48,878 research outputs found
On time-inhomogeneous controlled diffusion processes in domains
Time-inhomogeneous controlled diffusion processes in both cylindrical and
noncylindrical domains are considered. Bellman's principle and its applications
to proving the continuity of value functions are investigated.Comment: Published at http://dx.doi.org/10.1214/009117906000000395 in the
Annals of Probability (http://www.imstat.org/aop/) by the Institute of
Mathematical Statistics (http://www.imstat.org
A simple model of gauged lepton and baryon charges
We argue that simpler fermionic contents, responsible for the extension of
the standard model with gauged lepton and baryon charges, can be constructed by
assuming existence of so-called leptoquarks (j,k) with exotic electric charges
q_j=1/2, q_k=-1/2. Some new features in our model are that (i) as the natural
consequences of anomaly cancelation the right-handed neutrinos exist, and the
number of the observed fermion families is equal to the number of the
fundamental colors; (ii) although the lepton and baryon charges are conserved,
the neutrinos can obtain small masses through the type I seesaw mechanism in
similarity to the standard context, and the baryogenesis can be generated in
several cases. They all are natural results due to the spontaneous breaking of
these charges. Some constraints on the new physics via flavor changing and
related phenomenologies such as the stable scalar with anomalous electric
charge and interested processes at colliders are also discussed.Comment: 13 pages, revised versio
Performance Improvement of Variable Speed Rotors by Gurney Flaps
Gurney flaps are used for improving the performance of variable speed rotors. An analytical model able to predict helicopter rotor power is first presented, and the flight data of the UH-60A helicopter is used for validation. The predictions of the rotor power are in good agreement with the flight test data, justifying the use of this tool in analyzing helicopter performance. A fixed Gurney flap can enhance the performance of variable speed rotors and expand the corresponding flight envelop, especially near stall and high speed flight. A retractable Gurney flap at 1/rev yields more power savings than a fixed Gurney flap or a retractable one with higher a harmonic prescribed motion. At a speed of 200km/h, the retractable Gurney flap at 1/rev can obtain 3.22% more power reduction at a rotor speed of 85% nominal rotor speed, and this value is 8.37% at a speed of 220km/h. The height corresponding to the minimum power increases slowly in low to medium speed flight, and increases dramatically in high speed flight. With increasing take-off weight (i.e. rotor thrust), the retractable Gurney flap at 1/rev can obtain more rotor power savings
Improving Stochastic Estimator Techniques for Disconnected Diagrams
Disconnected diagrams are expected to be sensitive to the inclusion of
dynamical fermions. We present a feasibility study for the observation of such
effects on the nucleonic matrix elements of the axial vector current, using
SESAM full QCD vacuum configurations with Wilson fermions on
lattices, at . Starting from the standard methods developed by the
Kentucky and Tsukuba groups, we investigate the improvement from various
refinements thereof.Comment: One author added. Contribution to Lattice 1997, 3 pages LaTex, to
appear in Nucl. Phys. B (Proc. Suppl.
Whittaker Modules for the twisted Heisenberg-Virasoro Algebra
We define Whittaker modules for the twisted Heisenberg-Virasoro algebra and
obtain analogues to several results from the classical setting, including a
classification of simple Whittaker modules by central characters.Comment: Latex, 18 pag
Recent Progress of Multiferroic Perovskite Manganites
Many multiferroic materials, with various chemical compositions and crystal
structures, have been discovered in the past years. Among these multiferroics,
some perovskite manganites with ferroelectricity driven by magnetic orders are
of particular interest. In these multiferroic perovskite manganites, not only
their multiferroic properties are quite prominent, but also the involved
physical mechanisms are very plenty and representative. In this Brief Review,
we will introduce some recent theoretical and experimental progress on
multiferroic manganites.Comment: 24 pages, 17 figures. A brief revie
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