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This Week at Physics

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Events During the Week of April 29th through May 6th, 2012

Monday, April 30th, 2012

R. G. Herb Condensed Matter Seminar
Formation of Magnetic Microphases in Ca$_3$Co$_2$O$_6$
Time: 4:30 pm
Place: 5310 Chamberlin
Speaker: Yoshitomo Kamiya, Los Alamos National Lab
Abstract: We study a frustrated quantum Ising model relevant for Ca$_3$Co$_2$O$_6$ that comprises a triangular lattice of weakly-coupled ferromagnetic chains. According to our quantum Monte Carlo simulations, the chains become ferromagnetic and form a three-sublattice "up-up-down'' structure below a temperature $T=T_{ ext{CI}}$. In contrast, long-period spin-density-wave (SDW) modulations along the chains are stabilized for $T_ ext{CI} < T < T_c$ in agreement with recent experiments by Agrestini et al [1]. Our mean field solutions reveal quasi-continuous change of the periodicity as a function of $T$, implying the existence of metastable states in the SDW phase that explains the very slow low-temperature dynamics that has been observed in Ca$_3$Co$_2$O$_6$ [2]. Closely related multiferroic materials Lu$_2$MnCoO$_6$ [3] and Ca$_3$MnCoO$_6$ [4] will also be discussed.

References:
[1] S. Agrestini et al., Phys. Rev. Lett., 101, 097207 (2008)
[2] T. Moyoshi and K. Motoya, J. Phys. Soc. Jpn., 80, 034701 (2011)
[3] S. Yanez-Vilar et al., Phys. Rev. B, 84, 134427 (2011)
[4] Y. J. Jo et al., Phys. Rev. B. 79, 012407 (2009)
Host: Perkins
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Tuesday, May 1st, 2012

Chaos & Complex Systems Seminar
From dragonfly eyes to fish eyes: a summary of ways to understand social-ecological systems across disciplinary lines
Time: 12:05 pm
Place: 4274 Chamberlin
Speaker: Bethany Laursen, UW Department of Forest and Wildlife Ecology
Abstract: When researching approaches to complex, social-ecological problems, the plethora of interdisciplinary paradigms can leave even savvy academicians confused or more entrenched in familiar ideas than innovative solutions. University extension agents, often trained in traditional disciplines at the masteraEuroTMs degree level and daily surrounded by tangible rather than theoretical entities, are even harder pressed to understand how these new fields relate to more familiar ones. However, extension agents are also precisely the people most likely to integrate various academic approaches by working in complex, real-world problem-solving situations. It is thus useful and necessary for agents to be able to compare, contrast, and integrate the various epistemologies encountered in social-ecological systems research. I demonstrate a decision support tool that agents can use for this purpose with six example fields of inquiry (environmental history, political ecology, social-ecological systems theory, rural sociology, ecological economics, and adaptive co-management). In addition to aiding an individualaEuroTMs understanding, the tool also promotes collective learning and collaboration by enabling shared understanding; each collaborator can use it to become more aware of their own epistemology and those of others. Through further group negotiation, this awareness minimizes epistemological aEurooeblind-spotsaEuro and vitriol, and it maximizes adaptive problem solving.
Host: Sprott
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"Physics Today" Undergrad Colloquium (Physics 301)
Magnetic Confinement in Plasma Physics
Time: 1:20 pm
Place: 2223 Chamberlin
Speaker: Karsten McCollam, University of Wisconsin Department of Physics
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Wednesday, May 2nd, 2012

Department Meeting
Time: 12:15 pm
Place: 5310 Chamberlin Hall
Agenda: http://www.physics.wisc.edu/twap/agendas/2289.pdf
Minutes: http://www.physics.wisc.edu/twap/minutes/2289.pdf
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Thursday, May 3rd, 2012

