Events at Physics
Events During the Week of October 9th through October 16th, 2016
- Graduate Introductory Seminar
- Quantum Computing
- Time: 12:00 pm
- Place: 5280 Chamberln Hall
- Speaker: Coppersmith, Eriksson, Joynt, McDermott, Saffman, Vavilov, Walker, Yavuz
- Plasma Physics (Physics/ECE/NE 922) Seminar
- no seminar
- Time: 12:00 pm
- Place: no seminar
- Speaker: no seminar
- Host: none
- CHEMISTRY EVENT
- What Can Molecular Spectroscopy Tell Us About the Big Bang?
- Time: 11:00 am
- Place: 1315 Chemistry
- Speaker: Eric A. Cornell, JILA| University of Colorado at Boulder | NIST
- Abstract: https://www.chem.wisc.edu/content/what-can-molecular-spectroscopy-tell-us-about-big-bang
- Chaos & Complex Systems Seminar
- Categorizing and visualizing basins of attraction
- Time: 12:05 pm
- Place: 4274 Chamberlin (refreshments will be served)
- Speaker: Anda Xiong, UW Department of Physics
- Abstract: With chaos research, the attention has been most often been given to topics like the chaotic attractor and the Lyapunov exponent, while less attention has been paid to the basin of attraction, yet the latter is essential for determining and calculating the multi-stability of a dynamical system. I will explain the concept of a basin of attraction and show a means for classifying basins into four different types and quantifying their size. I will show examples of attractor basins produced using a 3-D printer including the famous Lorenz system in an unusual regime where three attractors coexist.<br>
- Host: Clint Sprott
- Theory Seminar (High Energy/Cosmology)
- What can we learn from particle physics to study cosmological perturbation theory?
- Time: 3:30 pm
- Place: 5280 Chamberlin
- Speaker: Min-Seok Seo, IBS, Korea
- Abstract: Through the development of the effective field theory of inflation, we can interpret the cosmological perturbation theory as a quantum behavior of the Goldstone boson resulting from the spontaneous breaking of the time translation symmetry. Under this point of view, many wisdoms obtained from the particle physics have been applied to understand the inflationary cosmology. In this talk, we revisit such aspects of the cosmological perturbation theory in the multi-field context, providing more general framework.
- Host: Gary Shiu
- 2016-17 Hilldale Lecture in the Physical Sciences, Free and Open to the Public
- Reversing Climate Change Economically
- Time: 6:00 pm
- Place: WID, H.F. Deluca Forum, 330 North Orchard Street, Madison Reception follows in the Atrium 7-8 pm
- Speaker: Frank Shu, University Professor Emeritus, UC Berkeley and San Diego
- Abstract: 2015 saw an international agreement to limit the mean global temperature rise since the Industrial Revolution to 1.5-2 degrees C. I will present technologies developed by our team that can achieve a reversal of climate change. (1) Supertorrefaction uses the heat capacity of molten salts to convert waste biomass into biocarbon.
(2) Two-fluid molten-salt breeder-reactors operate on the renewable thorium fuel cycle. With a combination of these technologies It should be possible to limit the rise of atmospheric carbon dioxide to 350 ppm before year 2100. Thus, children yet to be born may inherit the climate that the older members of the audience enjoyed when they were young.
- Host: UW Astronomy Department through Hilldale Fund
- Cosmology Journal Club
- An Informal discussion about a broad variety of arXiv papers related to Cosmology
- Time: 12:15 pm
- Place: 5242 Chamberlin Hall
- Abstract: Please visit the following link for more details:
Please feel free to bring your lunch!
If you have questions or comments about this journal club, would like to propose a topic or volunteer to introduce a paper, please email Amol Upadhye (email@example.com).
- Host: Amol Upadhye
- Astronomy Colloquium
- Hilldale Lecturer Frank Shu
- Six Decades of Spiral Density-Wave Theory
- Time: 3:30 pm
- Place: 4421 Sterling Hall, 3:30 pm Coffee and Cookies, Talk starts 3:45
- Speaker: Frank Shu, Hilldale Lecturer, University Professor Emeritus UC Berkely and San Diego
The theory of spiral density waves had its origins about six decades ago in an attempt to reconcile the winding dilemma of material spiral arms in flattened disk galaxies. We begin with the earliest calculations of linear and nonlinear spiral density waves in disk galaxies, in which the hypothesis of quasi-stationary spiral structure (QSSS) plays a central role. We then review the observational implications and tests, in which the prediction of the nonlinear compression of the interstellar medium and its embedded magnetic field was the earliest success, and the failure to detect color gradients associated with the migration of OB stars whose formation is triggered downstream from the spiral shock front seemed to be the earliest failure. We give the reasons for this apparent failure with an update on the current status of the problem of OB star formation, including its relationship to the feathering substructure of galactic spiral arms and giant associations of atomic and molecular gas. Infrared images can show two-armed grand-design spirals, even when the optical and UV images show flocculent structures. We suggest how the nonlinear response of the interstellar gas, coupled with overlapping sub-harmonic resonances, might introduce chaotic behavior in the dynamics of the interstellar medium and Population I objects, even though the underlying forces to which they are subject are regular. We then move to a discussion of resonantly forced spiral density waves in planetary ring and its relation to the ideas of disk truncation, and the shepherding of narrow rings by satellites orbiting nearby. The back reaction of the rings on the satellites led to the prediction of planet migration in protoplanetary disks, which has had widespread application in the exploding data sets concerning hot Jupiters and extrasolar planetary systems. As our final topic, we return to the issue of global normal modes in the stellar disk of spiral galaxies and its relationship to the QSSS hypothesis, where the central theoretical concepts involve waves with negative and positive surface densities of energy and angular momentum in the regions interior and exterior, respectively, to the corotation circle; the consequent transmission and over-reflection of propagating spiral density waves incident on the corotation circle; and the role of feedback from the central regions. We review self-consistent theoretical calculations of slowly growing normal modes in collisionless stellar disks. N-body simulations show that the growth of such modes can saturate at finite amplitudes without the collisional damping of a gaseous interstellar medium as long as N exceeds 3 x107. Lastly, we discuss how the amplitude modulation predicted for the destructive interference of oppositely propagating waves that form standing wave patterns may have been observed in deep infrared images of nearby spiral galaxies.
