1,322 research outputs found
On the Stability and the Approximation of Branching Distribution Flows, with Applications to Nonlinear Multiple Target Filtering
We analyse the exponential stability properties of a class of measure-valued
equations arising in nonlinear multi-target filtering problems. We also prove
the uniform convergence properties w.r.t. the time parameter of a rather
general class of stochastic filtering algorithms, including sequential Monte
Carlo type models and mean eld particle interpretation models. We illustrate
these results in the context of the Bernoulli and the Probability Hypothesis
Density filter, yielding what seems to be the first results of this kind in
this subject
Production and decays of supersymmetric Higgs bosons in spontaneously broken R-parity
We study the mass spectra, production and decay properties of the lightest
supersymmetric CP-even and CP-odd Higgs bosons in models with spontaneously
broken R-parity (SBRP). We compare the resulting mass spectra with expectations
of the Minimal Supersymmetric Standard Model (MSSM), stressing that the model
obeys the upper bound on the lightest CP-even Higgs boson mass. We discuss how
the presence of the additional scalar singlet states affects the Higgs
production cross sections, both for the Bjorken process and the "associated
production". The main phenomenological novelty with respect to the MSSM comes
from the fact that the spontaneous breaking of lepton number leads to the
existence of the majoron, denoted J, which opens new decay channels for
supersymmetric Higgs bosons. We find that the invisible decays of CP-even
Higgses can be dominant, while those of the CP-odd bosons may also be sizeable.Comment: 21 pages, 8 figures; minor changes, final version for publicatio
Degenerate neutrinos from a supersymmetric A_4 model
We investigate the supersymmetric A_4 model recently proposed by Babu, Ma and
Valle. The model naturally gives quasi-degenerate neutrinos that are bi-largely
mixed, in agreement with observations. Furthermore, the mixings in the quark
sector are constrained to be small, making it a complete model of the flavor
structure. Moreover, it has the interesting property that CP-violation in the
leptonic sector is maximal (unless vanishing). The model exhibit a close
relation between the slepton and lepton sectors and we derive the slepton
spectra that are compatible with neutrino data and the present bounds on
flavor-violating charged lepton decays. The prediction for the branching ratio
of the decay tau -> mu gamma has a lower limit of 10^{-9}. In addition, the
overall neutrino mass scale is constrained to be larger than 0.3 eV. Thus, the
model will be tested in the very near future.Comment: 11 pages, 6 figures. Talk given at the International Workshop on
Astroparticle and High Energy Physics (AHEP), Valencia, Spain, 14-18 Oct.
200
Minimal supergravity radiative effects on the tri-bimaximal neutrino mixing pattern
We study the stability of the Harrison-Perkins-Scott (HPS) mixing pattern,
assumed to hold at some high energy scale, against supersymmetric radiative
corrections. We work in the framework of a reference minimal supergravity model
(mSUGRA) where supersymmetry breaking is universal and flavor-blind at
unification. The radiative corrections considered include both RGE running as
well as threshold effects. We find that in this case the solar mixing angle can
only increase with respect to the HPS reference value, while the atmospheric
and reactor mixing angles remain essentially stable. Deviations from the solar
angle HPS prediction towards lower values would signal novel contributions from
physics beyond the simplest mSUGRA model.Comment: 13 pages, 3 figures; added reference; final version for publicatio
The Minimally Immersed 4D Supermembrane
n this note we summarize some of the properties found in [1], and its relation with [2]. We comment on the construction of the action of the 11D supermembrane with nontrivial central charges minimally immersed on a 7D toroidal manifold is obtained (MIM2).The transverse coordinates to the supermembrane are maps to a 4D Minkowski space-time. The action is invariant under additional symmetries in comparison to the supermembrane on a 11D Minkowski target space. The hamiltonian in the LCG is invariant under conformal transformations on the Riemann surface base manifold. The spectrum of the regularized hamiltonian is discrete with finite multiplicity. Its resolvent is compact. Susy is spontaneously broken, due to the topological central charge condition, to four supersymmetries in 4D, the vacuum belongs to an N=1 supermultiplet. When assuming the target-space to be an isotropic 7-tori, the potential does not contain any flat direction, it is stable on the moduli space of parameters. Moreover due to the discrete symmetries of the hamiltonian, there are only 7 possible minimal holomorphic immersions of the MIM2 on the 7-torus. When these symmetries are identified on the target space, it corresponds to compactify the MIM2 on a orbifold with G2 structure. Once the singularities are resolved it leads to the compactification of the MIM2 on a G2 manifold as shown in [2]
A Review of Soil-Improving Cropping Systems for Soil Salinization
A major challenge of the Sustainable Development Goals linked to Agriculture, Food Security, and Nutrition, under the current global crop production paradigm, is that increasing crop yields often have negative environmental impacts. It is therefore urgent to develop and adopt optimal soil-improving cropping systems (SICS) that can allow us to decouple these system parameters. Soil salinization is a major environmental hazard that limits agricultural potential and is closely linked to agricultural mismanagement and water resources overexploitation, especially in arid climates. Here we review literature seeking to ameliorate the negative effect of soil salinization on crop productivity and conduct a global meta-analysis of 128 paired soil quality and yield observations from 30 studies. In this regard, we compared the effectivity of different SICS that aim to cope with soil salinization across 11 countries, in order to reveal those that are the most promising. The analysis shows that besides case-specific optimization of irrigation and drainage management, combinations of soil amendments, conditioners, and residue management can contribute to significant reductions of soil salinity while significantly increasing crop yields. These results highlight that conservation agriculture can also achieve the higher yields required for upscaling and sustaining crop production
- …