Colloquium Fall 1997



September 22

Why Do People Argue About the Screening Factor in Stellar Nuclear Reactions?
Giora Shaviv
Department of Physics and Asher Space Research Institute
Technion, Haifa, Israel


We describe the on-going controversy on the effect that electrostatic screening may have on the nuclear reactions in the Sun. We show why and where many good people were wrong, how NOT to calculate the effect and how the effect should be calculated.

September 29


October 13

Macroscopic Quantum Physics of a Superfluid 3He Weak Link
"Whistle While You Work"

Seamus (J.C.) Davis
Dept. of Physics, University of California, Berkeley


An applied chemical potential difference between two weakly coupled macroscopic quantum systems should generate mass current oscillations between them. In superconductors, where the weak coupling is usually achieved by using a Josephson tunnel junction, this oscillating current is sometimes called the AC Josepson Effect.

I will describe recent experiments, with an array of 100 nm diameter apertures, which have confirmed the existence of these quantum oscillations in superfluid 3He-B. I will also report on the first direct measurement of the current phase-difference relation, I(phi), for a superfluid 3He weak link, along with a number of other phenomena associated with the Josephson effect which have now been observed in 3He. In addition, a newly discovered metastable macroscopic quantum state will be discussed.

This experiment reveals several remarkable phenomena heretofore inaccessible to superconducting Josephson junctions, such as direct observation of quantum oscillations and continuous knowledge of the dynamics of the quantum phase difference. I will also describe how the observation of a sine-like I(phi) relation lays the foundation for the future creation of a superfluid analog of a dc-SQUID.

October 27

Molecular Engineering of Liquid Crystals for Display Applications
Shin-Tson Wu
Hughes Research Laboratory

November 10 Special Location: THH 101

Recent Results from the Mars Pathfinder Mission
Matthew Golombek
Jet Propulsion Laboratory

November 17

A New Method of Signal Processing for Solving Selected Problems in Physics and for Analyzing Experimental Data
Howard Taylor
Depts. of Chemistry and Physics, USC

November 24

Emerging Physics in the Quests for Creating Miniature Exploding Stars and Accelerators
Warren Mori
Depts. of Physics and Electrical Engineering, UCLA

December 1

Spin Dynamics in Low-Dimensional Antiferromagnets
Anders Sandvik
Dept. of Physics, Univ. of Illinois, Urbana-Champaign

December 2 Note Special Day & Location: SLH 102

Non-Equilibrium Quantum Noise in the Fractional Quantum Hall Effect: Listening to Fractional Charge
Claudio Chamon
Dept. of Physics, Univ. of Illinois, Urbana-Champaign


The low energy excitations of fractional quantum Hall (FQH) liquids carry fractional quantum numbers such as charge and statistics. This directly affects the noise spectrum of the FQH current, and, conversely, the noise data provides direct evidence for fractional quantum numbers. In this talk, I will show in detail how the mesurement of shot noise can generally be used as a powerful tool to study the nature of the fractionally charged FQH quasiparticles. Recently, this tool has been succesfully used in the first transport observations of fractional charge by two experimental groups, one in Saclay and the other at the Weizmann Institute. I will also discuss a device which could allow for the direct observation of fractional statistics.

December 8

Harmonic Generation and its Time Control
Bernard Piraux
Département de physique
Catholic University of Louvain, Louvain-la-Nueve, Belgium

  • Department of Physics and Astronomy
  • University of Southern California
  • 825 Bloom Walk
  • ACB 439
  • Los Angeles, CA 90089-0484