- Host: UW Astronomy Dept
- Theory Seminar (High Energy/Cosmology)
- *SPECIAL TIME*
- Flavoured squark signatures at the LHC
- Time: 3:30 pm
- Place: 4274 Chamberlin Hall
- Speaker: Gabriel Lee
- Abstract: We present benchmark points for LHC searches from flavored gauge mediation models, in which messenger–matter couplings give flavor-dependent squark masses. Our examples include spectra in which a single squark—stop, scharm, or sup—is much lighter than all other colored superpartners, motivating improved quark flavor tagging at the LHC. Many examples feature flavor mixing; in particular, large stop–scharm mixing is possible. The correct Higgs mass is obtained in some examples by virtue of the large stop A-term. We also revisit the general flavor and CP structure of the models. Even though the A-terms can be substantial, their contributions to EDM’s are very suppressed, because of the particular dependence of the A-terms on the messenger coupling. This holds regardless of the messenger-coupling texture. More generally, the special structure of the soft terms often leads to stronger suppression of flavor- and CP-violating processes, compared to naive estimates.
- Host: Joshua Berger
- R. G. Herb Condensed Matter Seminar
- Nanostructured topological superconductors
- Time: 10:00 am
- Place: 5310 Chamberlin Hall
- Speaker: Ying Liu , Penn State
- Abstract: I will first present measurements on nanoscale superconductors featuring a doubly connected sample topology, focusing on the observation of the destructive regime - the loss of superconductivity near the half flux quanta in ultrasmall doubly connected superconductors - and the Little-Parks-de Gennes effect. I will discuss fundamental questions raised by by this experiment. I will then present our recent work on Sr2RuO4, a leading candidate for chiral p-wave superconductor featuring non-trivial topological properties, especially our magnetoresistance detection of half-flux-quantum states in this material. Finally, I will briefly mention career opportunities at Shanghai Jiao Tong University.
- Host: Mark Friesen
- Physics Department Colloquium
- New Possibilities for Ultra-high Field Superconducting Magnets
- Time: 3:30 pm
- Place: 2241 Chamberlin hall
- Speaker: David Larbalestier, National High Magnetic Field Laboratory
- Abstract: Two recent NRC reports have described the scientific and technology rationales for many new types of ultra-high field magnet: msec 150 T pulsed, pulsed 40 T for neutron or x-ray scattering, regional 32 T superconducting (SC), 40 T SC, 28 – 37 T high-resolution NMR, 25 – 40 T SC for x-rays and neutrons, 60 T DC, 20 T for human MRI, as well as magnets for fusion, particle-accelerators, radiotherapy, axion and other particle detectors. The materials and magnet technology have now made sufficient progress that a few of these magnets are now feasible. I will describe this progress and the various pluses and minuses of the three present high-temperature superconductor types and suggest some timelines under which high field coils beyond the capabilities of present-day Nb-Ti and Nb3Sn magnets might start to make it into commercial fabrication. We have shown that High Temperature Cuprate Superconductors can generate fields >40 T, almost twice the Nb-based superconductor limit and in striking distance of the world record 45 T DC field which requires 28 MW of DC power and a large Nb3Sn superconducting outsert magnet.
- Host: Robert Joynt
- Careers for Physicists
- Discussion of Non-Academic Career Paths w/BOV members
- Time: 5:00 pm
- Place: 5280 Chamberlin Hall
- Speaker: Dr. Jennifer Sebby-Strabley and Dr. Olivia Castellini, Honeywell and the Museum of Science & Industry
- Abstract: Informal conversation with Physics Board of Visitors Members Jennifer Sebby-Strabley and Olivia Castellini. Dr. Sebby-Strabely is a Senior Technical Manager for the Advanced Sensing Technologies group at Honeywell and Dr. Castellini is a Senior Exhibit Developer at the Museum of Science and Industry in Chicago.
- Host: Department of Physics