79,198 research outputs found
Recent progress in random metric theory and its applications to conditional risk measures
The purpose of this paper is to give a selective survey on recent progress in
random metric theory and its applications to conditional risk measures. This
paper includes eight sections. Section 1 is a longer introduction, which gives
a brief introduction to random metric theory, risk measures and conditional
risk measures. Section 2 gives the central framework in random metric theory,
topological structures, important examples, the notions of a random conjugate
space and the Hahn-Banach theorems for random linear functionals. Section 3
gives several important representation theorems for random conjugate spaces.
Section 4 gives characterizations for a complete random normed module to be
random reflexive. Section 5 gives hyperplane separation theorems currently
available in random locally convex modules. Section 6 gives the theory of
random duality with respect to the locally convex topology and in
particular a characterization for a locally convex module to be
prebarreled. Section 7 gives some basic results on convex
analysis together with some applications to conditional risk measures. Finally,
Section 8 is devoted to extensions of conditional convex risk measures, which
shows that every representable type of conditional convex risk
measure and every continuous type of convex conditional risk measure
() can be extended to an type
of lower semicontinuous conditional convex risk measure and an
type of continuous
conditional convex risk measure (), respectively.Comment: 37 page
\Lambda_b \to \Lambda_c P(V) Nonleptonic Weak Decays
The two-body nonleptonic weak decays of \Lambda_b \to \Lambda_c P(V) (P and V
represent pseudoscalar and vector mesons respectively) are analyzed in two
models, one is the Bethe-Salpeter (B-S) model and the other is the hadronic
wave function model. The calculations are carried out in the factorization
approach. The obtained results are compared with other model calculations.Comment: 18 pages, Late
Optimal design of an aeroelastic wing structure with seamless control surfaces
This article presents an investigation into the concept and optimal design of a lightweight seamless aeroelastic wing (SAW) structure for small air vehicles. Attention has been first focused on the design of a hingeless flexible trailing edge (TE) control surface. Two innovative design features have been created in the SAW TE section: an open sliding TE and a curved beam and disc actuation mechanism. This type of actuated TE section allows for the SAW having a camber change in a desirable shape and minimum control power demand. This design concept has been simulated numerically and demonstrated by a test model. For a small air vehicle of large sweep back wing, it is noted that significant structural weight saving can be achieved. However, further weight saving is mainly restricted by the aeroelastic stability and minimum number of carbon/epoxy plies in a symmetric layup rather than the structural strength. Therefore, subsequent effort was made to optimize the primary wing box structure. The results show that an initial structural weight can be reduced significantly under the strength criterion. The resulting reduction of the wing box stiffness and aeroelastic stability and control effectiveness can be improved by applying the aeroelastic tailoring. Because of the large swept angle and resulting lightweight and highly flexible SAW, geometrical non-linearity and large bending-torsion aeroelastic coupling have been considered in the analysis
Families of weighted sum formulas for multiple zeta values
Euler's sum formula and its multi-variable and weighted generalizations form
a large class of the identities of multiple zeta values. In this paper we prove
a family of identities involving Bernoulli numbers and apply them to obtain
infinitely many weighted sum formulas for double zeta values and triple zeta
values where the weight coefficients are given by symmetric polynomials. We
give a general conjecture in arbitrary depth at the end of the paper.Comment: The conjecture at the end is reformulate
Modeling Magnetic Field Structure of a Solar Active Region Corona using Nonlinear Force-Free Fields in Spherical Geometry
We test a nonlinear force-free field (NLFFF) optimization code in spherical
geometry using an analytical solution from Low and Lou. Several tests are run,
ranging from idealized cases where exact vector field data are provided on all
boundaries, to cases where noisy vector data are provided on only the lower
boundary (approximating the solar problem). Analytical tests also show that the
NLFFF code in the spherical geometry performs better than that in the Cartesian
one when the field of view of the bottom boundary is large, say, . Additionally, We apply the NLFFF model to an active region
observed by the Helioseismic and Magnetic Imager (HMI) on board the Solar
Dynamics Observatory (SDO) both before and after an M8.7 flare. For each
observation time, we initialize the models using potential field source surface
(PFSS) extrapolations based on either a synoptic chart or a flux-dispersal
model, and compare the resulting NLFFF models. The results show that NLFFF
extrapolations using the flux-dispersal model as the boundary condition have
slightly lower, therefore better, force-free and divergence-free metrics, and
contain larger free magnetic energy. By comparing the extrapolated magnetic
field lines with the extreme ultraviolet (EUV) observations by the Atmospheric
Imaging Assembly (AIA) on board SDO, we find that the NLFFF performs better
than the PFSS not only for the core field of the flare productive region, but
also for large EUV loops higher than 50 Mm.Comment: 34 pages, 8 figures, accepted for publication in Ap
Hybridization gap versus hidden order gap in URuSi as revealed by optical spectroscopy
We present the in-plane optical reflectance measurement on single crystals of
URuAs. The study revealed a strong temperature-dependent spectral
evolution. Above 50 K, the low frequency optical conductivity is rather flat
without a clear Drude-like response, indicating a very short transport life
time of the free carriers. Well below the coherence temperature, there appears
an abrupt spectral weight suppression below 400 cm, yielding evidence
for the formation of a hybridization energy gap arising from the mixing of the
conduction electron and narrow f-electron bands. A small part of the suppressed
spectral weight was transferred to the low frequency side, leading to a narrow
Drude component, while the majority of the suppressed spectral weight was
transferred to the high frequency side centered near 4000 cm. Below the
hidden order temperature, another very prominent energy gap structure was
observed, which leads to the removal of a large part of the Drude component and
a sharp reduction of the carrier scattering rate. The study revealed that the
hybridization gap and the hidden orger gap are distinctly different: they occur
at different energy scales and exhibit completely different spectral
characteristics.Comment: 5 page
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