Seminars and Colloquia by Series

Series: Other Talks
Tuesday, April 23, 2019 - 15:00 , Location: Skiles 006 , Jaemin Park , Georgia Institute of Technology , jpark776@gatech.edu , Organizer: Jaemin Park

We study whether all stationary solutions of 2D Euler equation must be radially symmetric, if the vorticity is compactly supported or has some decay at infinity. Our main results are the following:

(1) On the one hand, we are able to show that for any non-negative smooth stationary vorticity  that is compactly supported (or has certain decay as |x|->infty), it must be radially symmetric up to a translation. 

(2) On the other hand, if we allow vorticity to change sign, then by applying bifurcation arguments to sign-changing radial patches, we are able to show that there exists a compactly-supported, sign-changing smooth stationary vorticity that is non-radial.

We have also obtained some symmetry results for uniformly-rotating solutions for 2D Euler equation, as well as stationary/rotating solutions for the SQG equation. The symmetry results are mainly obtained by calculus of variations and elliptic equation techniques. This is a joint work with Javier Gomez-Serrano, Jia Shi and Yao Yao. 

Series: Other Talks
Thursday, March 14, 2019 - 15:45 , Location: Skiles Atrium , Chun-Hung Liu , Texas A&M , Organizer: Robin Thomas

Chun-Hung will discuss his employment experience as an ACO alummus. The conversations will take place over coffee.

Series: Other Talks
Saturday, March 9, 2019 - 13:00 , Location: Ebster Recreation Center, Decatur , Evans Harrell, Matt Baker, and GT Club Math, among others , Georgia Tech, Emory, and others , harrell@math.gatech.edu , Organizer: Evans M. Harrell

Mathapalooza! is simultaneously a Julia Robinson Mathematics Festival and an event of the Atlanta Science Festival. There will be puzzles and games, a magic show by Matt Baker, mathematically themed courtroom skits by GT Club Math, a presentation about math and dance by Manuela Manetta, a presentation about math and music by David Borthwick, and a gallery of mathematical art curated by Elisabetta Matsumoto. It is free, and we anticipate engaging hundreds of members of the public in the wonders of mathematics. More info at https://mathematics-in-motion.org/about/Be there or B^2 !

Series: Other Talks
Monday, February 25, 2019 - 14:15 , Location: Skiles 005 , Prasad Tetali , Georgia Tech , Organizer: Greg Blekherman

Georgia Tech is leading the way in Creating the Next in higher education.In this talk I will present (1) My vision for ACO and (2) how my research relates naturally to ACO both where the A,C,O fields are going, and my own specific interests

Series: Other Talks
Wednesday, February 20, 2019 - 12:00 , Location: 005 , Anna Kirkpatrick , Georgia Tech , akirkpatrick3@gatech.edu , Organizer: Cvetelina Hill

Understanding the structure of RNA is a problem of significant interest to biochemists. Thermodynamic energy functions are often key to this pursuit, but it is well-established that these energy functions do not perform well when applied to longer RNA sequences. This work specifically investigates the branching properties of RNA secondary structures, viewed as plane trees. By employing Markov chain Monte Carlo techniques, we sample from the probability distributions determined by these thermodynamic energy functions. We also investigate some of the challenges in employing Markov chain Monte Carlo, in particular the existence of local energy minima in transition graphs. This talk will give background, share preliminary results, and discuss future avenues of investigation.

Series: Other Talks
Thursday, January 31, 2019 - 11:00 , Location: Skiles 005 , Elena Dimitrova , Clemson University , edimit@clemson.edu , Organizer:

This is a SCMB MathBioSys Seminar posted on behalf of Melissa Kemp (GT BME)

Constriction of blood vessels in the extremities due to traumatic injury to halt excessive blood loss or resulting from pathologic occlusion can cause considerable damage to the surrounding tissues with significant morbidity and mortality. Optimal healing of damaged tissue relies on the precise balance of pro-inflammatory and pro-healing processes of innate inflammation. In this talk, we will present a discrete multiscale mathematical model that spans the tissue and intracellular scales, and captures the consequences of targeting various regulatory components. We take advantage of the canalization properties of some of the functions, which is a type of hierarchical clustering of the inputs, and use it as control to steer the system away from a faulty attractor and understand better the regulatory relations that govern the system dynamics.EDIT: CANCELLED

Series: Other Talks
Monday, December 3, 2018 - 15:00 , Location: Howey N110 , Simon Berman , Georgia Tech (Physics) , Organizer: Rafael de la Llave

