2,033 research outputs found
Critical-layer structures and mechanisms in elastoinertial turbulence
Simulations of elastoinertial turbulence (EIT) of a polymer solution at low
Reynolds number are shown to display localized polymer stretch fluctuations.
These are very similar to structures arising from linear stability
(Tollmien-Schlichting (TS) modes) and resolvent analyses: i.e., critical-layer
structures localized where the mean fluid velocity equals the wavespeed.
Computation of self-sustained nonlinear TS waves reveals that the critical
layer exhibits stagnation points that generate sheets of large polymer stretch.
These kinematics may be the genesis of similar structures in EIT.Comment: 5 pages, 4 figures; Accepted in Physical Review Letter
Influence of Logging on Douglas Fir Beetle Populations
All species of bark beetles of economic importance prefer to attack freshly-killed host material. Logging slash, wind-throw, and fire-killed timber provide ideal breeding grounds for bark beetles. A few species, mostly in the Dendroctonus group, are able to kill living trees. When beetles in the group, raised in preferred host material, cannot find any or enough freshly-killed trees, logs, or slash to enter, they may attack living trees. In the interior of British Columbia, infestations of the Douglas fir beetle can often be traced to logging disturbance
Geometrical Finiteness, Holography, and the BTZ Black Hole
We show how a theorem of Sullivan provides a precise mathematical statement
of a 3d holographic principle, that is, the hyperbolic structure of a certain
class of 3d manifolds is completely determined in terms of the corresponding
Teichmuller space of the boundary. We explore the consequences of this theorem
in the context of the Euclidean BTZ black hole in three dimensions.Comment: 6 pages, Latex, Version to appear in Physical Review Letter
Non-uniqueness of ergodic measures with full Hausdorff dimension on a Gatzouras-Lalley carpet
In this note, we show that on certain Gatzouras-Lalley carpet, there exist
more than one ergodic measures with full Hausdorff dimension. This gives a
negative answer to a conjecture of Gatzouras and Peres
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