Physics Department Colloquium

Host: 
Alex Levchenko
Speaker: David Weiss Penn State

 

Available Downloads:

Room and Building: 
2241 Chamberlin Hall
Host: 
Tulika Bose
Speaker: Elizabeth Simmons UCSD

 

Available Downloads:

Room and Building: 
2241 Chamberlin Hall
Host: 
Tulika Bose
Speaker: Steven Nahn Fermilab

 

Available Downloads:

Room and Building: 
2241 Chamberlin Hall
Host: 
Alex Levchenko
Speaker: Nadya Mason UIUC

 

Available Downloads:

Room and Building: 
2241 Chamberlin Hall
CANCELLED
Host: 
Alex Levchenko
Speaker: Christopher Jarzynski University of Maryland

 

Available Downloads:

Room and Building: 
2241 Chamberlin Hall
Friday, March 27th, 2020
CANCELLED
Host: 
Maxim Vavilov
Speaker: CANCELLED

 

Available Downloads:

Room and Building: 
2241 Chamberlin Hall
Many distant high-energy astrophysical systems (such as pulsar wind nebulae, black-hole accretion flows, and jets from active galactic nuclei) contain collisionless plasmas that are relativistic, radiative, and highly nonthermal. Understanding the nature of turbulence in this extreme plasma physical regime and its implications for observations is an outstanding challenge in plasma astrophysics. Particle-in-cell (PIC) simulations have recently opened this topic to detailed, first-principles numerical and theoretical scrutiny. I will describe the latest progress on understanding relativistic kinetic turbulence. PIC simulations have demonstrated that relativistic turbulence is an efficient particle accelerator, joining the ranks of shocks and magnetic reconnection as a viable source of high-energy particles (and thus broadband radiation and cosmic rays). These simulations are now giving long-awaited tests for a line of analytic theories of stochastic particle acceleration originating with Enrico Fermi in 1949. Relativistic PIC simulations are also giving new insights into two-temperature electron-ion plasmas and radiative turbulence. The next several years promise to bring new breakthroughs into these problems.
Host: 
Jan Egedal
Speaker: Vladimir Zhdankin Princeton

 

Available Downloads:

Room and Building: 
2241 Chamberlin Hall
Neutrinos are unique cosmic messengers that allow to explore the most extreme environments of our Universe. In the past decade, neutrino astronomy has reached a milestone with the discovery of high-energy (TeV-PeV) cosmic neutrinos by the IceCube observatory at the South Pole. The origin of these neutrinos is unknown and subject to much speculation in astroparticle physics. Only recently, IceCube was able to find first compelling evidence of a high-energy neutrino source: the gamma-ray blazar TXS 0506+056. The sum of these observations has implications on the strength and abundance of neutrino sources and their visibility in terms of other messengers: cosmic rays, photons and gravitational waves. Multi-messenger astronomy will play a strong role for future discoveries. In my talk, I will summarize the status of neutrino astronomy and highlight the open questions that can be addressed with next-generation neutrino observatories and detector upgrades. I will emphasize the unique potential of neutrino astronomy as a probe of astrophysics and fundamental physics.
Host: 
Albrecht Karle
Speaker: Markus Ahlers Niels Bohr Institute

 

Available Downloads:

Room and Building: 
2241 Chamberlin Hall
Subatomic-particle research has made enormous progress in the 20th Century by looking inside matter at deeper and deeper levels. It is as if we were peeling the layers of an onion in the hopes of finding more basic rules for the structure of nature. Although the concept of the ultimate building blocks of matter has been modified in several essential respects in the last century, Democritus’s idea remains at the foundation of modern science. Great experiments of the 20th century have led to the discovery of ever-smaller entities that make up what were once thought to be indivisible particles. Moreover, the theory of the very small has been shown to be intimately connected to the largest scales imaginable – cosmology and the beginnings of the Universe. Despite these considerable successes, the current theory has within it the seeds of its own demise and is predicted to break down when probed at even smaller scales. One of such examples is the origin of mass of fundamental particles. We have achieved a beautiful and profound understanding of how fundamental particles acquire their mass, but the mass values remain deeply mysterious. In addition, we learned that ordinary matter supplies only a small fraction of mass in the Universe. We continue to peel away at the more hidden layers of truth with the hope of discovering a more elegant and complete theory. But as is the case with the onion, we must wonder whether there will ever emerge an ultimate layer where the peeling must stop.
Host: 
Tulika Bose
Speaker: Young-Kee Kim U Chicago

 

Available Downloads:

Room and Building: 
2241 Chamberlin Hall
The study of compact stellar remnants such as black holes and neutron stars is an important component of modern astrophysics. Recent observations of the first neutron star merger event and an active galactic nucleus as the first high-energy neutrino source open a new way to study compact objects using multi-messengers. The key to coordinated detection and interpretation of multiple messenger signals, namely, electromagnetic radiation, cosmic rays, neutrinos, and gravitational waves, is to understand the link between the messengers. We try to answer this question from both theoretical and observational perspectives. We study high-energy particle propagation in the vicinity of magnetar-powered transients and black hole jets using numerical simulation. We also investigate analysis frameworks aiming to exploit data across multiple wavelengths and messengers. We close the talk by overlooking the future of Multi-messenger Astrophysics, in light of upcoming facilities such as SWGO and LSST, as well as new questions brought by recent observations.
Host: 
Albrecht Karle
Speaker: Ke Fang Stanford University

 

Available Downloads:

Room and Building: 
2241 Chamberlin Hall

Pages

©2013 Board of Regents of the University of Wisconsin System