Weekly Colloquium

Most weeks during the semester, we host a scholar for a one-day visit. The visit culminates with a public talk on a topic of contemporary physics or astronomy. Students are welcome to these talks, and seniors are required to attend at least nine over the course of a year. Near the end of each semester, honors thesis students give public lectures on their work.  We gather before the talks for tea, coffee, and cookies at 3:45, Ground Lobby of Science Center followed by the talk at 4:00 pm in A011.

Our Astronomy program is part of the Five College Astronomy Department, which hosts its own colloquium series Thursdays at 3:45 pm at UMass in LGRT 1033. 

  • If you would like to be mailed seminar announcements, please send an email to physics@amherst.edu.
  • Contact colloquium organizer Alice Simmoneau (asimmoneau@amherst.edu) with any questions about colloquia.

February 2020

Tue, Feb 4, 2020

Protik K. Majumder, Williams College: "Heavy Metals, Cheap Lasers and Precision Measurements of Atomic Structure"

With important contributions from many Williams undergraduates over recent years, we have completed a series of high-precision spectroscopic measurements in Group III and IV atoms such as thallium, indium and lead. These results test state-of-the art theoretical models of these complicated atoms and guide further refinement. I will discuss some recent results including a new precision measurement of a “forbidden” transition in lead which makes use of a laser polarimetry technique capable of microradian optical rotation resolution. Improved models of these heavy atoms aid in the bigger goals of testing the Standard Model (and beyond) with table-top atomic and laser physics experiments.

Tue, Feb 11, 2020

David Hall ’91, Amherst College: “Tying Knots in a Quantum Fluid”

Knots are familiar entities that appear at a captivating nexus of art, technology, mathematics and science. They have recently attracted significant experimental interest in contexts ranging from knotted DNA and nanostructures to nontrivial vortex knots in classical fluids. In this talk, I will discuss the first controlled
experimental creation and detection of knot solitons, which are particle-like topological excitations possessing a knotted field character. The superfluid medium within which they exist is a Bose-Einstein condensate with a temperature some tens of billionths of a degree above absolute zero. In addition to enabling future experimental studies of their properties and dynamics, these knot solitons provide a striking demonstration of the celebrated Hopf fibration, which mathematically tie together many seemingly unrelated physical phenomena.

Tue, Feb 18, 2020

Sanam Nader-Esfahani, Amherst College: “Literature and the Eye in the Age of Kepler”

“I shall describe the means of vision, which no one at all to my knowledge has yet examined and understood in such detail. I therefore beg the mathematicians to consider these carefully, so that thereby at last there might exist in philosophy something certain concerning this most noble function.” It is with these words in his Optical Part of Astronomy (1604) that the German mathematician Johannes Kepler credits himself with inaugurating a new chapter in the history of vision. Kepler does indeed fulfill his promise by advancing knowledge about the eye, vision and the use of lenses in the correction of vision. His conclusions, however, bring anything but certainty on a philosophical level, especially with regard to the relationship between an object and its image. Reading Kepler in dialogue with a selection of nonscientific texts, this presentation experiments with the affinities between Kepler’s scientific findings and literature as a form of knowledge and representation in the 17th century.

Tue, Feb 25, 2020

Chris Faesi, UMass: “The Forest AND the Trees: Bridging the Multi-Scale Physics of Star Formation”

The conversion of interstellar gas into stars provides the energy, momentum and chemical enrichment that help drive the evolution of galaxies across cosmic time. Observational limitations have previously made it difficult to obtain a comprehensive understanding of the star formation process (and its role on environment) due to the large dynamic range in scales over which it is relevant. However, pioneering new observational facilities are now moving the field from case studies to big data, enabling measurements across statistically significant samples of galaxies at very high resolution. This allows us for the first time to directly investigate how the small-scale (< 100 pc) physics of star formation couples to large-scale (1-10 kpc) galactic dynamics and environment.

In this presentation, I will highlight recent and current progress toward a more complete picture of star formation in the local Universe. I will show how new population synthesis models for young stellar populations can bridge the gap from Milky Way to extragalactic star formation studies. I will also present the results of the first molecular cloud-scale study of molecular clouds beyond the Local Group of galaxies. Finally, I will review some first results from two large observational campaigns through which we are tracking molecular gas and young stars at the cloud scale across dozens of nearby galaxies. This includes the systematic investigation of important physical quantities including gas conversion efficiency, molecular cloud densities and dynamics, and star formation timescales across multiple galactic environments.