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Colloquia are Wednesdays at 4:00 p.m. in the JILA Auditorium.Ìý

Coffee, tea and cookies will be available in G1B31 (across from G1B20) from 3:30 - 3:50 p.m.

January 15 — "Toward Quantum Imaging of Nuclei"

• Presenter: Miguel Arratia, University of California, Riverside
• Host: Jamie Nagle
• 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. I will also explain how these studies pave the way for future research at the Electron-Ion Collider (EIC), which will usher in a new era by providing a novel tool: particle jets. To advance EIC jet physics, we are developing next-generation, highly granular calorimeter systems, which can be enhanced with state-of-the-art AI/ML methodologies. I will summarize recent prototype testing conducted at various facilities and discuss plans for further testing and construction in the near future.

January 22 — "Economic inequality from a statistical physics point of view"

• Presenter: Victor Yakovenko, Physics and JQI, University of Maryland, College Park
• Host: Rahul Nandkishore
• 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.ÌýIn 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. Our analysis of empirical data shows that income distributions in the USA and other countries exhibit a two-class structure. The lower class (about 97% of population) is characterized by the "thermal" exponential distribution, whereas the upper class (about 3%) by the "superthermal" Pareto power law.ÌýThe total income share of the upper class expands and contracts dramatically during booms and busts in financial markets.ÌýWe also found that global inequality in energy consumption and CO₂ emissions has been decreasing since 1980 (likely due to the globalization) and converging toward the exponential distribution. The decrease in global inequality stopped recently, when maximal entropy was reached, as we predicted in advance.ÌýAll papers are available at

January 29 — "´¡Ìý·É´Ç°ù±ô»åÌý´Ú°ù´Ç³¾Ìý²¹Ìý²õ³ó±ð±ð³ÙÌý´Ç´ÚÌý±è²¹±è±ð°ù"

• Presenter: Tadashi Tokieda, Stanford University
• Host: Leo Radzihovsky

• 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 . . .

• Bio: Tadashi Tokieda isÌýaÌýprofessor at Stanford University. He grew upÌýasÌýaÌýpainter in Japan, becameÌýaÌýclassical philologist (not to be confused with philosopher) in FranceÌýand, having earnedÌýaÌýPhD in pure mathematicsÌýfromÌýPrinceton, has beenÌýanÌýapplied mathematician in EnglandÌýand the US. He isÌýalsoÌýactive in outreach in the developingÌýworld, especially via theÌýAfrican Institute for Mathematical Sciences (AIMS)Ìýas wellÌýas the YouTube channel Numberphile. Tokieda was invited to deliverÌýaÌýpublic lectureÌýat the 2018 ICMÌýandÌýat the 2022 ICM.

**Special Colloquium** Monday, February 3 — "A view into the flow and fracture of glacier ice"

• Presenter: Joanna Millstein, Colorado School of Mines
• Time: 11:00 a.m.
• Location: JILA Auditorium
• Host: Mike Ritzwoller
• Abstract: Glaciers deform through the driving force of their own weight and display dramatic responses to both external forcing, such as changes in climate, and internal forcing like variations in stress. Determining the response of glaciers and ice sheets to such forcing was, until very recently, limited by sparse observations and data across the cryosphere. The rapid expansion of pertinent and available satellite-based data has created an opportunity to understand the processes contributing to dynamic change through melting and calving, the fracture of icebergs. I leverage the expanding volume of satellite observations to develop and refine models of ice flow and ice fracture through mechanical and statistical frameworks. In this talk, I will discuss a modern reexamination of the constitutive law for glacier ice and new parameterizations for large ice fractures. These observational studies improve higher-order ice sheet models, enabling a more complete view of ice sheet change. This research showcases the power of quantifying and calibrating the processes of ice flow and ice fracture to understand ice sheet stability and to assess future projections of glaciers and ice sheets in a changing climate.

February 5

• Presenter: Margaret Murnane, JILA, University of Colorado, Boulder
• Host:
• Abstract:

February 12

• Presenter: James K. Thompson, JILA, University of Colorado, Boulder
• Host:
• Abstract:

February 19 — "Closing the Loop in Early Universe Cosmology?"

• Presenter: Chris Smeenk, Western University, Canada
• Host: Allan Franklin
• 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? How does one answer a skeptical worry, that the theory "fits the data" because it is flexible? My aim in this talk is reframe this debate, drawing on ideas from George Smith’s historical and philosophical assessment of celestial mechanics. Smith answers the skeptic by looking at the role a theory plays in guiding inquiry. Following Newton, astronomers "closed the loop" by starting with an initial description of motions; using discrepancies with observations to identify sub-dominant physical details; incorporating these details into a more refined description; and then starting the process over again. Through this process astronomers discovered hundreds of new details about the solar system, based on assuming the theory of gravity, that could be checked independently. Considering this case helps to characterize one challenge facing theories of the early universe: our lack of clarity about the underlying physics driving inflation has blocked pursuit of a similar process of iterative refinement. I will close by considering several different responses to this challenge.

February 26

• Presenter: David Keith, University of Chicago
• Host: Eric Cornell
• Abstract:

March 5

• Presenter: Jonathan Lunine, JPL, Caltech
• Host: Mihaly Horanyi
• Abstract:

March 12

• Presenter: Holger Mueller, Berkeley
• Host: Adam Kaufman
• Abstract:

March 19Ìý

• Presenter: Merav Opher, Boston University
• Host: Mihaly Horanyi
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March 26 — No Colloquium, Spring Break

April 2

• Presenter: Martin Formanek, MPIK, Heidelberg, Germany
• Host: Yuan Shi
• Abstract:

April 9

• Presenter: Alireza Marandi, Caltech
• Host: Juliet Gopinath
• Abstract:

April 16

• Presenter: Sébastien Corde, Ecole Polytechnique
• Host: Michael Litos
• Abstract:

April 23

• Presenter: Chunmei Ban, University of Colorado, Boulder
• Host: Joe Berry
• Abstract:

April 30

• Presenter: Steve Girvin, Yale
• Host: Leo Radzihovsky
• Abstract:

For more information about colloquia this semester, contact: Mihaly Horanyi