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Instability of supersymmetric microstate geometries
(SpringerJournal of High Energy Physics, 2016-10-07)
We investigate the classical stability of supersymmetric, asymptotically flat, microstate geometries with five non-compact dimensions. Such geometries admit an “evanescent ergosurface”: a timelike hypersurface of infinite ...
Robust identification of dynamically distinct regions in stratified turbulence
(Cambridge University PressJournal of Fluid Mechanics, 2016-10-18)
We present a new robust method for identifying three dynamically distinct regions in a stratified turbulent flow, which we characterise as quiescent flow, intermittent layers and turbulent patches. The method uses the ...
Fluid dynamics at the scale of the cell
(Cambridge University PressJournal of Fluid Mechanics, 2016-10-17)
The world of cellular biology provides us with many fascinating fluid dynamical phenomena that lie at the heart of physiology, development, evolution and ecology. Advances in imaging, micromanipulation and microfluidics ...
Learning parametrised regularisation functions via quotient minimisation
(WileyProceedings in Applied Mathematics and Mechanics, 2016-10-25)
We propose a novel strategy for the computation of adaptive regularisation functions. The general strategy consists of minimising the ratio of a parametrised regularisation function; the numerator contains the regulariser ...
Stresslets Induced by Active Swimmers
(American Physical SocietyPhysical Review Letters, 2016-09-30)
Active particles disturb the fluid around them as force dipoles, or stresslets, which govern their collective dynamics. Unlike swimming speeds, the stresslets of active particles are rarely determined due to the lack of a ...
New Target for Cosmic Axion Searches
(American Physical SocietyPhysical Review Letters, 2016-10-20)
Future cosmic microwave background experiments have the potential to probe the density of relativistic species at the subpercent level. This sensitivity allows light thermal relics to be detected up to arbitrarily high ...
On the Absence of Uniform Recovery in Many Real-World Applications of Compressed Sensing and the Restricted Isometry Property and Nullspace Property in Levels
(Society for Industrial and Applied MathematicsSiam Journal on Imaging Sciences, 2017-03-15)
The purpose of this paper is twofold. The first is to point out that the property of uniform recovery, meaning that all sparse vectors are recovered, does not hold in many applications where compressed sensing is successfully ...
Mobility of an axisymmetric particle near an elastic interface
(Cambridge University PressJournal of Fluid Mechanics, 2017-01-01)
Using a fully analytical theory, we compute the leading-order corrections to the translational, rotational and translation–rotation coupling mobilities of an arbitrary axisymmetric particle immersed in a Newtonian fluid ...
Nonlinear effects in buoyancy-driven variable-density turbulence
(Cambridge University PressJournal of Fluid Mechanics, 2017-01-01)
We consider the time dependence of a hierarchy of scaled L²ᵐ-norms D_m,ω and D_m,θ of the vorticity ω =∇ x u and the density gradient ∇θ, where θ = log.(ρ*/ ρ*₀), in a buoyancy-driven turbulent flow as simulated by Livescu ...
Long-range interactions, wobbles, and phase defects in chains of model cilia
(American Physical SoceityPhysical Review Fluids, 2016-12-13)
Eukaryotic cilia and flagella are chemo-mechanical oscillators capable of generating long-range coordinated motions known as metachronal waves. Pair synchronization is a fundamental requirement for these collective dynamics, ...