320 research outputs found
Mixing-induced CP violating sources for electroweak baryogenesis from a semiclassical approach
The effects of flavor mixing in electroweak baryogenesis is investigated in a
generalized semiclassical WKB approach. Through calculating the nonadiabatic
corrections to the particle currents it is shown that extra CP violation
sources arise from the off-diagonal part of the equation of motion of particles
moving inside the bubble wall. This type of mixing-induced source is of the
first order in derivative expansion of the Higgs condensate, but is oscillation
suppressed. The numerical importance of the mixing-induced source is discussed
in the Minimal Supersymmetric Standard Model and compared with the source term
induced by semiclassical force. It is found that in a large parameter space
where oscillation suppression is not strong enough, the mixing-induced source
can dominate over that from the semiclassical force.Comment: 19 pp, 2 figs, 1 table, some comments added, to appear in
Eur.Phys.J.
Effects of Large CP-violating Soft Phases on Supersymmetric Electroweak Baryogenesis
We revisit the results of recent electroweak baryogenesis calculations and
include all allowed large CP-violating supersymmetric phases. If the phases are
large, the resulting baryon asymmetry can be considerably larger than the
observed value . Much of the asymmetry must
therefore be washed out, and we argue that the upper bound on the light Higgs
mass is larger than the value reported in previous work.Comment: 15 pages, 3 figure
The Baryon asymmetry in the Standard Model with a low cut-off
We study the generation of the baryon asymmetry in a variant of the standard
model, where the Higgs field is stabilized by a dimension-six interaction.
Analyzing the one-loop potential, we find a strong first order electroweak
phase transition for Higgs masses up to at least 170 GeV. Dimension-six
operators induce also new sources of CP violation. We compute the baryon
asymmetry in the WKB approximation. Novel source terms in the transport
equations enhance the generated baryon asymmetry. For a wide range of
parameters the model predicts a baryon asymmetry close to the observed value.Comment: 22 pages, latex, 6 figure
A Way to Reopen the Window for Electroweak Baryogenesis
We reanalyse the sphaleron bound of electroweak baryogenesis when allowing
deviations to the Friedmann equation. These modifications are well motivated in
the context of brane cosmology where they appear without being in conflict with
major experimental constraints on four-dimensional gravity. While suppressed at
the time of nucleosynthesis, these corrections can dominate at the time of the
electroweak phase transition and in certain cases provide the amount of
expansion needed to freeze out the baryon asymmetry without requiring a
strongly first order phase transition. The sphaleron bound is substantially
weakened and can even disappear so that the constraints on the higgs and stop
masses do not apply anymore. Such modification of cosmology at early times
therefore reopens the parameter space allowing electroweak baryogenesis which
had been reduced substantially given the new bound on the higgs mass imposed by
LEP. In contrast with previous attempts to turn around the sphaleron bound
using alternative cosmologies, we are still considering that the electroweak
phase transition takes place in a radiation dominated universe. The universe is
expanding fast because of the modification of the Friedmann equation itself
without the need for a scalar field and therefore evading the problem of the
decay of this scalar field after the completion of the phase transition and the
risk that its release of entropy dilutes the baryon asymmetry produced at the
transition.Comment: 19 pages, 3 figures; v2: minor changes, remark added at end of
section 5 and in caption of figure 1; v3: references added, version to be
publishe
Towards a Nonequilibrium Quantum Field Theory Approach to Electroweak Baryogenesis
We propose a general method to compute -violating observables from
extensions of the standard model in the context of electroweak baryogenesis. It
is alternative to the one recently developed by Huet and Nelson and relies on a
nonequilibrium quantum field theory approach. The method is valid for all
shapes and sizes of the bubble wall expanding in the thermal bath during a
first-order electroweak phase transition. The quantum physics of -violation
and its suppression coming from the incoherent nature of thermal processes are
also made explicit.Comment: 19 pages, 1 figure available upon e-mail reques
Transient domain walls and lepton asymmetry in the Left-Right symmetric model
It is shown that the dynamics of domain walls in Left-Right symmetric models,
separating respective regions of unbroken SU(2)_L and SU(2)_R in the early
universe, can give rise to baryogenesis via leptogenesis. Neutrinos have a
spatially varying complex mass matrix due to CP-violating scalar condensates in
the domain wall. The motion of the wall through the plasma generates a flux of
lepton number across the wall which is converted to a lepton asymmetry by
helicity-flipping scatterings. Subsequent processing of the lepton excess by
sphalerons results in the observed baryon asymmetry, for a range of parameters
in Left-Right symmetric models.Comment: v2 version accepted for publication in Phys. Rev. D. Discussion in
Introduction and Conclusion sharpened. Equation (12) corrected. 16 pages, 3
figure files, RevTeX4 styl
Electroweak Phase Transitions in left-right symmetric models
We study the finite-temperature effective potential of minimal left-right
symmetric models containing a bidoublet and two triplets in the scalar sector.
We perform a numerical analysis of the parameter space compatible with the
requirement that baryon asymmetry is not washed out by sphaleron processes
after the electroweak phase transition. We find that the spectrum of scalar
particles for these acceptable cases is consistent with present experimental
bounds.Comment: 20 pages, 5 figures (included), some comments added, typos corrected
and new references included. Final version to appear in PR
Noncommutative vector bundles over fuzzy CP^N and their covariant derivatives
We generalise the construction of fuzzy CP^N in a manner that allows us to
access all noncommutative equivariant complex vector bundles over this space.
We give a simplified construction of polarization tensors on S^2 that
generalizes to complex projective space, identify Laplacians and natural
noncommutative covariant derivative operators that map between the modules that
describe noncommuative sections. In the process we find a natural
generalization of the Schwinger-Jordan construction to su(n) and identify
composite oscillators that obey a Heisenberg algebra on an appropriate Fock
space.Comment: 34 pages, v2 contains minor corrections to the published versio
K-Space at TRECVID 2008
In this paper we describe K-Space’s participation in
TRECVid 2008 in the interactive search task. For 2008
the K-Space group performed one of the largest interactive
video information retrieval experiments conducted
in a laboratory setting. We had three institutions participating
in a multi-site multi-system experiment. In
total 36 users participated, 12 each from Dublin City
University (DCU, Ireland), University of Glasgow (GU,
Scotland) and Centrum Wiskunde and Informatica (CWI,
the Netherlands). Three user interfaces were developed,
two from DCU which were also used in 2007 as well as
an interface from GU. All interfaces leveraged the same
search service. Using a latin squares arrangement, each
user conducted 12 topics, leading in total to 6 runs per
site, 18 in total. We officially submitted for evaluation 3
of these runs to NIST with an additional expert run using
a 4th system. Our submitted runs performed around
the median. In this paper we will present an overview of
the search system utilized, the experimental setup and a
preliminary analysis of our results
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