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Events During the Week of April 17th through April 24th, 2016

Monday, April 18th, 2016

Plasma Physics (Physics/ECE/NE 922) Seminar
Fast Reconnection and Self-Generated Turbulence Mediated by the Plasmoid Instability
Time: 12:00 pm
Place:
Speaker: Dr. Amitava Bhattacharjee,, PPPL
Host: UW Madison
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Tuesday, April 19th, 2016

R. G. Herb Condensed Matter Seminar
Semiconductors for Superconducting Qubits
Time: 10:00 am
Place: 5310 Chamberlin Hall
Speaker: Karl Petersson, University of Copenhagen
Abstract: We have developed a superconducting transmon qubit with a semiconductor-based Josephson junction element [1,2]. The junction is made from an InAs nanowire with in situ molecular beam epitaxy-grown superconducting Al contacts. This gate-controlled transmon, or gatemon, allows simple tuning of the qubit transition frequency using a gate voltage to vary the density of carriers in the semiconductor region. In the first generations of devices we have measured coherence times up to 10 µs. These coherence times, combined with stable qubit operation, permit single qubit rotations with fidelities of ~99.5% for all gates including voltage-controlled Z rotations. Towards multi-qubit operation we have also implemented a two qubit voltage-controlled cPhase gate. In contrast to flux-tuned transmons, voltage-tunable gatemons may simplify the task of scaling to multi-qubit circuits and enable new means of control for many qubit architectures.

[1] T. W. Larsen et al., Phys. Rev. Lett. 115, 127001 (2015).
[2] G. de Lange et al., Phys. Rev. Lett. 115, 127002 (2015).
Host: Smith/Coppersmith
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Astronomy Colloquium
TUESDAY TALK
A Philosophically-Informed Appraisal of the Schmidt-Sanduleak Law of Star Formation: "Not Even Wrong"
Time: 12:00 pm
Place: 4421 Sterling Hall
Speaker: Barry F. Madore, Carnegie Observatories and Dept of Astronomy & Astrophysics University of Chicago
Abstract: Galaxy evolution simulations depend critically upon modeling star
formation; however, astronomy does not yet have a "first principles"theory of star formation. One of the most influential parametric descriptions of star formation is the so-called "Schmidt Law", which supposes that the rate of star formation is properly described as a power-law function of the local gas density. I will discuss the popular appeal of the Schmidt Law among galaxy modelers, as well as its observational and conceptual support. But I will then step back and adopt a philosophically-informed stance and make the case that the rather uncritical acceptance of this "law" for more than half a century thwarted a more straightforward, and physically more meaningful interpretation of the empirical data that is now in hand. Viewed and interpreted in the context of cyclical autocatalytic)reaction network I will present new data and new conclusions on the rate of star formation in galaxies deriving explicitly the timescales involved in the cyclical process of star formation and the efficiencies involved in converting gas into stars.
Host: Prof Jay Gallagher
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Chaos & Complex Systems Seminar
Novel-writing as a way to organize data
Time: 12:05 pm
Place: 4274 Chamberlin Hall (refreshments will be served)
Speaker: Russell Gardner, Jr., Freelance scholar
Abstract: This is a follow-up presentation to a CCSS presentation, “Writing a Novel,” in September, 2014. This talk includes lessons learned from that first effort. I call myself a novelist not because I’ve published (yet), but because I have a daily routine of writing (it’s my occupation), have studied the process in readings and courses, and have presented ongoing work to others. The present twelve chapter first draft of a second novel, Different Windows, has been done independently, this time, of any formal class (although I employ a paid editor). Each chapter includes about 25-manuscript pages. I will focus on Novel-writing to organize data and its relations to other forms of scientific, and “ordinary,” means of human data-processing, Fiction as a way to talk publically and formally about matters that worry and interest me, namely, the climate crisis, billionaire denial of the crisis, especially highly influential ones who seek to minimize government in all its forms (Jane Mayer’s Dark Money (2016)), the fate of one’s descendents after one dies, the treatment form of psychoanalysis which has retreated from the forefront of thinking, but which needs representation in an understandable format, and some bleak optimism about a dismal seeming future. Formulations of Professor and Chairman of UW’s Department of English, Caroline Levine, who has written The Serious Pleasure of Suspense (2003). Process of working out a second draft of Different Windows and envisioned attempts to publish the completed work.
Host: Clint Sprott
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Theory Seminar (High Energy/Cosmology)
Evading non-linearities: Baryon Acoustic Oscillations at the linear point
Time: 3:30 pm
Place: 5280 Chamberlin Hall
Speaker: Stefano Anselmi, Case Western Reserve University
Abstract: Cosmology has made fundamental progress thanks to the role of standard rulers. The acoustic peak in the Large Scale Structure clustering correlation function is one of them. However, in the era of precision cosmology, its power has been highly challenged by how late time non-linearities distort the correlation function. Fortunately this is not the end of the story! I will explain how we can evade non-linearities identifying a scale in the correlation function, called the “linear point”, that is an excellent cosmological standard ruler: its position is insensitive to non-linear gravity, redshift space distortions, and scale-dependent bias at the 0.5% level; it is geometrical, i.e. independent of the power spectrum of the primordial density fluctuation parameters. Moreover, the linear point increases its appeal as it is easily identified irrespectively of how non-linearities distort the correlation function. Equally relevant, the correlation function amplitude at the linear point is similarly insensitive to non-linear corrections to within a few percent. Therefore, exploiting the particular Baryon features in the correlation function, we propose three new estimators for growth measurements. We perform a preliminary test in current data finding encouraging results and motivating more careful future investigations.
Host: Amol Upadhye
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Wednesday, April 20th, 2016

