Physics

Seminars in Spring 2016

All seminars are held at 4:10 PM in Physics 123, unless otherwise noted.
Refreshments will be served at 4:00 PM.

Jan 27

Professor John Essick, Reed College
Changing Quantum-Dot Optical Properties with the Twist of a Knob

The optical absorption and photoluminescence properties of CdSe and Mn-doped ZnSe quantum dots will be reviewed. When incorporated as the active layer in an electrochemical cell, it will be shown that the photoluminescence of these materials can be increased (“electrobrightening”) or decreased (“Auger quenching”) by filling selected electronic states through the application of an appropriate bias. Finally, results on a mixed CdSe/Mn:ZnSe sample whose photoluminescence can be tuned from green to orange with applied bias will be presented and attempts to produce a high-field electroluminescent device with a quantum dot active layer will be discussed.

Feb 3

Neil Cornish, Montana State University
The Dawn of Gravitational Wave Astronomy

A century has past since Einstein published his theory of gravity and predicted the existence of gravitational waves.  For the past half century, researchers around the world have attempted to detect these elusive waves with increasingly sensitive instruments across a range of wavelengths. A race of sorts has developed between the kilometer-scale laser interferometers operating in the auditory frequency range, and the galactic-scale pulsar timing arrays operating in the nanoHertz range. While the first direct detection of gravitational waves will be a momentous event, it will not be the end of the story, but rather, the beginning of a new era in astronomy, with the potential to transform our view of the Universe.

Feb 10

Gabriel Barello '12, University of Oregon
New Models of Kinetic Mixing

Dark matter may be just one part of an entire dark sector: many new particles and forces that only weakly interact with “normal” matter. These new forces come with new force mediating particles, the simplest of which is the “dark photon”. An amazing prediction of any theory with a dark photon is that it will spontaneously turn into a photon with some (presumably small) probability, a phenomenon called kinetic mixing.

There has been a lot of interest in dark photons and kinetic mixing during the last decade. Many experiments are currently searching for dark photons, so stay tuned over the next few years as data is released! 

In this talk I will describe kinetic mixing and the current state of dark photon searches. I will then go on to discuss some recent work which predicts a new particle associated with kinetic mixing. This new particle interacts with the weak and electromagnetic forces, and may have already been produced at the LHC!

Feb 17

Brooks Thomas, Colorado College
Renvisioning the Invisible: A New Perspective on the Dark-Matter Puzzle

Overwhelming evidence now suggests that the majority of the matter in our universe consists of some exotic "dark matter" that neither emits nor absorbs light, yet makes its presence felt via its gravitational pull on normal matter.  Over the years, a number of simple and elegant ideas have been advanced to explain the nature and origin of this dark matter.  However, a variety of puzzling experimental results and tantalizing potential signals have recently emerged which are difficult for these simple proposals to explain.  These results have motivated more complicated proposals for what the dark matter might be, and have even given birth to the idea that our universe might contain a whole "dark sector" comprising a variety of different particles with different properties, all hiding in plain sight.  In this talk, I'll review what we do know about dark matter, explain why traditional ideas about dark matter are being called into question, and describe an alternative perspective on the dark-matter puzzle -- one which in some sense represents the most general approach to that puzzle which can possibly be imagined.  This new perspective brings to light a variety of new possibilities for dark matter whose unusual and distinctive experimental consequences are only beginning to be explored.

Feb 24

David Griffiths, Emeritus Professor, Reed College
The Charge Distribution on a Conductor

In electrostatics any excess charge on a conductor goes to the surface.  This is due, of course, to the mutual repulsion of like charges.  But it depends critically on the precise form of Coulomb's law and on the dimensionality of the conductor.  I will discuss some intriguing examples, including the vexed case of a conducting needle.

Mar 2

Max Schlosshauer, University of Portland
Do Not Disturb: How to Measure the Quantum State of a Single System

In quantum mechanics, a physical system is described by its quantum state. Characterizing a system's quantum state is an important experimental task and of great significance to quantum-information processing. However, there's a fundamental problem: Any measurement of a quantum state will alter that state, meaning that we cannot help but disturb what we're trying to observe. In this talk, I will show how one can measure the state of a single quantum system in the least disruptive way possible.

