Events on Friday, October 10th, 2025
- Theory Seminar (High Energy/Cosmology)
- Quantum Gravity Fluctuations in Causal Diamonds and Cosmology
- Time: 11:00 am - 12:30 pm
- Place: Chamberlin 5280
- Speaker: Lars Aalsma, Minnesota U., Duluth
- Abstract: Given that the Planck length is 10^{-35} meters, directly measuring quantum gravity effects does not seem feasible. For this reason, finding physical systems where quantum fluctuations are enhanced is crucial to put theoretical ideas about quantum gravity to the test. Work by Verlinde and Zurek in 2019 has suggested that an enhancement of geometrical fluctuations takes place in a ‘causal diamond’: the causally accessible region to an observer in a finite time interval. This has been dubbed the ‘VZ-effect’. If correct, this leads to a quantum gravitational background noise that can be measured by future dedicated interferometry experiments. In this talk, I will explain the status of this proposal and highlight some of its controversial aspects. To address these controversies, I will show that the fluctuations proposed by VZ have a natural interpretation in inflationary cosmology. This clarifies the assumptions that need to be satisfied for the ‘VZ-effect' to be observable.
- Host: Gary Shiu
- Physics Department Colloquium
- Superfluid ³He: Science and Serendipity
- Time: 3:30 pm - 4:30 pm
- Place: Chamberlin 2241
- Speaker: Bill Halperin, Northwestern University
- Abstract: The remarkable discovery of superfluid ³He has paved the way for the modern era of quantum condensed states of matter. I recount this development from a personal perspective highlighting the role of serendipity and the interplay between experiment and prediction. There are fits and starts, beautiful physics, a road that continues with rich promise and the occasional disappointment. Yet superfluid ³He is inspirational for unconventional superconductivity, possible condensates of dense quark matter, cores of neutron stars, and proposed sensors of dark matter.
- Host: Alex Levchenko