26,631 research outputs found
Concentration dependence of the up- and down-conversion emission colours of Er3+-doped Y2O3: a time-resolved spectroscopy analysis
Er3+ energy transfer mechanisms and their influence on the dynamics and emission colours are considered for upconversion and downconversion regimes.</jats:p
Generalized hydrodynamics of a dilute finite-sized particles suspension: Dynamic viscosity
We present a mesoscopic hydrodynamic description of the dynamics of colloidal
suspensions. We consider the system as a gas of Brownian particles suspended in
a Newtonian heat bath subjected to stationary non-equilibrium conditions
imposed by a velocity field. Using results already obtained in previous studies
in the field by means of a generalized Fokker-Planck equation, we obtain a set
of coupled differential equations for the local diffusion current and the
evolution of the total stress tensor. We find that the dynamic shear viscosity
of the system contains contributions arising from the finite size of the
particles.Comment: To appear in Physical Review
Avoided crossing resonances: structural and dynamical aspects
We examine structural and dynamical properties of quantum resonances
associated with an avoided crossing and identify the parameter shifts where
these properties attain maximal or extreme values, first at a general level,
and then for a two-level system coupled to a harmonic oscillator, of the type
commonly found in quantum optics. Finally the results obtained are exemplified
and applied to optimize the fidelity and speed of quantum gates in trapped
ions.Comment: 4 pages, 1 figur
Superisolated Surface Singularities
In this survey, we review part of the theory of superisolated surface
singularities (SIS) and its applications including some new and recent
developments. The class of SIS singularities is, in some sense, the simplest
class of germs of normal surface singularities. Namely, their tangent cones are
reduced curves and the geometry and topology of the SIS singularities can be
deduced from them. Thus this class \emph{contains}, in a canonical way, all the
complex projective plane curve theory, which gives a series of nice examples
and counterexamples. They were introduced by I. Luengo to show the
non-smoothness of the -constant stratum and have been used to answer
negatively some other interesting open questions. We review them and the new
results on normal surface singularities whose link are rational homology
spheres. We also discuss some positive results which have been proved for SIS
singularities.Comment: Survey article for the Proceedings of the Conference "Singularities
and Computer Algebra" on Occasion of Gert-Martin Greuel's 60th Birthday, LMS
Lecture Notes (to appear
On piecewise isomorphism of some varieties
Two quasi-projective varieties are called piecewise isomorphic if they can be
stratified into pairwise isomorphic strata. We show that the m-th symmetric
power of the complex affine space is piecewise isomorphic to
and the m-th symmetric power of the infinite
dimensional complex projective space is piecewise isomorphic to the infinite
dimensional Grassmannian
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