Mar 9

Chris Dimitriou, Nike
Continuum Mechanics and Rheological Constitutive Modeling of Complex Fluids

The terms “complex fluid” and “non-Newtonian fluid” are both typically used to describe materials that exhibit mechanical behavior intermediate to that of elastic solids and viscous liquids. These materials are ubiquitous both in industrial applications and in nature: household products (e.g.  shaving foams, toothpaste, shampoo), polymeric liquids and biological fluids all exhibit different aspects of non-Newtonian behavior. This talk will introduce some of the mathematical and physical principles governing the behavior of complex fluids. We will lay a brief foundation of continuum mechanics, and then discuss some examples of constitutive modeling of complex fluids. Constitutive models are crucial tools used in science and engineering, as they allow the practicing mechanician to model the behavior of a material undergoing deformation. As an example, we focus our constitutive modeling efforts on a particular fluid of significant economic importance: crude oil. Waxy crude oils in particular are known to exhibit several complex features in their rheology, so they serve as a good case study to illustrate the challenges faced in constitutive modeling. Crude oils also serve as the majority component used in the manufacture of synthetic polymers. Since polymeric materials also exhibit non-Newtonian properties, we will end by briefly highlighting some aspects of their rheological behavior.

Mar 16

Evan Peairs, Will Holdhusen, Joseph Joe
Senior Thesis Presentations

Evan Peairs

Designing, Building, and Testing Novel Metallophones

Will Holdhusen

First Quantization of Radiation Reaction

Joseph Joe

Reaction Diffusion Models and Persistent Homology

Mar 30

David Latimer, University of Puget Sound
Some electrodynamics of Majorana fermions (and other neutral particles)

To a good approximation, neutral fundamental particles do not interact electromagnetically. But, through quantum fluctuations, these particles can acquire electric and magnetic dipole moments, as well as an anapole moment.  In this talk, I will explore these interactions, focusing upon one particular type of neutral particle - the Majorana fermion.  By definition, Majorana fermions are their own antiparticles.  As a consequence, their electric and magnetic dipole moments must vanish, leaving the anapole moment as their sole static electromagnetic property. Through scattering processes, we can come to understand the behavior of anapoles, namely their interaction with currents and photons.  Moving beyond the static limit, I will show that dipole moments can be induced in Majorana fermions and discuss some consequences of these higher order interactions.

Apr 6

Sidney Vetens, Indy Liu, Nathan Showell
Senior Thesis Talks

Sidney Vetens

Scalar Tensor Vector Gravity Theory

Indy Liu

Spontaneous Orbital Currents & Degenerate Perturbation

Nathan Showell

The Synchronization of Coupled Oscillators

Apr 13

Timo Delgado, Mike Sommer, Ace Furman, Aaron Cholden-Brown
Senior Thesis Talks

Timo Delgado

Delayed Interactions and Classical Electrodynamics

Mike Sommer

Thermo-Electric Processes in a DC Discharge Plasma

Ace Furman

Electromagnetically Induced Transparency:  The Zeeman Method

Aaron Cholden-Brown

First Quantization Quantum Mechanics on Curved Space-Times

Apr 20

Zuben Scott, Charlie McIntyre, Naomi Gendler
Senior Thesis Talks

Zuben Scott

The Dynamics of Anyons

Charlie McIntyre

Band Structure Calculations in Quantum Dots

Naomi Gendler

Dark Matter Corrections to the Anomalous Magnetic Moment of the Muon

Apr 27

Alex Deich, Colleen Werkheiser, Abrar Abidi, Mateo Ochoa
Senior Thesis Talks

Alex Deich

Particle Dynamics in a Time-Dependent Kerr Spacetime

Colleen Werkheiser

Dynamics of a Time-Delayed Electronic System

Abrar Abidi

Quantifying Cellular Mechanotransduction in Morphogenesis and Metastasis

Mateo Ochoa

Chaos in Oscillatory Hamiltonian Systems