Physics Education Innovation Seminar
Best Practices in Large Introductory Physics Courses at the University of Maryland
Time: 12:15 pm
Place: 5310 Chamberlin Hall
Speaker: Rosemary Russ, UW - Madison Department of Curriculum and Instruction
Abstract: Dr. Russ will lead a Q&A session about techniques we might borrow from the University of Maryland for our own large introductory courses. She earned her Ph.D. in Physics at Maryland, working with the Physics Education Research Group.
Host: Peter Timbie
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Thursday, April 21st, 2016

R. G. Herb Condensed Matter Seminar
Quantum optics with ultra-cold atoms
Time: 10:00 am
Place: Chamberlin 5310
Speaker: Alex Kuzmich, University of Michigan
Abstract: The advent of laser cooling thirty years ago enabled studies of properties of ultra-cold atomic gases and led to their applications in metrology and quantum information. Against this backdrop, in the last decade a world-wide effort in using ultra-cold atoms as nonlinear media for single photons has emerged. The near-ideal character of interaction between light and atomic ensembles cooled to micro-Kelvin-scale temperatures permits realization of textbook quantum-optical Hamiltonians while coupling to unwanted environments can be nearly eliminated. In this way ultra-cold atoms have been used for generation of single-photon and entangled light fields, their wavelength conversion and entanglement with atoms, and realization of many-body dynamics and long-term storage of quantum states. Besides offering a rich new system for studying quantum mechanics, these advances may find applications in future information distribution and processing systems.
Host: Saffman
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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:
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
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Friday, April 22nd, 2016

Physics Department Colloquium
First Results from Hitomi
Time: 3:30 pm
Place: 2241 Chamberlin Hall
Speaker: Richard Mushotzky, University of Maryland/Goddard Space Flight Center
Abstract: I will present the Hitomi mission and its present status. Hitomi is a Japanese/US x-ray spectroscopy satellite that was launched in Feb 2016. It carried a wide range of instruments but I will focus on the results from the Soft X-ray Spectrometer, a new technology x-ray spectrometer with an energy resolution of ~4.9 eV ,~30x better than previously achieved in the E>2 keV band. The first observation was that of the Perseus cluster, a nearby very luminous cluster of galaxies and the prototype for the interaction of an active galaxy and the x-emitting hot gas in the cluster. The hot gas is the dominant baryonic component in the cluster and its physical properties are crucial to understanding how clusters, the largest structures in the universe, form and evolve.
The SXS measured for the first time the velocity field of the hot gas and shows the power of precision x-ray spectroscopy . The richness of this data set will allow future measurements of the abundance of several elements to better than 5% precision, constraints on resonance scattering and already has challenged present atomic physics models.
Host: Dan McCammon
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