1,627 research outputs found
Observations of the Vortex Ring State
This paper considers the vortex ring state, a flow condition usually associated with the descent of a rotor into its own wake.
The phenomenon is investigated through experiments on simple rotor systems, and a comparison is then made with observations
of a flow generated by a specially designed open core, annular jet that generates a mean flow velocity profile similar to the mean
flow in a rotor wake in hover. In an experimentally simulated descent, the jet flow generates a flow state that shares many
features of the rotor vortex ring state
On the local eigenvalue statistics for random band matrices in the localization regime
We study local eigenvalue statistics associated with
one-dimensional, random band matrices with independent,
identically distributed, random variables and band width growing as ,
for . We consider the limit points associated with
the random variables , for . Our
general result states that, under localization bounds and a weak Wegner
estimate, any nontrivial limit points are distributed according to a compound
Poisson point process. Furthermore, assuming localization bounds and strong
Wegner and Minami estimates, we prove that this family of random variables has
nontrivial limit points for almost every , and that these limit
points are Poisson distributed with positive intensities. The assumptions hold
for Gaussian distributed random variables with
(\cite{schenker, peled, et. al.}), although it is expected that localization
bounds hold for . Some related results under
weaker hypotheses are presented
Convergence of resonances on thin branched quantum wave guides
We prove an abstract criterion stating resolvent convergence in the case of
operators acting in different Hilbert spaces. This result is then applied to
the case of Laplacians on a family X_\eps of branched quantum waveguides.
Combining it with an exterior complex scaling we show, in particular, that the
resonances on X_\eps approximate those of the Laplacian with ``free''
boundary conditions on , the skeleton graph of X_\eps.Comment: 48 pages, 1 figur
- …