Thesis defense:
Advisors: Turgay Uzer and Cristel Chandre
Summary:
Thirty years after the demonstration of
the production of high laser harmonics through nonlinear laser-gas
interaction, high harmonic generation (HHG) is being used to probe
molecular dynamics in real time and is realizing its
technological potential as a tabletop source of attosecond pulses in the
XUV to soft X-ray range. Despite experimental progress, theoretical
efforts have been stymied by the excessive computational cost of
first-principles simulations and the difficulty of
systematically deriving reduced models for the non-perturbative,
multiscale interaction of an intense laser pulse with a macroscopic gas
of atoms. In this thesis, we
investigate first-principles reduced models for HHG using
classical mechanics. On the microscopic level, we examine the
recollision process---the laser-driven collision of an ionized electron
with its parent ion---that drives HHG. Using nonlinear dynamics, we
elucidate the indispensable role played by the ionic
potential during recollisions in the strong-field limit. On the
macroscopic level, we show that the intense laser-gas interaction can be
cast as a classical field theory. Borrowing a technique from plasma
physics, we systematically derive a hierarchy of
reduced Hamiltonian models for the self-consistent interaction between
the laser and the atoms during pulse propagation. The reduced models
can accommodate either classical or quantum electron dynamics, and in
both cases, simulations over experimentally-relevant
propagation distances are feasible. We build a classical model based on
these simulations which agrees quantitatively with the quantum model
for the propagation of the dominant components of the laser field.
Subsequently, we use the classical model to trace
the coherent buildup of harmonic radiation to its origin in phase
space. In a simplified geometry, we show that the anomalously high
frequency radiation seen in simulations results from the delicate
interplay between electron trapping and higher energy recollisions
brought on by propagation effects.

Series: Other Talks
Thursday, November 29, 2018 - 09:00 , Location: Skiles, Room 114 , Hassan Attarchi , Georgia Institute of Technology , hattarchi@gatech.edu , Organizer: Hassan Attarchi

Oral Comprehensive Exam

The purpose of this work is approximation of generic Hamiltonian dynamical systems by those with a finite number of islands. In this work, we will consider a Lemon billiard as our Hamiltonian dynamical system apparently with an infinitely many islands. Then, we try to construct a Hamiltonian dynamical system by deforming the boundary of our lemon billiard to have a finite number of islands which are the same or sub-islands of our original system. Moreover, we want to show elsewhere in the phase space of the constructed billiard is a chaotic sea. In this way, we will have a dynamical system which preserves some properties of our lemon billiards while it has much simpler structure.

Series: Other Talks
Tuesday, November 27, 2018 - 13:05 , Location: Skiles Atrium , Cristobal Guzmanal Guzman , Universidad Católica de Chile, Chile , Organizer: Prasad Tetali

Cristobal Guzman will discuss his employment experience as an ACO alummus. The conversations will take place over coffee.

Series: Other Talks
Wednesday, November 14, 2018 - 04:00 , Location: Molecular Science and Engineering Building, Classroom G011 , Christopher Jarzynski , Director, Institute for Physical Science and Technology University of Maryland , Organizer: Rafael de la Llave

Thermodynamics
provides a robust conceptual framework and set
of laws that govern the exchange of energy and matter. Although these
laws were originally articulated for macroscopic objects, it is hard to
deny that nanoscale systems, as well, often exhibit “thermodynamic-like”
behavior. To what extent can the venerable
laws of thermodynamics be scaled down to apply to individual microscopic
systems, and what new features emerge at the nanoscale? I will review
recent progress toward answering these questions, with a focus on the
second law of thermodynamics. I will argue
that the inequalities ordinarily used to express the second law can be
replaced by stronger equalities, known as fluctuation relations, which
relate equilibrium properties to far-from-equilibrium fluctuations. The
discovery and experimental validation of these
relations has stimulated interest in the feedback control of small
systems, the closely related Maxwell demon paradox, and the
interpretation of the thermodynamic arrow of time. These developments
have led to new tools for the analysis of non-equilibrium experiments
and simulations, and they have refined our understanding of
irreversibility and the second law.

Bio
Chris
Jarzynski received an AB degree in physics from Princeton
University in 1987, and a PhD in physics from the University of
California, Berkeley in 1994. After postdoctoral positions at the
University of Washington in Seattle and at Los Alamos National
Laboratory in New Mexico, he became a staff member in the Theoretical
Division at Los Alamos. In 2006, he moved to the University of Maryland,
College Park, where he is now a Distinguished University Professor in
the Department of Chemistry and Biochemistry, with joint appointments in
the Institute for Physical Science and Technology
and the Department of Physics. His research is primarily in the area of
nonequilibrium statistical physics, where he has contributed to an
understanding of how the laws of thermodynamics apply to nanoscale
systems. He has been the recipient of a Fulbright Fellowship,
the 2005 Sackler Prize in the Physical Sciences, and the 2019 Lars
Onsager Prize in Theoretical Statistical Physics. He is a Fellow of the
American Physical Society and the American Academy of Arts and Sciences.

Contact: Professor Jennifer Curtis Email: jennifer.curtis@physics.gatech.edu

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