Physics Department Colloquium

Abstract: Inflationary cosmology has been widely accepted for decades. Yet there are persistent debates about inflation which raise central questions in philosophy of science. Skeptics have often expressed doubt regarding whether inflation is "testable" or "falsifiable," due to the flexibility of inflationary models. This is an instance of a general question in philosophy of science: to what extent does phenomenological success support the claim that a theory gets the physics right?

Abstract:   Ever since the invention of the laser over 60 years ago, scientists have been striving to create x-ray lasers. In the same way that visible lasers can concentrate light energy far better than a light bulb, a directed beam of x-rays would have many useful applications. The problem was that until recently, ridiculously high powers were needed to make an x-ray laser.

Abstract: Starting from just a sheet of paper, by folding, stacking, crumpling, sometimes tearing, we will explore a diversity of phenomena, from magic tricks and geometry to elasticity and the traditional Japanese art of origami. Much of the lecture consists of table-top demonstrations, which you can try later with friends and family.

So, take a sheet of paper . . .

Abstract:  Inequality is an important and seemingly inevitable aspect of the human society. Various manifestations of inequality can be derived from the concept of entropy in statistical physics. In a stylized model of monetary economy, the probability distribution of money among the agents converges to the exponential Boltzmann-Gibbs law due to entropy maximization.

Abstract: The atomic nucleus emerges from interacting quantum particles called quarks and gluons, but how this happens remains unknown. This might be elucidated with quantum-level "images" of their position, orbital motion, spin alignment, and entanglement. I will describe recent and upcoming experiments at the Thomas Jefferson Laboratory that use a high-intensity, high-energy electron beam to probe a wide range of nuclear targets, from polarized lithium to lead.

Abstract: Superconducting quantum computers, once scaled up, could solve problems intractable to even the largest classical supercomputers, but better superconducting qubits are needed before this can occur. Superconducting qubit coherence is currently limited both by cryogenic low-power dielectric loss and by large temporal fluctuations due to strongly-coupled defects.

Abstract: In classical physics, unbounded (or "up-side-down")
potentials do not allow for a stable ground state. As a consequence,
unbounded potentials have often been dismissed as not viable for
proper unitary quantum theories. Historically, we have learned that
the quantum world often contradicts dearly held beliefs based on
classical physics. By contrast, mathematics has been recognized as a
good guide even when classical intuition fails.  In this talk, I will
use well-developed mathematics to explore physical systems with

Abstract: Highlights from research done on the National Ignition Facility (NIF) laser through the Discovery Science program will be presented. Plasma nuclear reactions relevant to stellar nucleosynthesis and nuclear reactions in high energy astrophysical scenarios are being studied. [1] Equations of state (EOS) at very high pressures (0.1-100 TPa or 1-1000 Mbar) relevant to planetary cores, brown dwarf interiors, and white dwarf envelopes are being measured on NIF, and show that the level of ionization can significantly affect the compressibility of the sample.