30,626 research outputs found
Electroweak Baryogenesis in a Two-Higgs Doublet Model
Electroweak baryogenesis fails in the SM because of too small CP violation
and the lack of a strong first-order phase transition. It has been shown that
supersymmetric models allow for successful baryogenesis, where the Higgsinos
play an important role in the transport processes that generate the asymmetry.
I will demonstrate that also non-supersymmetric models can provide the observed
baryon asymmetry. The top quark takes the role of the Higgsinos. Focusing on
the two-Higgs doublet model, I will discuss details of the phase transition and
consequences for Higgs physics and EDM searches.Comment: 5 pages, 2 figures. Proceedings of Moriond 2006, Electroweak Session.
11-18 March, La Thuile (Italy
ON THE EXISTENCE OF STABLE EQUILIBRIA IN AGRICULTURE
Problems of instability and disequilibrium in U.S. agriculture are synthesized within a single conceptual framework. Agricultural and non-agricultural sector offer curves are used to illustrate why it may not be feasible to achieve and maintain equilibrium and price stability in U.S. agriculture. Empirical evidence on resource disequilibrium and instability in the ratio of prices paid and received by farmers is presented.Instability, Disequilibrium, Offer curves, U.S. agriculture, Policy, Demand and Price Analysis,
CRITICAL DEVELOPMENT ISSUES IN RURAL ECONOMIES
Community/Rural/Urban Development,
The bubble wall velocity in the minimal supersymmetric light stop scenario
We build on existing calculations of the wall velocity of the expanding
bubbles of the broken symmetry phase in a first-order electroweak phase
transition within the light stop scenario (LSS) of the MSSM. We carry out the
analysis using the 2-loop thermal potential for values of the Higgs mass
consistent with present experimental bounds. Our approach relies on describing
the interaction between the bubble and the hot plasma by a single friction
parameter, which we fix by matching to an existing 1-loop computation and
extrapolate it to our regime of interest. For a sufficiently strong phase
transition (in which washout of the newly-created baryon asymmetry is
prevented) we obtain values of the wall velocity, v_w~0.05, far below the speed
of sound in the medium, and not very much deviating from the previous 1-loop
calculation. We also find that the phase transition is about 10% stronger than
suggested by simply evaluating the thermal potential at the critical
temperature.Comment: 17pages, 3 figure
Muller's ratchet with overlapping generations
Muller's ratchet is a paradigmatic model for the accumulation of deleterious
mutations in a population of finite size. A click of the ratchet occurs when
all individuals with the least number of deleterious mutations are lost
irreversibly due to a stochastic fluctuation. In spite of the simplicity of the
model, a quantitative understanding of the process remains an open challenge.
In contrast to previous works, we here study a Moran model of the ratchet with
overlapping generations. Employing an approximation which describes the fittest
individuals as one class and the rest as a second class, we obtain closed
analytical expressions of the ratchet rate in the rare clicking regime. As a
click in this regime is caused by a rare large fluctuation from a metastable
state, we do not resort to a diffusion approximation but apply an approximation
scheme which is especially well suited to describe extinction events from
metastable states. This method also allows for a derivation of expressions for
the quasi-stationary distribution of the fittest class. Additionally, we
confirm numerically that the formulation with overlapping generations leads to
the same results as the diffusion approximation and the corresponding
Wright-Fisher model with non-overlapping generations
Phase Lags in the Optical-Infrared Light Curves of AGB Stars
To search for phase lags in the optical-infrared light curves of asymptotic
giant branch stars, we have compared infrared data from the COBE DIRBE
satellite with optical light curves from the AAVSO and other sources. We found
17 examples of phase lags in the time of maximum in the infrared vs. that in
the optical, and 4 stars with no observed lags. There is a clear difference
between the Mira variables and the semi-regulars in the sample, with the
maximum in the optical preceding that in the near-infrared in the Miras, while
in most of the semi-regulars no lags are observed. Comparison to published
theoretical models indicates that the phase lags in the Miras are due to strong
titanium oxide absorption in the visual at stellar maximum, and suggests that
Miras pulsate in the fundamental mode, while at least some semi-regulars are
first overtone pulsators. There is a clear optical-near-infrared phase lag in
the carbon-rich Mira V CrB; this is likely due to C2 and CN absorption
variations in the optical.Comment: AJ, in pres
Baryogenesis at the Electroweak Phase Transition for a SUSY Model with a Gauge Singlet
SUSY models with a gauge singlet easily allow for a strongly first order
electroweak phase transition (EWPT). We discuss the wall profile, in particular
transitional CP violation during the EWPT. We calculate CP violating source
terms for the charginos in the WKB approximation and solve the relevant
transport equations to obtain the generated baryon asymmetry.Comment: 5 pages, 6 figures. To appear in the Proceedings of Strong and
Electroweak Matter 2000 (SEWM2000), Marseilles; a reference adde
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