Events at Physics |
Events During the Week of April 2nd through April 9th, 2017
Monday, April 3rd, 2017
- Plasma Physics (Physics/ECE/NE 922) Seminar
- Fast Ion Confinement in Tokamaks
- Time: 12:00 pm - 12:55 pm
- Place: 2317 Engineering Hall
- Speaker: Dr. Benedikt Geiger, Max-Planck Institute for Plasma Physics, Garching, Germany
- Cosmology Journal Club
- An Informal discussion about a broad variety of arXiv papers related to Cosmology
- Time: 12:15 pm - 1:15 pm
- Place: 5242 Chamberlin Hall
- Abstract: Please visit the following link for more details:
http://cmb.physics.wisc.edu/journal/index.html
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 (aupadhye@wisc.edu). - Host: Amol Upadhye
- Theory Seminar (High Energy/Cosmology)
- Hidden Valley searches at the LHCb
- Time: 3:30 pm
- Place: 4274 Chamberlin (SPECIAL LOCATION AND DATE)
- Speaker: Yue Zhao, University of Michigan
- Abstract: Dark shower is a generic feature of the Hidden Valley (HV) models. It has interesting implications on collider studies on Neutral Naturalness models. Bound states in the hidden sector are produced with a high multiplicity, low masses, and long lifetimes. A collider search of such signals requires good vertex resolution, low energy threshold, as well as a good particle id to veto the background. We show that the LHCb provides an ideal environment to study HV models. Further, we compare the sensitivities at the LHCb with those at the ATLAS/CMS.
Tuesday, April 4th, 2017
- Council Meeting
- Time: 12:00 pm
- Place: 2314 Chamberlin hall
- Chaos & Complex Systems Seminar
- “Wet chaos”: Characteristics of extreme rains in a changing climate
- Time: 12:05 pm - 1:00 pm
- Place: 4274 Chamberlin (refreshments will be served)
- Speaker: John Young, UW Department of Atmospheric and Oceanic Science
- Abstract: Edward Lorenz (1917- 2008) produced a series of theoretical papers on the predictability of idealized weather systems which led him to be known as a “Father of Chaos”. He concentrated on weather circulation models which yielded non-periodic behavior. Since “climate” is simply the long-term statistics of weather variability, it also reflects chaos properties which include irregularity of extreme states.<br>
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The implication for real weather systems is that precipitation, an important climate variable and by-product of rising moist air, possesses some form of chaos. This is made more complex because precipitating weather releases condensational heating, a positive feedback on the circulation. The properties of chaotic precipitation necessarily depend on the wide varieties space and time scales, ranging from local transient torrential thunderstorms to regional monthly heavy rain totals.<br>
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The edges of the attractor basin of precipitation are important because of their impact on ecology and human activities. Examples show how the probability distributions of heavy rain differ greatly from those of temperature, wind, etc. These empirical distributions are uncertain due to limited data length (e.g., 120 years) and improbability of extreme events.
Some questions of interpretation for power law-like relations and dependence on duration will be discussed. Finally, the implications of a temperature-dependent water vapor constraint suggest how global warming may lead to increasing limits of extreme precipitation. - Host: Clint Sprott
- Theory Seminar (High Energy/Cosmology)
- Next steps in new physics searches, LHC and beyond.
- Time: 3:30 pm
- Place: 5280 Chamberlin
- Speaker: Liantao Wang, University of Chicago
- Abstract: Starting from the most recent LHC results reported in Moriond 2017, I will give my perspective the status of new physics searches and discuss the strategies for the future.
