659 research outputs found
Satellite potentials for hypergeometric Natanzon potentials
As a result of the so(2,1) of the hypergeometric Natanzon potential a set of
potentials related to the given one is determined. The set arises as a result
of the action of the so(2,1) generators.Comment: 9 page
The synthesis and properties of the phases obtained by solid-solid reactions
The presented work encompasses the subject of the studies and the results obtained over the last years by the research workers of the Department of Inorganic Chemistry. They include mainly the studies on the reactivity of metal oxides, searching for new phases in binary and ternary systems of metal oxides as well as describing phase relations establishing in such systems. They also encompass works on the extensive characteristics of physico-chemical properties of the newly obtained compounds
Nonparametric estimation of conditional transition probabilities in a non-Markov illness-death model
One important goal in multi-state modeling is the estimation of transition
probabilities. In longitudinal medical studies these quantities are particularly
of interest since they allow for long-term predictions of the process. In recent years
signi ficant contributions have been made regarding this topic. However, most of
the approaches assume independent censoring and do not account for the influence
of covariates. The goal of the paper is to introduce feasible estimation methods for
the transition probabilities in an illness-death model conditionally on current or
past covariate measures. All approaches are evaluated through a simulation study,
leading to a comparison of two di erent estimators. The proposed methods are
illustrated using real a colon cancer data set.This research was nanced by FEDER Funds through Programa Operacional
Factores de Competitividade COMPETE and by Portuguese Funds through FCT
- Funda ção para a CĂȘncia e a Tecnologia, within Projects Est-C/MAT/UI0013/2011 and
PTDC/MAT/104879/2008. We also acknowledge nancial support from the project Grants
MTM2008-03129 and MTM2011-23204 (FEDER support included) of the Spanish Ministerio
de Ciencia e Innovaci on and 10PXIB300068PR of the Xunta de Galicia. Partial support from
a grant from the US National Security Agency (H98230-11-1-0168) is greatly appreciated
Interaction of matter-wave gap solitons in optical lattices
We study mobility and interaction of gap solitons in a Bose-Einstein
condensate (BEC) confined by an optical lattice potential. Such localized
wavepackets can exist only in the gaps of the matter-wave band-gap spectrum and
their interaction properties are shown to serve as a measure of discreteness
imposed onto a BEC by the lattice potential. We show that inelastic collisions
of two weakly localized near-the-band-edge gap solitons provide simple and
effective means for generating strongly localized in-gap solitons through
soliton fusion.Comment: 12 pages, 7 figure
Quantum switches and quantum memories for matter-wave lattice solitons
We study the possibility of implementing a quantum switch and a quantum
memory for matter wave lattice solitons by making them interact with
"effective" potentials (barrier/well) corresponding to defects of the optical
lattice. In the case of interaction with an "effective" potential barrier, the
bright lattice soliton experiences an abrupt transition from complete
transmission to complete reflection (quantum switch) for a critical height of
the barrier. The trapping of the soliton in an "effective" potential well and
its release on demand, without loses, shows the feasibility of using the system
as a quantum memory. The inclusion of defects as a way of controlling the
interactions between two solitons is also reported
New Exactly Solvable Two-Dimensional Quantum Model Not Amenable to Separation of Variables
The supersymmetric intertwining relations with second order supercharges
allow to investigate new two-dimensional model which is not amenable to
standard separation of variables. The corresponding potential being the
two-dimensional generalization of well known one-dimensional P\"oschl-Teller
model is proven to be exactly solvable for arbitrary integer value of parameter
all its bound state energy eigenvalues are found analytically, and the
algorithm for analytical calculation of all wave functions is given. The shape
invariance of the model and its integrability are of essential importance to
obtain these results.Comment: 23 page
Harmonic oscillator with nonzero minimal uncertainties in both position and momentum in a SUSYQM framework
In the context of a two-parameter deformation of the
canonical commutation relation leading to nonzero minimal uncertainties in both
position and momentum, the harmonic oscillator spectrum and eigenvectors are
determined by using techniques of supersymmetric quantum mechanics combined
with shape invariance under parameter scaling. The resulting supersymmetric
partner Hamiltonians correspond to different masses and frequencies. The
exponential spectrum is proved to reduce to a previously found quadratic
spectrum whenever one of the parameters , vanishes, in which
case shape invariance under parameter translation occurs. In the special case
where , the oscillator Hamiltonian is shown to coincide
with that of the q-deformed oscillator with and its eigenvectors are
therefore --boson states. In the general case where , the eigenvectors are constructed as linear combinations of
--boson states by resorting to a Bargmann representation of the latter
and to -differential calculus. They are finally expressed in terms of a
-exponential and little -Jacobi polynomials.Comment: LaTeX, 24 pages, no figure, minor changes, additional references,
final version to be published in JP
Charged particle production in the Pb+Pb system at 158 GeV/c per nucleon
Charged particle multiplicities from high multiplicity central interactions
of 158 GeV/nucleon Pb ions with Pb target nuclei have been measured in the
central and far forward projectile spectator regions using emulsion chambers.
Multiplicities are significantly lower than predicted by Monte Carlo
simulations. We examine the shape of the pseudorapidity distribution and its
dependence on centrality in detail.Comment: 17 pages text plus 12 figures in postscript 12/23/99 -- Add TeX
version of sourc
Dirichlet sigma models and mean curvature flow
The mean curvature flow describes the parabolic deformation of embedded
branes in Riemannian geometry driven by their extrinsic mean curvature vector,
which is typically associated to surface tension forces. It is the gradient
flow of the area functional, and, as such, it is naturally identified with the
boundary renormalization group equation of Dirichlet sigma models away from
conformality, to lowest order in perturbation theory. D-branes appear as fixed
points of this flow having conformally invariant boundary conditions. Simple
running solutions include the paper-clip and the hair-pin (or grim-reaper)
models on the plane, as well as scaling solutions associated to rational (p, q)
closed curves and the decay of two intersecting lines. Stability analysis is
performed in several cases while searching for transitions among different
brane configurations. The combination of Ricci with the mean curvature flow is
examined in detail together with several explicit examples of deforming curves
on curved backgrounds. Some general aspects of the mean curvature flow in
higher dimensional ambient spaces are also discussed and obtain consistent
truncations to lower dimensional systems. Selected physical applications are
mentioned in the text, including tachyon condensation in open string theory and
the resistive diffusion of force-free fields in magneto-hydrodynamics.Comment: 77 pages, 21 figure
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