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This Week at Physics

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Events During the Week of November 18th through November 24th, 2018

Monday, November 19th, 2018

Plasma Physics (Physics/ECE/NE 922) Seminar
Wave generation and heat flux suppression in astrophysical plasma systems
Time: 12:05 pm
Place: 2241 chamberlin hall
Speaker: Gareth Roberg-Clark , Univ. Maryland
Abstract: Heat flux suppression in collisionless plasmas for a large range of plasma beta is explored using two-dimensional particle-in-cell simulations with a strong, sustained thermal gradient. We find that a transition takes place between whistler-dominated (high-beta) and double-layer-dominated (low-beta) heat flux suppression. Whistlers saturate at small amplitude in the low beta limit and are unable to effectively suppress the heat flux. Electrostatic double layers suppress the heat flux to a mostly constant factor of the free streaming value once this transition happens. The double layer physics is an example of ion-electron coupling and occurs on a scale of roughly the electron Debye length. The scaling of ion heating associated with the various heat flux driven instabilities is explored over the full range of beta explored. The range of plasma-betas studied in this work makes it relevant to the dynamics of a large variety of astrophysical plasmas, including the intracluster medium of galaxy clusters, hot accretion flows, stellar and accretion disk coronae, and the solar wind.
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Tuesday, November 20th, 2018

Theory Seminar (High Energy/Cosmology)
Deriving the WGC from holographic entanglement entropy
Time: 11:00 am
Place: 5310 Chamberlin Hall
Speaker: Miguel Montero, KU Leuven
Abstract: The Weak Gravity Conjecture (WGC) is a proposed constraint on effective field theories that can be consistently coupled to quantum gravity, requiring the presence of superextremal particles. This particles allow extremal black holes to decay, but so far the relationship has only been understood heuristically. I will explain how this connection can be made precise, in the context of asymptotically AdS quantum gravity: The black hole must be allowed to decay to comply with quantum information theorems in the dual CFT. I will discuss the connection to the ER=EPR proposal and how this avenue can lead to new Swampland constraints.
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Chaos & Complex Systems Seminar
Ergodicity in chaotic oscillators
Time: 12:05 pm
Place: 4274 Chamberlin (Refreshments will be served)
Speaker: Clint Sprott, UW Department of Physics
Abstract: The harmonic oscillator is the simplest and most common nontrivial dynamical system. The prototypical mechanical example is a mass suspended by a spring, but the same dynamics occur in most musical instruments, many electronic devices, models of economic and ecological systems, some chemical reactions, and many other real-world systems. However, most oscillations in nature are not simple but rather exhibit aperiodic fluctuations such as the weather and the stock market. I will describe a new model of a chaotic oscillator whose behavior is identical to a harmonic oscillator in equilibrium with a source of heat at a constant temperature. It represents the culmination of a 30-year search for an elegant chaotic model whose solution is ergodic and whose variables accurately exhibit a normal (Gaussian) distribution as expected for a truly random process.
Host: Clint Sprott
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Wednesday, November 21st, 2018

No events scheduled

Thursday, November 22nd, 2018

No events scheduled

Friday, November 23rd, 2018

No events scheduled
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