Wednesday, April 5th, 2017
- Department Meeting
- Time: 12:15 pm
- Place: 5310 Chamberlin hall
- Speaker: Albrecht Karle
Thursday, April 6th, 2017
- R. G. Herb Condensed Matter Seminar
- Coherent coupling between a quantum dot and a donor in silicon
- Time: 10:00 am
- Place: 5310 Chamberlin Hall
- Speaker: Patrick Harvey-Collard, Sandia National Labs
- Abstract: Individual donors and quantum dots in silicon chips are used as bits of quantum information with different but complementary advantages. In this work, we show that these two qubit systems can be combined by demonstrating the coherent interaction of a 31P donor electron with the electron of a metal-oxide-semiconductor quantum dot. We form a qubit from the spin singlet and triplet states of the two-electron system. We show that the donor nuclear spin drives coherent rotations between the electronic qubit states through the contact hyperfine interaction. This provides every key element for compact two-electron spin qubits requiring only a single dot and no additional magnetic field gradients, as well as a means to interact with the nuclear spin qubit. This system furthermore introduces an engineered path to couple donors together, alleviating the need for challenging atomic-precision fabrication and providing a scalable path to multi-donor qubit systems.
In this talk, I will also discuss our advances in engineering the valley splitting and the shell filling of QDs to overcome the system’s challenges. I will present a scheme for high fidelity spin readout that combines the advantages of the Pauli blockade and spin 1/2 readouts.
This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. DOE under contract DE-AC04-94AL85000.
- Host: Coppersmith
- Astronomy Colloquium
- Turbulence and Dynamo Action in Accretion Flows
- Time: 3:30 pm - 5:00 pm
- Place: 4421 Sterling Hall, Coffee and cookies at 3:30 PM, Talk begins at 3:45 PM
- Speaker: Fausto Cattaneo, University of Chicago
- Abstract: Accretion is an important process in astrophysics: it allows the growth of compact objects and it powers some of the most energetic phenomena in the universe. Often the accreting material comes from a disk. In this case the accretion rate is controlled by the outward flux of angular momentum. Collisional process, like viscosity, are many orders of magnitude too small to provide the efficient angular momentum transport required to account for the observed accretion rates. Thus it is commonly assumed that the transport in an accretion disk is mediated by some form of turbulence. The nature of this turbulence is a matter of intense debate. In electrically conducting disks, its origin is most likely related to the Magneto Rotational Instability (MRI), which requires that the disk be threaded by a coherent weak magnetic field. This raises the interesting possibility that the disk turbulence, through dynamo action, may be able to generate the very magnetic filed that is necessary for the instability to develop. This process of self-sustaining magnetization has indeed been observed in numerical simulations. However many issues remain, the most notable of which are the ability of the MRI driven dynamo to operate in the limit of high electrical conductivity and the efficiency of the angular momentum transport. In this talk I shall describe some of the efforts to date to address these issues.
- Host: UW Astronomy Department
Friday, April 7th, 2017
- Physics Department Colloquium
- Quark Gluon Plasma: Surprises from strongly coupled QCD matter
- Time: 3:30 pm
- Place: 2241 Chamberlin hall
- Speaker: Barbara Jacak, UC-Berkeley/LBL
- Abstract: Quantum Chromodynamics has long predicted a transition from normal hadronic matter to a phase where the quarks and gluons are no longer bound together and can move freely. Quark gluon plasma is now produced regularly in collisions of heavy nuclei at very high energy at both the Relativistic Heavy Ion Collider (RHIC) in the U.S. and at the LHC in Europe.
Quark gluon plasma exhibits remarkable properties. Its vanishingly small shear viscosity to entropy density ratio means that it flows essentially without internal friction, making it one of the most “perfect” liquids known. It is also very opaque to transiting particles including heavy charm quarks, though the exact mechanism for this is not yet understood. Recent data suggest that even very small colliding systems may produce a droplet of plasma. The similarities to strongly coupled or correlated systems in ultra-cold atoms and condensed matter are striking, and have inspired novel theoretical descriptions growing out of string theory. It remains a mystery how this plasma emerges from cold, dense gluonic matter deep inside nuclei. I will discuss current knowledge about interactions of quarks and gluons within the plasma and how a future electron-ion collider can help address this question.
- Host: Baha Balantekin
