Computations in Science Seminars
Mar
11
Wed 12:15
Norbert Scherer, University of Chicago
e-mail:
Host: Leo Kadanoff ()
Organizer: Sayantan Majumdar ()
The Nature of Optical Matter

In contrast to conventional matter, which is made up of chemically bonded constituents (e.g., atoms, molecules, etc.), "optical matter" is bound by light. This form of matter exists in a range of contexts - from optically arranged atomic lattices to close-packed colloidal assemblies to self-organizing arrays of nanoparticles. This talk will focus on the last category, wherein the interactions are created by the electrodynamic interactions amongst the constituent nanoparticles. This is in contrast to well-known methods for creating a user-defined optical lattices or collection of optical tweezers. The primary interactions in nanoparticle-based optical matter are dipolar - where the small metal nanoparticles are well described as point dipoles in the Raleigh limit. They are not near-field but rather originate from the typically neglected intermediate-scale term in the Green's function description of dipolar interactions. As our studies are conducted in liquid environments at room temperature, the relevant energy scale is kT; in fact, attractive and repulsive inter-particle interactions 10-fold greater can be achieved. We use minimally shaped, focused optical beams in which the particles create their long range interactions (essentially an interference effect of mutually scattered light). Therefore, arrays of optically interacting particles represent a many-body problem that requires self-consistent numerical methods to solve Maxwell's equations to model forces and interactions. User defined optical gradient forces and phase gradient forces will be demonstrated as ways to manipulate and control the shape and material properties of particle arrays. These properties include directional stress-strain relationships and yield stress that can result in structural transformations in finite size clusters of nanoparticle-based optical matter. Well defined optical matter arrays also allow exploring the behavior of driven non-equilibrium systems, including elucidating explicit dynamics (particle trajectories) in driven Kramers barrier crossing processes and examining the role of noise (from driving) to create what appear to be hyperuniform states.

Mar
18
Wed 12:15
Jonathon Simon, University of Chicago
e-mail:
Host: Leo Kadanoff ()
Organizer: Kim Weirich ()
Topological Photonics with Twisted Resonators and Braided Circuits

I will present recent work conducted in my group realizing topological phases of photons. Beginning with a spin-hall meta-material for RF photons in coupled resonators, I will proceed to a description of recent progress engineering Landau levels for photons in non-planar (twisted) optical resonators, and mediating strong interactions between harmonically confined, massive photons using resonator Rydberg-EIT. This work holds short-term promise for dissipative production of photonic Laughlin states, and long-term potential as a route to controlled studies of anyons.

Mar
25
Wed 12:15
Daniel Koll, University of Chicago
e-mail:
Host: Wendy Zhang ()
Using dimensional analysis, scaling theory, and computation to understand the atmospheric circulations of exoplanets.

Although current observations of exoplanets focus on large, hot and gaseous planets, it is very likely that we will be able to study the atmosphere of a rocky planet around a nearby star within the next 5 years. The extent to which such a planet and its atmosphere might resemble the planets in our own solar system is still unknown. In this talk I will give an overview of the rapidly-evolving observations, before focusing on how dimensional analysis and scaling arguments can help us understand them. Starting with toy models of an atmosphere and then adding complexity, I will review basic scaling estimates for planetary temperature structures and wind speeds. In many cases these arguments can capture broad features of atmospheric circulations and more complex numerical models. I will then discuss how such theories can be applied to observations. In particular, near-future observations might be able to measure the day-night temperature contrast of exoplanets, which for many planets will be largely set by the atmospheric energy transport. I will show how dimensional analysis coupled with computation allows us to interpret these observations in new ways, and might even be used to infer the surface pressure of terrestrial exoplanets. Such constraints will be important for understanding the atmospheric evolution of terrestrial exoplanets, and for characterizing the surface conditions of potentially habitable planets.

Apr
1
Wed 12:15
Andrea Bertozzi, UCLA
e-mail:
Host: Leo Kadanoff ()
Apr
8
Wed 12:15
Emmanuel Villermaux, Institut Universitaire de France
e-mail:
Host: William Irvine ()
Explosive Fragmentation

The forced radial expansion of a spherical liquid shell by an exothermic chemical reaction is a prototypical configuration for the explosion of cohesive materials in three dimensions. The shell is formed by the capillary pinch off of a thin liquid annular jet surrounding a jet of reactive gaseous mixture at ambient pressure. The encapsulated gas in the resulting liquid bubble is a mixture of hydrogen and oxygen in controlled relative proportions, which is ignited by a laser plasma aimed at the center of the bubble. The strongly exothermic combustion of the mixture induces the expansion of the hot burnt gas, pushing the shell radially outwards in a violently accelerated motion. That motion triggers the instability of the shell, developing thickness modulations ultimately piercing it in a number of holes. The capillary retraction of the holes concentrates the liquid constitutive of the shell into a web of ligaments, whose breakup leads to stable drops. We offer a comprehensive description of the overall process, from the kinematics of the shell initial expansion, to the final drops size distribution as a function of the composition of the gas mixture, and the initial shell radius and thickness of the bubble. This problem, in which the fragments distribution is the result of a competition between deformation, breakup and cohesion, is relevant to a collection of phenomena spanning over a broad range of length scales, among which are: Exploding blood cells in the human body, spore dispersal from plants, boiling droplets, underwater explosions, magma eruption in volcanoes, up to the torn patterns of supernovae in the Universe.

Apr
15
Wed 12:15
Michael Brenner, Harvard
e-mail:
Host: Leo Kadanoff ()
Apr
22
Wed 12:15
Joseph Vallino, Marine Biological Labortory
e-mail:
Host: Leo Kadanoff ()
Apr
29
Wed 12:15
Michael Rubenstein, Harvard
e-mail:
Host: Leo Kadanoff ()
May
6
Wed 12:15
Tim Sanchez, Harvard
e-mail:
Host: Leo Kadanoff ()
May
13
Wed 12:15
Luis Bettencourt, Santa Fe Institute
e-mail:
Host: Daniel Holz ()
May
20
Wed 12:15
Andrew Ferguson, University of Illinois at Urbana-Champaign
e-mail:
Host: Leo Kadanoff ()
May
27
Wed 12:15
Matthew Pinson, University of Chicago
e-mail:
Host: Leo Kadanoff ()
Jun
3
Wed 12:15
Alisa Bokulich, Boston University
e-mail:
Host: Leo Kadanoff ()
Jun
10
Wed 12:15
OPEN
Jun
17
Wed 12:15
OPEN
Jun
24
Wed 12:15
OPEN
Jul
1
Wed 12:15
OPEN
Jul
8
Wed 12:15
OPEN
Jul
15
Wed 12:15
OPEN
Jul
22
Wed 12:15
OPEN
Jul
29
Wed 12:15
OPEN
Aug
5
Wed 12:15
OPEN
Aug
12
Wed 12:15
OPEN
Aug
19
Wed 12:15
OPEN
Aug
26
Wed 12:15
OPEN
Sep
2
Wed 12:15
OPEN
Sep
9
Wed 12:15
OPEN
Sep
16
Wed 12:15
OPEN
Sep
23
Wed 12:15
OPEN
Sep
30
Wed 12:15
OPEN
Oct
7
Wed 12:15
OPEN
Oct
14
Wed 12:15
OPEN
Oct
21
Wed 12:15
David Schuster, University of Chicago
Oct
28
Wed 12:15
OPEN
Nov
4
Wed 12:15
OPEN
Nov
18
Wed 12:15
OPEN
Dec
2
Wed 12:15
OPEN
Dec
9
Wed 12:15
OPEN
Dec
16
Wed 12:15
OPEN