Physics Colloquium – Roshanak Etemadpour

KIRC 1150 3135 N. Maryland Ave., Milwaukee, WI, United States

Roshanak Etemadpour, Ph. D. candidate, Department of Physics, University of Wisconsin-Milwaukee

The title and abstract for this talk will be posted when made available.

Physics Colloquium – Francis Halzen

KIRC 1150 3135 N. Maryland Ave., Milwaukee, WI, United States

IceCube: Opening a Neutrino Window on the Universe from the South Pole
Professor Francis Halzen, Professor and Director of IceCube, Department of Physics, University of Wisconsin-Madison

Below the geographic South Pole, the IceCube project has transformed one cubic kilometer of natural Antarctic ice into a neutrino detector. IceCube detects more than 100,000 neutrinos per year in the GeV to 10 PeV energy range. From those, we have isolated a flux of high-energy neutrinos originating beyond our Galaxy, with an energy flux that is comparable to that of the extragalactic high-energy photon flux observed by the NASA Fermi satellite. With a decade of data, we have identified their first sources, which point to the obscured dense cores associated with the supermassive black holes of some active galaxies as the origin of high-energy neutrinos (and cosmic rays!).

Physics Colloquium – Helvi Witek

KIRC 1150 3135 N. Maryland Ave., Milwaukee, WI, United States

CSI Gravity: Investigating Mysteries of Fundamental Physics with Black Holes

Dr. Helvi Witek, Asst. Professor, Dept. of Physics, UIUC
Black holes are among the most exciting predictions of Einstein's theory of general relativity, composed of the fabric of spacetime itself. Observations of black holes offer unique access to extreme gravity, and they enable us to investigate long-standing puzzles in fundamental physics ranging from dark matter to the very nature of gravity itself.

Physics Colloquium – Sarah Vigeland

KIRC 1150 3135 N. Maryland Ave., Milwaukee, WI, United States

Searching for a Gravitational Wave Background with Pulsar Timing Arrays

Sarah Vigeland, Asst. Professor, Dept. of Physics, UW-Milwaukee
Pulsar timing arrays use observations of millisecond pulsars to detect nanohertz gravitational waves. The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) Collaboration has recently released their 15-year data set containing observations of 68 millisecond pulsars. These data contain evidence for Hellings-Downs correlations, which are characteristic of a gravitational wave background.

Physics Colloquium – Alan Wiseman

Lapham 162 3209 N. Maryland Ave., Milwaukee

The Self-force on Static and Dynamic Charges in Schwarzschild Spacetime Using the Method of Images
Alan Wiseman, Assoc. Professor, Dept. of Physics, UW-Milwaukee
One of the most basic examples of a self-force phenomenon (sometimes called the radiation reaction force) is that of a small, charged particle near a large spherical mass such as a Schwarzschild black hole. If the particle is held stationary, there are novel electrostatic forces on the particle. If the particle is orbiting the mass, the fields created by the particle back-react on the particle and cause it to depart from its otherwise free-fall motion. There are many ways to solve for the forces and motion in these circumstances, but past solutions have involved considerable technical machinery, and the results are messy and "non-intuitive".

Physics Colloquium – Gabor Csathy

KIRC 1150 3135 N. Maryland Ave., Milwaukee, WI, United States

Professor Gabor Csathy, Department of Physics and Astronomy, Purdue University

Emergent Particles and Topology in Flat Landau Bands

Electronic systems with flat energy bands support a variety of topological phases of current interest. The two-dimensional electron gas in the fractional quantum Hall regime is such a system. Ground states of this system found an elegant description in terms of emergent particles called composite fermions.

Physics Colloquium – Marcus Noack

KIRC 1150 3135 N. Maryland Ave., Milwaukee, WI, United States

Dr. Marcus Noack, Research Scientist, Lawrence Berkeley National Lab
Next-Generation Gaussian Processes for Function Approximation, Uncertainty Quantification, and Decision-Making
Gaussian processes (GPs) and Gaussian-related stochastic processes are powerful tools for function approximation, uncertainty quantification, global optimization, and autonomous data acquisition due to their robustness, analytical tractability, and natural inclusion of Bayesian uncertainty estimates. Even so, Gaussian processes are often criticized for poor approximation performance and neck-breaking computational costs in real-life applications. The reason for this gap, however, is not the methodology itself but rather a user-caused lack of flexibility and domain awareness of the underlying prior probability distribution.

Physics Colloquium – Joel Nowitzke

KIRC 1150 3135 N. Maryland Ave., Milwaukee, WI, United States

Joel Nowitzke, PhD Candidate, UW-Milwaukee
Modeling and Measurements of Network Formation and Viscoelastic Behavior of Folded Protein-Based Hydrogels
Proteins are vital for various daily functions and are even used in creating biocompatible materials through chemical crosslinking. However, predicting the mechanical properties of these materials is challenging due to the random orientation of constituent molecules within the network. Bridging the gap between nanoscopic and macroscopic scales is essential for formulating predictable biomaterials.

Physics Colloquium – Rob Pisarski

KIRC 1150 3135 N. Maryland Ave., Milwaukee, WI, United States

Rob Pisarski, Distinguished Scientist, Department of Physics, Brookhaven National Laboratory

The Ugly Duckling and the Swan: The Quark-Gluon Plasma and Heavy Ion Collision

I give a pedagogical and historical overview of the search for the Quark-Gluon plasma (QGP) in the collisions of heavy ions. I begin with a brief review of why we expect a QGP to be formed at high temperature. In this, numerical simulations in lattice Quantum ChromoDynamics (QCD) form the bedrock of the field. In particular, they demonstrate the relationship between deconfinement and the restoration of chiral symmetry.

Physics Colloquium – Segev BenZvi

KIRC 1150 3135 N. Maryland Ave., Milwaukee, WI, United States

Segev BenZvi, Assoc. Professor, Department of Physics, University of Rochester

Measuring Cosmic Expansion with the Dark Energy Spectroscopic Instrument

Since the first observations of the accelerating expansion of the universe at the end of the 1990s, astronomers and physicists have struggled to understand dark energy, a mysterious repulsive force that drives the acceleration. A number of models of dark energy exist. The simplest (the cosmological constant), assumes dark energy is non-interacting and is the same everywhere in space and time. Different models predict subtely different features in the large-scale structure of the universe. We are now entering an era of new photometric and spectroscopic surveys which can discriminate different models of dark energy with unprecedented precision.