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This Week at Physics

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Events During the Week of September 30th through October 7th, 2018

Monday, October 1st, 2018

Plasma Physics (Physics/ECE/NE 922) Seminar
Understanding Heavy Ion Impurity Transport in Tokamaks
Time: 12:05 pm
Place: 2241 Chamberlin Hall
Speaker: Dr. Emily Belli, General Atomics
Abstract: In a fusion reactor, the transport of heavy impurities, such as tungsten from material surfaces, into the high-temperature core must be minimized since accumulation can lead to fuel dilution and radiation losses, ultimately degrading the energy confinement and fusion performance. Assessing the level of core accumulation requires sophisticated transport models beyond those typically use for studying the main ions and plasmas with low-Z impurities. In particular, centrifugal effects due to sonic rotation, which arises in tokamaks from torque due to neutral beam injection for plasma heating, can lead to significant modifications to the simulated transport of heavy impurities. The lack of sonic rotation effects in most theoretical models means that widely-used reduced models are inadequate for studying heavy impurities and thus computationally-intensive advanced kinetic codes are needed. In this work, we use state-of-the art gyrokinetic (turbulent) and neoclassical (collision) codes to develop an understanding of the physical mechanisms driving the particle transport of tungsten in tokamaks and how tungsten accumulation can be avoided Cosponsored by a generous grant from the Women in Science & Engineering Leadership Institute ( WISELI)
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Tuesday, October 2nd, 2018

Chaos & Complex Systems Seminar
Some half-baked philosophy of mathematics
Time: 12:05 pm
Place: 4274 Chamberlin (refreshments will be served)
Speaker: Moe Hirsch, UW Department of Mathematics
Abstract: I'll discuss what I think are the basic philosophical questions:
(1) What makes math universal? Its results seem independent of time and place. No one doubts Euclid's or Pythagoras' theorems of thousands of years ago, even if we think some of the proofs aren't correct. No one since Hitler and Stalin thinks its correctness depends on race, religion or nationality. But will the same math be found wherever there's life in the universe?
(2) Why is math so useful? Try spending a day without thinking about numbers.
(3) Its results seem absolutely true. But are they? If they are, how can we prove it? And if we can prove it, how do we know our proof is correct?
Essays in Humanistic Mathematics: Mathematical Association of America
What is Mathematics Really? R. Hersh, Oxford University Press
Where Mathematics Comes from: G. Lakoff & R Nunez, Basic Books
The Math Gene: K. Devlin, Basic Books
Host: Clint Sprott
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Wednesday, October 3rd, 2018

No events scheduled

Thursday, October 4th, 2018

R. G. Herb Condensed Matter Seminar
Time: 10:00 am
Place: 5310 Chamberlin Hall
Speaker: Roman Lutchyn, Microsoft Station Q
Abstract: TBD
Host: Levchenko
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Friday, October 5th, 2018

Theory Seminar (High Energy/Cosmology)
Title to be announced
Time: 2:00 pm
Place: 5280 Chamberlin Hall
Speaker: Lars Aalsma, University of Amsterdam
Abstract: TBA
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Physics Department Colloquium
Special Event: Julian E. Mack Lecture
The changing flow of energy through the Earth's Climate System
Time: 3:30 pm
Place: 2241 Chamberlin Hall
Speaker: Kevin Trenberth, NCAR
Abstract: Radiant energy from the sun is unevenly absorbed in the Earth system because of the sun-Earth geometry, and the annual and diurnal cycles. The energy is transformed into internal energy (temperature-related sensible heat), latent energy (associated with phase changes of water), potential energy (associated with height and gravity), and kinetic energy (associated with motion). The energy may be stored in atmospheric, ocean, cryosphere and land heat reservoirs and moved around mainly by the atmosphere and ocean, which give rise to our weather and climate. Ultimately it is radiated back to space as infrared radiation, and for a stable climate the global mean outgoing and incoming radiation must balance. However, there is an energy imbalance caused by increasing greenhouse gases in the atmosphere, and most of the imbalance, over 90%, goes into the ocean. Accordingly, ocean heat content (OHC) provides a primary indicator of climate change, along with sea level rise. Regional energy and water imbalances drive heat transports in the atmosphere and ocean currents, and through evaporation, precipitation, and runoff. Natural variability, especially El Niño, plays a small role globally, but can be significant locally. By adopting a holistic approach that includes top-of-atmosphere (TOA) radiation, vertically-integrated atmospheric transports, surface energy fluxes, and ocean heat transports, closure of the energy and water cycles on regional scales can be achieved. A new formulation of the energetics of the atmosphere and the climate system is used to refine estimates of the surface energy fluxes as a residual of TOA and atmospheric energetics. When the surface flux is combined with OHC estimates, ocean heat transports can be computed and validated with in situ observations. Understanding the disposition of the energy imbalance is essential for determining how climate change is manifested.
Host: Alex Levchenko
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