1,903 research outputs found
Right-Handed Sector Leptogenesis
Instead of creating the observed baryon asymmetry of the universe by the
decay of right-handed (RH) neutrinos to left-handed leptons, we propose to
generate it dominantly by the decay of the RH neutrinos to RH leptons. This
mechanism turns out to be successful in large regions of parameter space. It
may work, in particular, at a scale as low as ~TeV, with no need to
invoke quasi-degenerate RH neutrino masses to resonantly enhance the asymmetry.
Such a possibility can be probed experimentally by the observation at colliders
of a singlet charged Higgs particle and of RH neutrinos. Other mechanisms which
may lead to successful leptogenesis from the RH lepton sector interactions are
also briefly presented. The incorporation of these scenarios in left-right
symmetric and unified models is discussed.Comment: 14 pages, latex, axodraw; minor clarifications and references added,
extended discussion of the signatures at collider
Conformally Invariant Fractals and Potential Theory
The multifractal (MF) distribution of the electrostatic potential near any
conformally invariant fractal boundary, like a critical O(N) loop or a
-state Potts cluster, is solved in two dimensions. The dimension of the boundary set with local wedge angle is , with the central charge of the
model. As a corollary, the dimensions
of the external perimeter and of the hull of a Potts cluster obey
the duality equation . A related covariant
MF spectrum is obtained for self-avoiding walks anchored at cluster boundaries.Comment: 5 pages, 1 figur
Light Lepton Number Violating Sneutrinos and the Baryon Number of the Universe
Recent results of neutrino oscillation experiments point to a nonvanishing
neutrino mass. Neutrino mass models favour Majorana-type neutrinos. In such
circumstances it is natural that the supersymmetric counterpart of the
neutrino, the sneutrino, bears also lepton number violating properties. On the
other hand, the fact that the universe exhibits an asymmetry in the baryon and
antibaryon numbers poses constraints on the extent of lepton number violation
in the light sneutrino sector if the electroweak phase transition is second or
weak first order. From the requirement that the Baryon Asymmetry of the
Universe should not be washed out by sneutrino induced lepton number violating
interactions and sphalerons below the critical temperature of the electroweak
phase transition we find that the mass splitting of the light sneutrino mass
states is compatible with the sneutrino Cold Dark Matter hypothesis only for
heavy gauginos and opposite sign gaugino mass parameters.Comment: 13 pages, 4 figure
Exact Multifractal Exponents for Two-Dimensional Percolation
The harmonic measure (or diffusion field or electrostatic potential) near a
percolation cluster in two dimensions is considered. Its moments, summed over
the accessible external hull, exhibit a multifractal spectrum, which I
calculate exactly. The generalized dimensions D(n) as well as the MF function
f(alpha) are derived from generalized conformal invariance, and are shown to be
identical to those of the harmonic measure on 2D random walks or self-avoiding
walks. An exact application to the anomalous impedance of a rough percolative
electrode is given. The numerical checks are excellent. Another set of exact
and universal multifractal exponents is obtained for n independent
self-avoiding walks anchored at the boundary of a percolation cluster. These
exponents describe the multifractal scaling behavior of the average nth moment
of the probabity for a SAW to escape from the random fractal boundary of a
percolation cluster in two dimensions.Comment: 5 pages, 3 figures (in colors
Surface reconstruction induced geometries of Si clusters
We discuss a generalization of the surface reconstruction arguments for the
structure of intermediate size Si clusters, which leads to model geometries for
the sizes 33, 39 (two isomers), 45 (two isomers), 49 (two isomers), 57 and 61
(two isomers). The common feature in all these models is a structure that
closely resembles the most stable reconstruction of Si surfaces, surrounding a
core of bulk-like tetrahedrally bonded atoms. We investigate the energetics and
the electronic structure of these models through first-principles density
functional theory calculations. These models may be useful in understanding
experimental results on the reactivity of Si clusters and their shape as
inferred from mobility measurements.Comment: 9 figures (available from the author upon request) Submitted to Phys.
Rev.
Stringy instanton corrections to N=2 gauge couplings
We discuss a string model where a conformal four-dimensional N=2 gauge theory
receives corrections to its gauge kinetic functions from "stringy" instantons.
These contributions are explicitly evaluated by exploiting the localization
properties of the integral over the stringy instanton moduli space. The model
we consider corresponds to a setup with D7/D3-branes in type I' theory
compactified on T4/Z2 x T2, and possesses a perturbatively computable heterotic
dual. In the heteoric side the corrections to the quadratic gauge couplings are
provided by a 1-loop threshold computation and, under the duality map, match
precisely the first few stringy instanton effects in the type I' setup. This
agreement represents a very non-trivial test of our approach to the exotic
instanton calculus.Comment: 63 pages, 5 figures. V2: final version with minor corrections
published on JHEP05(2010)10
Social preferences, accountability, and wage bargaining
We assess the extent of preferences for employment in a collective wage bargaining situation with heterogeneous workers. We vary the size of the union and introduce a treatment mechanism transforming the voting game into an individual allocation task. Our results show that highly productive workers do not take employment of low productive workers into account when making wage proposals, regardless of whether insiders determine the wage or all workers. The level of pro-social preferences is small in the voting game, while it increases as the game is transformed into an individual allocation task. We interpret this as an accountability effect
Synchronization of chaotic oscillator time scales
This paper deals with the chaotic oscillator synchronization. A new approach
to detect the synchronized behaviour of chaotic oscillators has been proposed.
This approach is based on the analysis of different time scales in the time
series generated by the coupled chaotic oscillators. It has been shown that
complete synchronization, phase synchronization, lag synchronization and
generalized synchronization are the particular cases of the synchronized
behavior called as "time--scale synchronization". The quantitative measure of
chaotic oscillator synchronous behavior has been proposed. This approach has
been applied for the coupled Rossler systems.Comment: 29 pages, 11 figures, published in JETP. 100, 4 (2005) 784-79
Scaling, Multiscaling, and Nontrivial Exponents in Inelastic Collision Processes
We investigate velocity statistics of homogeneous inelastic gases using the
Boltzmann equation. Employing an approximate uniform collision rate, we obtain
analytic results valid in arbitrary dimension. In the freely evolving case, the
velocity distribution is characterized by an algebraic large velocity tail,
P(v,t) ~ v^{-sigma}. The exponent sigma(d,epsilon), a nontrivial root of an
integral equation, varies continuously with the spatial dimension, d, and the
dissipation coefficient, epsilon. Although the velocity distribution follows a
scaling form, its moments exhibit multiscaling asymptotic behavior.
Furthermore, the velocity autocorrelation function decays algebraically with
time, A(t)= ~ t^{-alpha}, with a non-universal dissipation-dependent
exponent alpha=1/epsilon. In the forced case, the steady state Fourier
transform is obtained via a cumulant expansion. Even in this case, velocity
correlations develop and the velocity distribution is non-Maxwellian.Comment: 10 pages, 3 figure
The UTfit Collaboration Average of D meson mixing data: Spring 2012
We derive constraints on the parameters , and
that describe meson mixing using all available data, allowing
for CP violation. We also provide posterior distributions and predictions for
observable parameters appearing in physics.Comment: 5 pages, 3 figure
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