Physics Colloquia Fall 2013

(usually Fridays 2:00 PM in SE 319)

Titles link to the abstracts.

Date Speaker Title
Sep 13
George Reifenberger
Sep 20
Zhongwei Li
Oct 18
Gerardo Estrada
Oct 25
Elsad Allahyarov
Case Western Reserve University
Nov 15
Andy Lau
Nov 22
Maurizio Giannotti
(Barry University)

Colloquium Abstracts

Binary Black Hole Mergers: Alternatives to Standard Puncture Initial Data and the Impact on Gravitational Waveforms
George Reifenberger (FAU), Sep 13
We study the evolution of binary black hole initial data schemes as alternatives to the standard puncture construction. These alternatives are based on post-Newtonian expansions that contain realistic gravitational waves. The first scheme is based on a second order post-Newtonian expansion in Arnowitt, Deser, and Misner transverse-traceless (ADMTT)gauge that has been re-summed to approach standard puncture data at the black holes. The other schemes are based on asymptotic matching of the 4-metrics of two tidally perturbed Schwarzschild solutions to post-Newtonian expansions at dierent orders. The alternatives are encouraging and lead to quasi-circular orbits and show gravitational radiation from the onset, as well as a reduction of spurious radiation. Deficiencies compared to punctures include more eccentricity during inspiral and larger constraint violations, since the alternative data sets only approximate solutions of Einstein's equations.We describe a method to solve the constraint equations and apply it to the post-Newtonian expansion in ADMTT gauge. In this method the constraints are elliptic equations, and are discretized using a pseudospectral method implemented within the SGRID code. These discretized equations are then solved with a Newton-Raphson method. The linearized equations needed for the linear step in the Newton-Raphson method are solved with the Generalized Minimal Residual Method (GMRES) using a block-diagonal preconditioner. The resulting initial data are then transferred into the BAM evolution code. We now no longer observe the mass loss that was seen in the unsolved data, and also show smaller constraint violations that are comparable to puncture initial data.
Deciphering Life and Disease at the Molecular Level and a Study of RNA Damage
Zhongwei Li (FAU), Sep 20
I would like to discuss the evolution of molecular research on basic science and diseases, followed by a presentation of a study my research has been focusing on
Introduction to Two Photon Microscopy
Gerardo Estrada (FAU), Oct 18
The entire point of this presentation is to elucidate about the different physical aspects that are important in Two Photon Microscopy. Topics like two photon effects, two photon dyes, pulse lasers and others will be introduced. At the end I will provide some results from my research.
Controlled Heterogeneous Nucleation in Complex Systems
Elsad Allahyarov (Case Western Reserve University), Oct 25
I will talk about our recent results on the nucleation process in soft matter systems using experiments, simulations and theory on colloidal suspensions. In systems with short-range interaction we discovered and investigated a multi-stage process during which an added particle exhibits two different qualities. Initially, crystallization starts on the curved surface of the added large particle. Due to the increasing elastic stress, the crystallite eventually detaches from the seed, from which it is then separated by a liquid. After the detachment, the relaxed crystallite continues to grow in the bulk, but crystallization ceases before reaching the added particle, which now acts as impurity. In overcooled systems with long-range interaction we analyzed the influence of the mismatch between the template and bulk densities on the crystal structures of resulting clusters. We showed that in some particular mismatch cases the template induced nucleation process can result in the development of wrong crystal structures. Questions about the generation of latent heat and associated with it standing waves at the liquid-solid interface are addressed.
Electrostatics in Soft Matter
Andy Lau (FAU), Nov 15
The standard approach to charged systems in soft condensed matter is the mean-field Poisson-Boltzmann (PB) theory. It provides a good approximation to weakly-charged systems. However, fluctuation and correlation effects may sometimes drastically alter its predictions for highly-charged systems. In this colloquium, we discuss some manifestations of these effects in problems containing highly-charged planar surfaces. Specifically, these include counterion-mediated attractions and charge inversions.
What big stars can tell us about tiny Particles: Astrophysics meets Particle Physics
Maurizio Giannotti (Barry University), Nov 22
Stars can be excellent laboratories to study the properties of elementary particles and fundamental interactions. They provide an environment to study new physics not reproducible on earth and often complement earth-based detection methods. I will discuss some of the recent developments in this field and, in particular, a new bound on the axion, an elusive hypothetical particle which has escaped detection for over 3 decades.