This page lists all of the abstracts for the Fall 2013 colloquium series. For dates and speakers, see Colloquium.

 


 

"The Universe in an Atom: how precision measurements of atomic spins can probe the universe's greatest mysteries," Friday, September 20, 12n, MH 606

Derek Jackson Kimball, California State University - East Bay

Modern cosmology poses deep, unanswered questions about the nature of the universe:

- What is the dark energy that causes the accelerating expansion of the universe?
 
- What is the dark matter whose gravitational influence holds together galaxies and galactic clusters?
 
- What causes the matter-antimatter asymmetry of the universe?
 
We are searching for possible answers to these questions using precise measurements of atomic spins.  Heretofore undiscovered, symmetry-violating interactions could explain dark energy, contribute to dark matter, and generate the matter/antimatter asymmetry of the universe.  Such interactions also produce spin-mass and spin-spin interactions that can be searched for in laboratory experiments in a variety of ways.  We will discuss:
 
(1) recent constraints on such interactions derived from measurements and calculations of electron-mediated nuclear spin coupling in deuterated molecular hydrogen (HD),
 
(2) our ongoing experiment to search for a long-range coupling between rubidium (Rb) nuclear spins and the mass of the Earth, and
 
(3) a new international collaboration, the Global Network of Optical Magnetometers for Exotic physics (GNOME), that will search for correlated transient signals generated by coupling of atomic spins to various exotic particles and fields.

 

"Thermoelectric effects in nanostructures," Friday, October 25, 12n, MH 606

David Sanchez, University of the Balearic Islands, Spain

Modern miniaturization technologies have the potential to dramatically alter the way we actually conceive energy production, transport and distribution. In particular, thermoelectric devices can provide important savings in energy consumption from recovery of waste heat and improved cooling protocols. However, the fundamentals of controlling and manipulating energy flow in nanostructures have not been fully understood yet. We will here discuss the latest developments in thermoelectricity of quantum conductors, emphasizing the role of symmetries, nonlinearities and time-dependent responses.

 

 

"The Evolution of Introductory Physics at the University of Illinois," Friday, November 8, 12n, MH 606

Mats Selen, University of Illinois

 

About 17 years ago we significantly changed the way we taught intro physics at UIUC. The innovation, which is hindsight seems almost trivial, was to define these courses in terms of their content and associated infrastructure rather than in terms of the faculty assigned to teach them. Having our courses rest on a solid departmental foundation rather than on the shoulders of faculty means that faculty have the time and freedom to innovate, making incremental yet significant improvements to these courses over time. In this talk I will discuss this evolution as well as several of the resulting innovations, including prelectures, just in time teaching, peer instruction, and a new approach to labs.
Bio (I forget if you asked for this – if not then please ignore it):
Mats earned B.Sc.('82) and M.Sc.('83) degrees in physics at the University of Guelph, and M.A.('85) and Ph.D.('89) degrees in particle physics at Princeton University. After a four year post-doc at Cornell he joined the faculty at the University of Illinois in 1993 where he has been ever since. After 25 years of studying elementary particles he is shifting his research focus to understanding and improving the way students learn physics. With Illinois colleagues he developed the iclicker classroom response system, the smartPhysics learning framework, and most recently IOLab. On Wednesday mornings he brings science to central Illinois viewers as the WCIA "WhysGuy".

 

 

"Shedding Light on Planet-Disk Interactions," Friday, November 15, 12n, MH 606

 

Dave Tsang, McGill University

 
The new era of exoplanetary discovery has begun to allow a statistical understanding of planetary distributions to inform our knowledge of planet formation and migration. I will discuss a few features of these emerging statistical distributions, and possible mechanisms to produce such features, focussing particularly on disk-planet interactions. I will discuss how wave resonance may affect the distribution of close-in planets, as well as how the "Eccentricity Valley" in the exoplanet distribution around metal-poor stars may be a signature of an eccentricity excitation process related to stellar insolation of giant planets.

 


 

 

"When matter meets antimatter: Experiments with Positronium," Friday, November 22, 12n, MH 606

Adric Jones, UC Riverside

 

Positrons are the simplest and most readily available antimatter particle, and as such have been the subject of significant experimental studies over the past 60 years, leading to applications in medical science, astrophysics and materials science. Ongoing development and improvements in controlling and manipulating large numbers of positrons over the past 20 years has made possible many new experimental investigations, for instance, in the production of antihydrogen at CERN. However, there remains much is that is unknown regarding antimatter, particularly the apparent asymmetry of the ratio of matter to antimatter in the observable universe. 
 
Our research at UCR focuses on Positronium (Ps), a hydrogen-like pseudo-atom comprised of a bound positron and electron pair. Ps is inherently unstable, prone to spontaneous annihilation on nanosecond time scales – resulting in the emission of extremely energetic (511 keV) photons known as gamma rays. Although the short lifetime of Ps makes it a challenging target for experimental investigation, today we can routinely and efficiently produce large numbers of Ps atoms, allowing experimental investigation of many interesting facets of antimatter. 
 
In this talk, I will discuss two such areas in which we have ongoing research on Ps physics at UCR. First, our recent investigations of Rydberg Ps (i.e., Ps in highly-excited states) will be discussed in the context of planned measurements of the gravitational deflection of antimatter. Conventional wisdom predicts that anti-matter and matter should feel an identical gravitational force to matter, however this hypothesis remains to be tested; in fact, the prospect of a repulsive gravitational effect has been the subject of theoretical consideration since the discovery of antimatter in 1932 and is far from a settled question. I will also discuss our efforts towards producing a Bose-Einstein condensate (BEC) of Ps, an exotic quantum state of matter, which requires large densities of Ps cooled to low temperature. Ps would be unique among atomic BECs, as it is expected to exhibit coherent stimulated-annihilation, a process that raises the possibility of some day creating an annihilation gamma-ray laser.
 

 


 

"Producing an Optimal Can," Friday, December 6, 12n, MH 606

 

Michael Campbell

 

Mike was a CSUF double major physics/math class of 1991 who went on to finish his PhD in math at UCLA in 1999 and then on to postdocs at UCI and UC Berkeley.

 
ABSTRACT:
It turns out that the calculus problem of producing an optimal can, i.e. one with minimal surface area and therefore at minimum price, becomes much more interesting when material and storage costs are included. The problem then displays features in“phase transition” phenomena (like a piece of metal magnetizing at low temperature). That is pretty amazing, since it takes some heavy-duty tools to get to the discontinuities that characterize phase transitions, in say, a magnetic system. The can problem has discontinuity built in, so we bypass functional analysis, operator algebras, measure/probability theory, stochastic pde’s and all the other inaccessible tools to cut right to the chase. All that is needed is an understanding of first-semester calculus. As the price for storage increases, the optimal can changes from one with a square profile to one with a rectangular profile. This is essentially “symmetry breaking” in statistical mechanics. This talk will explore this open problem.