluctuation
spectrum of the cosmic microwave background. We find that upcoming measurements
might give interesting bounds on large scale magnetic fields in the early
Universe. If the effects are seen, it might be possible to establish the
presence of different fields in different patches of the sky. Absence of any
effect, will provide by one order of magnitude a better limit for a primordial
field, now given by nucleosynthesis.Comment: 10 pages, 2 .ps figures included, extra reference added and
typographical errors correcte
Probing Neutrino low energy and mass scales
Low energy neutrino processes are ideal probes for new Physics beyond the
Standard Model. Cosmological observations and rare nuclear processes can test
neutrino mass scales and give definite answers to unsolved basic questions like
the Majorana/Dirac nature of the neutrino.Comment: 6 Pages, summary of the ``Probing low energy and mass scales''
session during the Neutrino Oscillation Workshop NOW2006, Otranto, Italy,
September 9-16 200
Limits on the Non-Standard Interactions of Neutrinos from Colliders
We provide an effective Lagrangian analysis of contact non-standard
interactions of neutrinos with electrons, which can be effectively mediated by
extra particles, and examine the associated experimental limits. At present,
such interactions are strongly constrained only for : the bounds are
loose for and absent for . We emphasize the unique role
played by the reaction in providing direct
constraints on such non-standard interactions.Comment: 15 LaTeX pages, 6 postscript figures, uses epsfig. New discussion on
bounds from reactor anti-neutrino scattering off electrons; minor changes. To
appear on Phys. Lett.
Neutrino mass bounds from cosmology
Cosmology is at present one of the most powerful probes of neutrino
properties. The advent of precision data from the cosmic microwave background
and large scale structure has allowed for a very strong bound on the neutrino
mass. Here, I review the status of cosmological bounds on neutrino properties
with emphasis on mass bounds on light neutrinos.Comment: 6 pages, 3 figures, talk given at NOW2004 workshop, Conca
Specchiulla, Italy, September 11-17, 200
Spontaneous baryogenesis in flat directions
We discuss a spontaneous baryogenesis mechanism in flat directions. After
identifying the Nambu-Goldstone mode which derivatively couples to the
associated (1) current and rotates due to the A-term, we show that
spontaneous baryogenesis can be naturally realized in the context of the flat
direction. As applications, we discuss two scenarios of baryogenesis in detail.
One is baryogenesis in a flat direction with a vanishing charge,
especially, with neither baryon nor lepton charge, which was recently proposed
by Chiba and the present authors. The other is a baryogenesis scenario
compatible with a large lepton asymmetry.Comment: 10 pages, no figure, the version accepted to Phys. Rev. D; a few
explanatory comments are adde
Probing oscillations into sterile neutrinos with cosmology, astrophysics and experiments
We perform a thorough analysis of oscillation signals generated by one extra
sterile neutrino, extending previous analyses done in simple limiting cases and
including the effects of established oscillations among active neutrinos. We
consider the following probes: solar, atmospheric, reactor and beam neutrinos,
Big-Bang Nucleosynthesis (helium-4, deuterium), Cosmic Microwave Background,
Large Scale Structure, supernovae, neutrinos from other astrophysical sources.
We find no evidence for a sterile neutrino in present data, identify the still
allowed regions, and study which future experiments can best probe them:
sub-MeV solar experiments, more precise studies of CMB or BBN, future supernova
explosions, etc. We discuss how the LSND hint is strongly disfavoured by the
constraints of (standard) cosmology.Comment: 50 pages, many (14) figures. The text is divided into "results" and
"technical details" sections. Final updated versio
Constraining dynamical dark energy with a divergence-free parametrization in the presence of spatial curvature and massive neutrinos
In this paper, we report the results of constraining the dynamical dark
energy with a divergence-free parameterization, , in the presence of spatial curvature and
massive neutrinos, with the 7-yr WMAP temperature and polarization data, the
power spectrum of LRGs derived from SDSS DR7, the Type Ia supernova data from
Union2 sample, and the new measurements of from HST, by using a MCMC
global fit method. Our focus is on the determinations of the spatial curvature,
, and the total mass of neutrinos, , in such a
dynamical dark energy scenario, and the influence of these factors to the
constraints on the dark energy parameters, and . We show that
and can be well constrained in this model; the 95% CL
limits are: and eV. Comparing to
the case in a flat universe, we find that the error in is amplified by
25.51%, and the error in is amplified by 0.14%; comparing to the case
with a zero neutrino mass, we find that the error in is amplified by
12.24%, and the error in is amplified by 1.63%.Comment: 5 pages, 2 figures; discussions added; accepted for publication in
Physics Letters
Could Large CP Violation Be Detected at Colliders?
We argue that CP--violation effects below a few tenths of a percent are
probably undetectable at hadron and electron colliders. Thus only operators
whose contributions interfere with tree--level Standard Model amplitudes are
detectable. We list these operators for Standard Model external particles and
some two and three body final state reactions that could show detectable
effects. These could test electroweak baryogenesis scenarios.Comment: 11pp, LaTeX, UM--TH--92--27(massaged to make TeX output cleaner), no
picture
Fluids in cosmology
We review the role of fluids in cosmology by first introducing them in
General Relativity and then by applying them to a FRW Universe's model. We
describe how relativistic and non-relativistic components evolve in the
background dynamics. We also introduce scalar fields to show that they are able
to yield an inflationary dynamics at very early times (inflation) and late
times (quintessence). Then, we proceed to study the thermodynamical properties
of the fluids and, lastly, its perturbed kinematics. We make emphasis in the
constrictions of parameters by recent cosmological probes.Comment: 34 pages, 4 figures, version accepted as invited review to the book
"Computational and Experimental Fluid Mechanics with Applications to Physics,
Engineering and the Environment". Version 2: typos corrected and references
expande
New Signatures for a Light Stop at LEP2 in SUSY Models with Spontaneously Broken R-Parity
In a class of supersymmetric models with R-parity breaking the lightest stop
can have new decay modes into third generation fermions, . We show that this decay may be dominant or at least
comparable to the ordinary R-parity conserving mode , where denotes the lightest neutralino.
The new R-parity violating decay mode could provide new signatures for stop
production at LEP.Comment: uudecoded latex file, 12 pages with 3 figures included. The complete
uudecoded ps paper is also available via anonymous ftp at
ftp://neutrinos.uv.es/pub/papers/ps/stop1.u
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