936 research outputs found
The Matsumoto and Yor process and infinite dimensional hyperbolic space
The Matsumoto\,--Yor process is , where
is a Brownian motion. It is shown that it is the limit of the radial
part of the Brownian motion at the bottom of the spectrum on the hyperbolic
space of dimension , when tends to infinity. Analogous processes on
infinite series of non compact symmetric spaces and on regular trees are
described.Comment: 3
Pitman transforms and Brownian motion in the interval viewed as an affine alcove
Pitman's theorem states that if {Bt, t 0} is a one-dimensional Brownian
motion, then {Bt -- 2 inf st Bs, t 0} is a three dimensional Bessel
process, i.e. a Brownian motion conditioned in Doob sense to remain forever
positive. In this paper one gives a similar representation for the Brownian
motion in an interval. Due to the double barrier, it is much more involved and
only asymptotic. This uses the fact that the interval is an alcove of the
Affine Lie algebra A 1 1
Littelmann paths and brownian paths
We study some path transformations related to Littelmann path model and their
applications to representation theory and Brownian motion in a Weyl chamber.Comment: 30 pages, 1 figur
Intrinsic limits governing MBE growth of Ga-assisted GaAs nanowires on Si(111)
Diffusion-enhanced and desorption-limited growth regimes of Ga-assisted GaAs
nanowires were identified. In the latter regime, the number of vertical NWs
with a narrow length distribution was increased by raising the growth
temperature. The maximum axial growth rate; which can be quantified by the
supplied rate of As atoms, is achieved when a dynamical equilibrium state is
maintained in Ga droplets i.e. the number of impinging As atoms on the droplet
surface is equivalent to that of direct deposited Ga atoms combining with the
diffusing ones. The contribution of Ga diffusion to the wire growth was
evidenced by the diameter-dependent NW axial growth rate
On Eigenvalue spacings for the 1-D Anderson model with singular site distribution
We study eigenvalue spacings and local eigenvalue statistics for 1D lattice
Schrodinger operators with Holder regular potential, obtaining a version of
Minami's inequality and Poisson statistics for the local eigenvalue spacings.
The main additional new input are regular properties of the Furstenberg
measures and the density of states obtained in some of the author's earlier
work.Comment: 13 page
Overdoped Cuprates With High Temperature Superconducting Transitions
Evidence for High Tc cuprate superconductivity is found in a region of the
phase diagram where non-superconducting Fermi liquid metals are expected. Cu
valences estimated independently from both x-ray absorption near-edge structure
(XANES) and bond valence sum (BVS) measurements are > 2.3 for structures in the
homologous series (Cu0.75Mo0.25)Sr2(Y,Ce)sCu2O5+2s+{\delta} with s = 1, 2, 3,
and 4. The s = 1 member, (Cu0.75Mo0.25)Sr2YCu2O7+{\delta}, 0 \leq {\delta} \leq
0.5, is structurally related to YBa2Cu3O7 in which 25% of the basal Cu cations
[i.e. those in the chain layer] are replaced by Mo, and the Ba cations are
replaced by Sr. After oxidation under high pressure the s = 1 member becomes
superconducting with Tc = 88K. The Cu valence is estimated to be ~2.5, well
beyond the ~2.3 value for which other High-Tc cuprates are considered to be
overdoped Fermi liquids. The increase in valence is attributed to the
additional 0.5 oxygen ions added per chain upon oxidation. The record short
apical oxygen distance, at odds with current theory, suggests the possibility
of a new pairing mechanism but further experiments are urgently needed to
obtain more direct evidence. From the structural point of view the members with
s \geq 2 are considered to be equivalent to single-layer cuprates. All have Tc
~ 56 K which is significantly higher than expected because they also have
higher than expected Cu valences. The XANES-determined valences normalized to
give values in the CuO2 layers are 2.24, 2.25, and 2.26 for s = 2, 3, and 4,
while the BVS values determined for the valence in the CuO2 layer alone are
2.31-2.34 for the s = 2 and 3 members. No evidence for periodic ordering has
been detected by electron diffraction and high resolution imaging studies. The
possibility that the charge reservoir layers are able to screen long range
coulomb interactions and thus enhance Tc is discussed
Transport in the random Kronig-Penney model
The Kronig-Penney model with random Dirac potentials on the lattice \ZM has
critical energies at which the Lyapunov exponent vanishes and the density of
states has a van Hove singularity. This leads to a non-trivial quantum
diffusion even though the spectrum is known to be pure-point
Influence of the Oryza sativa genotype on the fertility and quantitative traits of F1 hybrids between the two cultivated rice species O. sativa L. and O. glaberrima Steud.
Des croisements ont été réalisés entre les deux espèces de riz cultivé, en utilisant un parent #Oryza glaberrima constant et 14 cultivars d'#O. sativa, dont 11 traditionnels africains. Les hybrides F1 ont été étudiés pour leur fertilité et des caractères quantitatifs. L'analyse de ces derniers a montré la position intermédiaire des F1S par rapport aux lignées parentales et l'héritabilité élevée de plusieurs caractères dont la densité de ramifications secondaires sur la panicule. Tous les hybrides F1 ont présenté une fertilité paniculaire nulle, et seule l'observation du pollen a permis de discriminer les différentes combinaisons. Les hybrides issus de deux cultivars d'#O. sativa introgressés par l'espèce sauvage #O. longistaminata se sont montrés particulièrement stériles. (Résumé d'auteur
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