Pattern Forming Swarms and the Physics of Mixed Reality

Date: October 27, 2017
Time: 3:00 pm

Location: Planetary Hall Room 126

Featured Speaker:
Ira Schwartz
Naval Research Laboratory, Washington DC

Abstract:
With the availability of ever more cheap and powerful computing, interest in the use of augmented and mixed-reality experiments has grown considerably in the engineering and physical sciences. Broadly speaking, these experiments consist of a simulated, or virtual model coupled directly to a physical experiment. Within the physical experiment, it is typical to find a good deal of uncertainty and noise since it is connected to the real world, and thus subjected to random perturbations. In contrast, the virtual part of the coupled system represents a somewhat idealized version of reality in which noise can be eliminated entirely, or at least well characterized. Thus, mixed-reality systems have very skewed sources of uncertainty spread through the entire system.

In this talk, we consider the pattern formation of delay – coupled swarms theoretically and experimentally to illustrate the idea of mixed-reality. Motivated by physical experiments, we then consider a generic model of a mixed-reality system, and show how noise in the physical part of the system can influence the virtual dynamics through a large fluctuation, even when there is no noise in the virtual components. The virtual large …

The Cause of Earth’s Magenetic Field

Date: October 17, 2017
Time: 11:00 am

Location: Planetary Hall Room 242

Featured Speaker:
John Shebalin
George Mason University, Department of Physics and Astronomy, Space Weather Lab

Abstract:
The Earth’s quasi-steady dipole magnetic field may be due to magnetohydrodynamic turbulence within the outer core. Here, the theoretical and computational results that lead to this hypothesis will be discussed, and new numerical results will be presented.

The New Horizons Mission to Pluto: A Recap of Science Results, and a Look Forward to the Encounter with 2014MU69

Date: October 13, 2017
Time: 3:00 pm

Location: Planetary Hall Room 126

Featured Speaker:
Michael Summers
George Mason University, Department of Physics & Astronomy

Abstract:
The New Horizons spacecraft made its closest approach to the Pluto/Charon double planet system on July 14, 2015. The observations, and especially the images of Pluto and Charon returned by the spacecraft were astonishing, and provided many surprises. Those surprises included a gigantic glacier, presumably made of nitrogen, methane, and possibly other ices, on Pluto’s equator that buffers Pluto’s atmosphere. Another was the apparently “fresh” nature of the surfaces of both Pluto and Charon, implying geological “young” ages for these objects. And yet another surprise was the global system of haze layers for which we still lack a convincing explanation. The information from the New Horizons encounter has taught us much, yet it has opened up completely new questions about how planets form and evolve. In this talk I will give a recap of the major science results from the New Horizons mission as well as an overview of the key remaining questions. I will also discuss what we can expect as the New Horizons spacecraft travels onward to its next flyby of Kuiper …

Seeing Double: Scientists Find Elusive Giant Black Hole Pairs

This graphic shows two of five new pairs of supermassive black holes recently identified by astronomers using a combination of data from NASA’s Chandra X-ray Observatory, the Wide-Field Infrared Sky Explorer Survey (WISE), and the ground-based Large Binocular Telescope in Arizona. This discovery could help astronomers better understand how giant black holes grow and how they may produce the strongest gravitational wave signals in the Universe

Astronomers have identified a bumper crop of dual supermassive black holes in the centers of galaxies. This discovery could help astronomers better understand how giant black holes grow and how they may produce the strongest gravitational wave signals in the Universe.

The new evidence reveals five pairs of supermassive black holes, each containing millions of times the mass of the Sun. These black hole couples formed when two galaxies collided and merged with each other, forcing their supermassive black holes close together.

The black hole pairs were uncovered by combining data from a suite of different observatories including NASA’s Chandra X-ray Observatory, the Wide-Field Infrared Sky Explorer Survey (WISE), and the ground-based Large Binocular Telescope in Arizona.

“Astronomers find single supermassive black holes all over the universe,” said Shobita Satyapal, from George Mason University in Fairfax, …

Colloquium: Optimal Control of Networks: Energy Scaling and Open Challenges

Date: October 6, 2017
Time: 3:00 pm

Location: Planetary Hall Room 126

Featured Speaker:
Francesco Sorrentino
University of New Mexico, Department of Mechanical Engineering

Abstract:
Recent years have witnessed increased interest from the scientific community regarding the control of complex dynamical networks. Some common types of networks examined throughout the literature are power grids, communication networks, gene regulatory networks, neuronal systems, food webs, and social systems. Optimal control studies strategies to control a system that minimize a cost function, for example the energy that is required by the control action.

We show that by controlling the states of a subset of the nodes of a network, rather than the state of every node, the required energy to control a portion of the network can be reduced substantially. The energy requirements exponentially decay with the number of target nodes, suggesting that large networks can be controlled by a relatively small number of inputs, as long as the target set is appropriately sized.

An important observation is that the minimum energy solution of the control problem for a linear system produces a control trajectory that is nonlocal. However, when the network dynamics is linearized, the linearization is only valid in a local region of the state space and hence the …

Colloquium: The Dynamo Problem, or: Where does the Earth’s Magnetic Field Come From?

