Events at Physics |
Events During the Week of April 16th through April 23rd, 2017
Monday, April 17th, 2017
- Plasma Physics (Physics/ECE/NE 922) Seminar
- Multi-Scale Plasma Modeling
- Time: 12:00 pm - 12:55 pm
- Place: 2317 Engineering Hall
- Speaker: Dr. Gian Luca Delzanno, Los Alamos National Laboratory, USA
- 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
Tuesday, April 18th, 2017
- Council Meeting
- Place: 2314 Chamberlin hall
- Chaos & Complex Systems Seminar
- Life inside the black box: Soil microbes, climate change, and fire
- Time: 12:05 pm - 1:00 pm
- Place: 4274 Chamberlin (refreshments will be served)
- Speaker: Thea Whitman, UW Department of Soil Science
- Abstract: Although charcoal is renowned for its persistence and stability in soils, it is actually a dynamic and heterogeneous material. Today, pyrolyzed organic matter is important not only in fire-affected ecosystems, but also in managed systems, where it may be produced intentionally as an agricultural soil amendment or for carbon management / climate change mitigation. How soil microbes respond to these inputs is critical for determining the net climate impact, and is only just being revealed, through advances in stable isotope and high-throughput sequencing techniques.<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. <br>
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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)
- Ubiquity of non-geometry in heterotic string compactifications
- Time: 3:30 pm
- Place: 5280 Chamberlin
- Speaker: Stefano Massai, University of Chicago
- Abstract: I will address the problem of classifying supersymmetric string compactifications in regions of moduli space where the supergravity approximation breaks down. I will show evidence that, in the heterotic string, quantum effects generically turns a Calabi-Yau manifold into a T-fold, a non-geometric space defined by T-duality transition functions. I will describe a non-geometric version of ADE singularities, and show a full classification of the six-dimensional super-conformal field theories that describe the low energy physics on such defects.
Wednesday, April 19th, 2017
- Department Meeting
- Time: 12:15 pm
- Place: 5310 Chamberlin hall
- Speaker: Albrecht Karle
Thursday, April 20th, 2017
- R. G. Herb Condensed Matter Seminar
- Entangling approaches for capacitively coupled semiconductor spin qubits
- Time: 10:00 am
- Place: 5310 Chamberlin
- Speaker: Vanita Srinivasa, Sandia
- Abstract: Many proposed realizations of quantum information processing rely on rapid and robust entanglement of coherent qubits over a wide range of distances. While implementations based on electron spins in solids can take advantage of both the relative isolation of spin qubits from their environment and rapid control of the electron charge, entangling mechanisms in these systems are often limited in range and remain susceptible to charge-based decoherence. I will describe our theoretical approaches to addressing these challenges for spin qubits encoded in multiple electrons within systems of coupled quantum dots. We analyze a new regime for capacitive coupling of two-electron spin qubits that leads to high theoretical fidelities for entangling gates within silicon-based implementations in the presence of charge noise and relaxation. We also show that the three-electron resonant exchange qubit provides both a protected operating point for rapid single-qubit manipulation and an electric dipole moment that enables multiple approaches for long-range entangling gates via a superconducting microwave resonator. These methods are inspired by techniques from circuit quantum electrodynamics, Hartmann-Hahn double resonance in NMR, and the Cirac-Zoller gate for trapped ions.
- Host: Coppersmith
- Astronomy Colloquium
- Galaxy Transformations And The Quenching of Star Formation at High Redshift
- Time: 3:30 pm - 5:00 pm
- Place: 4421 Sterling Hall, Coffee and Cookies 3:30 PM, Talk at 3:45 PM
- Speaker: Mauro Giavalisco, University of Massachusetts
- Abstract: There is convincing evidence that massive galaxies (i.e. M~M*) undergo profound structural and morphological transformations as their star formation activity comes to a halt and they enter a phase of passive evolution. We do not yet understand which physical mechanism, or mechanisms, among a number of plausible ones, are responsible for the quenching. Nor do we understand what drives the morphological transformations. In this talk I will review some recent observations of both structural and morphological transformations and of quenching in galaxies at redshift 1<z<2.5, namely at the peak of the cosmic star formation activity, and discuss possible interpretations for the underlying physics of both. I will also present very recent observations that are informing us on the joint evolution of dark and baryon matter in galaxies and point to a possible common origin for both quenching and structural transformations. I will conclude by discussing some of the interpretations and by offering my speculations.
- Host: Astronomy Dept
Friday, April 21st, 2017
- Physics Department Colloquium
- Carbon Dioxide – A Force for Global Change Throughout the Earth’s Atmosphere
- Time: 3:30 pm
- Place: 2241 Chamberlin Hall
- Speaker: Martin Mlynczak, NASA Langley Research Center
- Abstract: The concentration of carbon dioxide, CO2, has been increasing in Earth’s atmosphere since the beginnings of the Industrial Revolution in the late 1700’s. Largely due to the burning of fossil fuels, the amount of CO2 in the atmosphere as measured by its volume mixing ratio has increased from 280 parts per million (ppm) around the year 1800 to over 400 ppm today. CO2 strongly absorbs infrared radiation near the peak of Earth’s emission spectrum. Increases in CO2 result in additional capture of energy emitted by Earth’s surface, and ultimately lead to a warming of the Earth’s surface and lower atmosphere. A key estimate as to the degree to which increasing CO2 causes climate change is expressed in the concept of “radiative forcing”, which is defined as the change in net radiative energy within the climate system associated with the buildup of CO2. The concept of radiative forcing (RF), and its accurate computation, are the benchmarks upon which all of climate change science rests. In this talk we will examine the computation of RF and discuss some fundamental physical principles (including the first law of thermodynamics; the Heisenberg uncertainty principle; and the harmonic oscillator) underlying these calculations. We will progress through some rather complex calculations conducted at high spectral resolution to elucidate the uncertainty associated with our understanding and knowledge of RF. Lastly, we will discuss the radiative effects of increased CO2 on Earth’s high atmosphere (above 100 km altitude), which leads to cooling aloft, with long-term consequences for space flight operations.
- Host: Susan Nossal