R. G. Herb Condensed Matter Seminar
Non-classical noise in quantum optomechanical systems
Time: 10:00 am
Place: 5310 Chamberlin
Speaker: Aashish Clerk, McGill University
Abstract: A key goal in the fields of quantum optomechanics and electromechanics is to measure and hopefully control truly quantum behaviour in a "large" mechanical resonator. In this talk, I will start by giving a quick introduction to these two rapidly growing fields. I will then discuss recent experimentally-motivated theoretical work which calculates the full statistics of low-frequency energy fluctuations of a driven, quantum resonator. Surprisingly, these fluctuations are highly non-classical: they are most naturally described by a quasi-probability distribution, which can be negative. Somewhat surprisingly, this effect has a close relationship to the statistics of electronic charge transfer (so-called "full counting statistics") in mesoscopic superconducting conductors. I will discuss how these effects might be measured, and how they represent a kind of non-classical behaviour similar to the violation of a Leggett-Garg inequality. While the emphasis is on phonons, our results apply equally as well to the photon fluctuations of a driven cavity.
Host: Vavilov
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Astronomy Colloquium
Here be dragons :The Dynamic Radio Sky
Time: 3:30 pm
Place: 4421 Sterling Hall
Speaker: Geoffrey Bower, University of California - Berkeley
Abstract: Radio variability probes a wide range of astrophysical phenomena from the solar system to the early Universe including black holes, neutron stars, gravitational wave sources, and relativistic shocks from collapsing stars. Radio follow-up of events discovered at optical, X-ray, and gamma-ray wavelengths demonstrates a rich phenomenology but we lack a systematic and sensitive view of radio variability. Our efforts in recent years with the Very Large Array (VLA) and the Allen Telescope Array (ATA) have provided the beginnings of an unbiased exploration on time scales from milliseconds to decades. Powered by development of unique digital instrumentation, new algorithms, and new survey strategies, our surveys have defined the shape of next generation radio telescopes and surveys. In particular, these surveys are shaping our understanding of radio supernovae, tidal disruption events, and gravitational-wave sources. Planned surveys with newly commissioned national facilities such as the Expanded Very Large Array (EVLA), the Australian SKA Pathfinder (ASKAP), and the South African MeerKAT telescopes coupled with the development of new instrumentation will extend our reach into new parameter space.

Host: Eric Wilcots
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Friday, May 4th, 2012

Cosmology Journal Club
An Informal discussion about a broad variety of arXiv papers related to Cosmology
Time: 12:00 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 Le Zhang (lzhang263@wisc.edu)
Host: Peter Timbie
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Theory Seminar (High Energy/Cosmology)
VBFNLO: vector boson fusion and more
Time: 1:00 pm
Place: 5280 Chamberlin Hall
Speaker: Dieter Zeppenfeld, Karlsruhe Institute of Technology
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NPAC (Nuclear/Particle/Astro/Cosmo) Forum
CANCELED
Uncovering the nature of neutrinos via double beta decay
Time: 2:00 pm
Place: 4274 Chamberlin
Speaker: Allen Caldwell, Director, Max Planck Institute for Physics, Munich, Germany
Abstract: Whether or not the neutrino is a Majorana particle is a fundamental question in particle physics. The search for neutrinoless double beta decay is a direct attempt to answer this question. The GERDA experiment, which started taking data last year, is such a search. After an introduction, the experiment status and plans will be described.
Host: Westerhoff
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Physics Department Colloquium
2012 Distinguished Alumni Award Winner
Alumni Award Speaker
Time: 4:00 pm
Place: 2241 Chamberlin Hall (coffee at 3:30 pm)
Speaker: Ronald Lockwood, Lincoln Laboratory, Massachusetts Institute of Technology
Abstract: Imaging spectroscopy is a sophisticated tool used to address a broad range of scientific questions in remote sensing. Imaging spectroscopy is an evolution of the multi-spectral imagers that are commonly employed for remote sensing such as NASA's LandSat series. This talk is a broad overview of the technology including a conceptual introduction, a review of the optical forms that are generally applied with a more detailed description of the Chrisp-Offner design, a description of the established techniques employed for both the laboratory and field (vicarious) calibration in order to convert the raw data to physical units, the removal of the deleterious effects of the atmosphere through the application of the principles of radiative transfer, and the techniques used for performing material detection.
Host: Lin
Poster: http://www.physics.wisc.edu/twap/posters/2012/2199.pdf
Video: http://www.physics.wisc.edu/vod/2012/05/04.html
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"This Week at Physics" poster: http://www.physics.wisc.edu/twap/posters/2012/2012-04-30.pdf

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