Date: September 29, 2017
Time: 3:00 pm

Location: Planetary Hall Room 126

Featured Speaker:
John Shebalin
Space Weather Lab, GMU

Abstract:
The origin of the Earth’s magnetic field has been a puzzle for millennia, and only in the last hundred years has an answer emerged, one that is still being refined. When it was realized that the geomagnetic field had to be produced dynamically within a liquid iron layer deep within the Earth, the “dynamo problem” arose. The essential resolution of this problem came through computational and theoretical research in magnetohydrodynamics (MHD). The primary challenge in this research was, and still is, the mathematical modelling and numerical simulation of the nonlinear dynamics of a turbulent, electrically conducting fluid. I will review historical progress in understanding the Earth’s magnetic field, as well present more recent theoretical and numerical results. Although the focus here is a geophysical one, these results may also be relevant for understanding the magnetic fields of other planets, as well as of the sun and other stars.

Refreshments will be served.

Colloquium: Apollonian Fractal — Numbers, Geometry, and Physics

Date: September 22, 2017
Time: 3:00 pm

Location: Planetary Hall Room 126

Featured Speaker:
Jerzy Kocik
Southern Illinois University, Department of Mathematics

Abstract:
Not only is the Apollonian configuration of circles an aesthetically noteworthy fractal but it also possesses a surprisingly rich mathematical structure. In particular, it conceals the main ingredients of modern physics, like Minkowski space-time, a model of spin, analogies of the quantum Aharonov-Bohm-like phenomena, and more. We shall gently explore these results, uncovering facts that should be found interesting and inspiring to students, researchers, and enthusiasts of geometry and physics.

Refreshments will be served.

Colloquium: Mathematics and Climate

Date: September 8, 2017
Time: 3:00 pm

Location: Planetary Hall Room 126

Featured Speaker:
Hans G. Kaper
Georgetown University and Mathematics and Climate Research Network

Abstract:
Mathematical models and statistical arguments play a central role in the assessment of the changes that are observed in Earth’s climate system. While much of the discussion of climate change is focused on large-scale computational models, the theory of dynamical systems provides the language to distinguish natural variability from change. In this talk I will discuss some problems of current interest in climate science and indicate how, as mathematicians, we can find inspiration for new applications.

Refreshments will be served.

Twitter Q&A with Dr. Geller on the solar eclipse

Tuesday, August 15, Twitter Q&A with Associate Professor & Observatory Director, Dr. Harold Geller. Follow @GeorgeMasonNews on Twitter for the Q&A starting at 12pm!

Our #solareclipse17 Q&A is Aug. 15 at 12p! Tweet questions to @GeorgeMasonNews using #VaEclipse or send them in advance to jroger20@gmu.edu pic.twitter.com/7c27QjyhzH

— George Mason News (@GeorgeMasonNews) August 14, 2017

Spring 2017 Semester Colloquia Schedule

Colloquia for the Spring 2017 Semester will take place from 3:00 to 4:15 pm in Exploratory Hall, Room L003, unless otherwise noted.

Refreshments will be served.

Date
Speaker
Affiliation
Title and Abstract

Jan. 27
Joel Green
Space Telescope Science Institute
The Fiery Seeds of Planet Formation

Feb. 3
Joe Pesce
NSF
Physics and Astronomy at the National Science Foundation

Feb. 17
Bob Bartolo
Former IEEE Congressional Fellow
Solving Today’s Complex Environmental Challenges: A Physicist’s Perspective as a Recovering Congressional Fellow

Mar. 3
Craig Dukes
University of Virginia
Probing the Frontiers of Physics Using Rare Particle Decays

Mar. 10
Normand Mousseau
Départment de physique, Université de Montréal
Understanding and controlling materials’ properties : Why time is of the essence

Mar. 31
Canceled

Apr. 7
Yi Li
JHU
TBD

Apr. 21
Miguel Sanjuan
Universidad Rey Juan Carlos
Basin Entropy: A new tool to explore uncertainty in dynamical systems

Apr. 28
Annemarie Exarhos
University of Pennsylvania
Optical Signatures of Single-Photon Sources in Hexagonal Boron Nitride

May 5
Jay Deep Sau

TBD

Fall 2016 Semester Colloquia Schedule

Colloquia for the Fall 2016 Semester will take place from 3:00 to 4:15 pm in Exploratory Hall, Room L111, unless otherwise noted.

Refreshments will be served.

Date
Speaker
Affiliation
Title and Abstract

Sept. 23
Pauli Kehayias
Harvard
Magnetic Microscopy and NMR with Nitrogen-Vacancy Defect Centers in Diamond

Oct. 7
Alina Bruma
NIST
Spontaneous ordering at nanoscale level : superlattice formation in transition metal nanocubes

Oct. 20
Please note different location
Markita del Carpio Landry
UC Berkeley
Imaging Neurochemistry with Synthetic Fluorescent Nanosensors

Nov. 4
Katrina Groth
Sandia National Lab
TBD

Nov. 18
Sonya Bahar
University of Missouri at St. Louis
Phase Transitions in Evolutionary Dynamics

Dec. 2
Kent Thurber
NIH
Dynamic Nuclear Polarization (DNP) for Solid-state NMR of Biological Samples