Events Archive

Apr
03
2012
Einstein Toolkit Workshop - April 3rd - April 6th
The workshop will provide a general introduction into numerical relativity and in code development within large collaborations.  The number of addendees are limited, and while registration is free, it is required. In order to register, write an email to workshop@einsteintoolkit.org.  
Apr
03
2012
Geodesic Theory of Transport Barriers
I describe a unified approach to locating key material transport barriers in unsteady flows induced by two-dimensional, non-autonomous dynamical systems. Seeking transport barriers as minimally stretching material lines, one obtains that such barriers must be shadowed by minimal geodesics under the metric induced by the Cauchy-Green strain tensor field associated with the flow map. As a result, snapshots of transport barriers can be explicitly computed as trajectories of ordinary differential equations. Using this approach, hyperbolic barriers (generalized stable and unstable manifolds), elliptic barriers (generalized KAM curves) and parabolic barriers (...
Apr
02
2012
Building the Brookhaven (Homestake Gold Mine) Solar Neutrino Detector
A neutrino detector, capable of detecting the neutrinos from the Sun’s fusion cycle, was strongly requested by the Theorists working on the Solar Model in the early 1960’s.  The Cl37 → Ar37 detector scheme used by Davis and Harmer at the Savannah River Experiment in the 1950’s was suggested as the basis for a scaled up Solar Neutrino Detector. The details of the design and engineering of this scale up from “Laboratory” to “Production” one mile underground at the Homestake Gold Mine in...
Apr
02
2012
A Computational Approach to Understanding Cardiac Arrhythmias
Apr
02
2012
New Opportunities at the Advanced Light Source: Using Intermediate-Energy X-rays To Investigate Collective Behavior in Interacting Electron Systems
Mar
29
2012
Chemical doping effects in topological insulators
Topological insulators, a novel kind of three-dimensional insulators can have a bulk insulating gap but non-trivial topological surface states. The surface states of these topological insulators show Dirac-like behavior with the spin polarization locked perpendicular to the electron momentum by the effect of strong spin-orbit interaction. As the locking protects the surface electrons from back scattering, they are predicted to have high mobilities. The surface state of Bi2Se3 and Bi2Te3 topological insulators has been observed by angle-resolved...
Mar
27
2012
Wet Drop Impact
When a fast moving drop collides with a layer of fluid it a produces a splash, a spray of secondary droplets.  There is a bewildering variety of splash morphologies and droplet distributions which manifest as the system parameters (droplet size and speed, layer depth, fluid properties) are varied.  Despite this complexity, a splash begins with the formation of a sheet-like jet.  There are at least two varieties of jets: the large and slow lamella jet and the small and quick ejecta jet.  In this talk I will present our progress towards understanding the simplest of splashes, the so-called crown splash, which results from the disintegration...
Mar
26
2012
"Smectics!"
The homotopy theory of topological defects in ordered media fails to completely characterize systems with broken translational symmetry. We argue that the problem can be understood in terms of the lack of rotational Goldstone modes in such systems and provide an alternate approach that correctly accounts for the interaction between translations and rotations. Dislocations are associated, as usual, with branch points in a phase field, whereas disclinations arise as critical points and singularities in the phase field. We introduce a three-dimensional model for two-dimensional smectics that clarifies the topology of disclinations and geometrically captures...
Mar
26
2012
Got symmetry? Here is how you slice it
With recent advances in experimental imaging, computational methods, and dynamics insights it is now possible to start charting out the terra incognita explored by turbulence in strongly nonlinear classical field theories, such as fluid flows. In presence of continuous symmetries these solutions sweep out 2- and higher-dimensional manifolds (group orbits) of physically equivalent states, interconnected by a web of still higher-dimensional stable/unstable manifolds, all embedded in the PDE infinite-dimensional state spaces. In order to chart such invariant manifolds, one must first quotient the symmetries, i.e. replace the dynamics on M by an equivalent, symmetry reduced flow on M/G, in...
Mar
22
2012
Gamma-Ray Bursts as Tools for Extragalactic Astrophysics and Cosmology
Gamma-Ray Bursts (GRBs) are the brightest light sources in the Universe, as well as the most distant sources known. These characteristics, combined with their powerlaw spectra, make them ideal cosmological probes. In this talk I will discuss how GRBs are impacting several areas of extragalactic astrophysics and cosmology. In particular, I will show how they can be used to trace the evolution of the mean density and clumpiness of the interstellar medium with redshift, and the properties of dust in high-z galaxies. Detection of GRBs at very high redshifts can help set constraints on the small-scale power spectrum of density fluctuations. High-resolution observations of long GRBs...

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