Events at Physics |
Events During the Week of October 5th through October 12th, 2014
Monday, October 6th, 2014
- Plasma Physics (Physics/ECE/NE 922) Seminar
- Chaotic coordinates for the Large Helical Device
- Time: 12:00 pm - 1:00 pm
- Place: 2535 Engineering Hall
- Speaker: Stuart Hudson, Princeton Plasma Physics Laboratory
- Abstract: <br>
The study of dynamical systems is facilitated by a coordinate framework with coordinate surfaces that coincide with invariant structures of the dynamical flow. For integrable (e.g. axisymmetric) systems, a continuous family of invariant surfaces is guaranteed and action-angle (straight-fieldline) coordinates may be constructed. For non-integrable systems, e.g. stellarators and perturbed tokamaks, this continuous family is broken. Nevertheless,action-angle-like coordinates can still be constructed that simplify the description of the dynamics, where
possible. The Poincare-Birkhoff theorem, the Aubry-Mather theorem, and the KAM theorem show that there are important structures that are invariant under the perturbed dynamics; namely the periodic orbits, the cantori,and the irrational flux surfaces. Coordinates adapted to these invariant sets, which we call chaotic coordinates,provide substantial advantages. The regular motion becomes straight, and the irregular motion is bounded by, and dissected by, coordinate surfaces that coincide with surfaces of locally-minimal magnetic-fieldline flux. Chaotic coordinates are based on almost-invariant surfaces. The theory of quadratic-flux-minimizing (QFM)surfaces is reviewed, and the numerical techniques that allow high-order QFM surfaces to be
constructed for chaotic magnetic fields of experimental relevance are described. As a practical example, the chaotic edge of the
magnetic field as calculated by HINT2 code in the Large Helical Device (LHD) is examined. The theoretical and numerical techniques for finding the boundary surface are implemented, and a coordinate system based on a selection of QFM surfaces is constructed that simplifies the description of the magnetic field; so that, to a good approximation, the flux surfaces (including the last closed flux surface) become straight and the islands become ‘square’. - 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 Le Zhang (lzhang263@wisc.edu) - Host: Peter Timbie
- Outreach event: movie show
- Bringing the Universe to Wisconsin presents "Chasing the Ghost Particle"
- Time: 7:30 pm - 8:30 pm
- Place: Union South Marquee Theater
- Abstract: Celebrate the successful completion of the “Bringing the Universe to Wisconsin” public event series. All 26 campuses and communities in the UW system were visited by members of the Wisconsin IceCube Particle Astrophysics Center, WIPAC. The generous support from the Ira and Ineva Reilly Baldwin Wisconsin Idea Endowment enabled citizens to hear firsthand from WIPAC scientists, engineers, IT professionals, staff, and students about new ways of viewing the Universe.
- Host: Education and Outreach, WIPAC
Tuesday, October 7th, 2014
- Chaos & Complex Systems Seminar
- Using distance correlation and SS-ANOVA to assess associations of familial relationships, lifestyle factors, diseases and mortality
- Time: 12:05 pm - 1:00 pm
- Place: 4274 Chamberlin Hall (Refreshments will be served)
- Speaker: Jing Kong, UW Department of Statistics
- Abstract: We present a method for examining mortality as it is seen to run in families, and lifestyle factors that are also seen to run in families, in a sub-population of the Beaver Dam Eye Study that has died by 2011. We observe that pairwise distance between death age in related persons is on average less than pairwise distance in death age between random pairs of unrelated persons. Our goal is to examine the hypothesis that pairwise di fferences in lifestyle factors correlate with the observed pairwise diff erences in death age that run in families. Szekely and coworkers have recently developed a method called distance correlation, that is suitable for this task with some enhancements relevant to the particular task at hand. We build a Smoothing Spline ANOVA (SS-ANOVA) model for predicting death age based on four major lifestyle factors generally known to be related to mortality and four of the major diseases contributing to mortality, to develop a lifestyle mortality risk vector and a disease mortality risk vector. We then examine to what extent pairwise diff erences in these scores correlate with the pairwise di fferences in mortality as they occur between family members and between unrelated persons. We fi nd signfi cant distance correlations between death ages, lifestyle factors, and family relationships. Considering only sib pairs compared to unrelated persons, distance correlation between siblings and mortality is, not surprisingly, stronger than that between more distantly related family members and mortality. The overall methodological approach here easily adapts to exploring relationships between multiple clusters of variables with observable (real-valued) attributes, and other factors for which only possibly nonmetric pairwise dissimilarities are observed.
- Host: Clint Sprott
- Theory Seminar (High Energy/Cosmology)
- The Higgs, Flavor and Large At in Extended GMSB
- Time: 3:00 pm - 4:00 pm
- Place: 5280 Chamberlin Hall
- Speaker: Jared Evans
- Abstract: The observed Higgs at 126 GeV requires large tuning in the MSSM. This tuning is particularly bad in gauge mediated SUSY breaking (GMSB), as the large A-terms that can ameliorate this tuning are absent at the messenger scale. Extending GMSB through the addition of superpotential couplings between the MSSM and messenger superfields can generate these A-terms to reduce the severity of the tuning problems in GMSB. There are a variety of couplings that one can consider, but those best for tuning provide a source of flavor violation beyond the standard model Yukawas. However, there are several features of the extended GMSB models that allow them to relax the SUSY flavor problem. I will review extended GMSB, discuss these flavor issues in detail, and also discuss some of the phenomenological prospects for discovering these models.
- Host: Ran Lu
Wednesday, October 8th, 2014
- No events scheduled
Thursday, October 9th, 2014
- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- Clusters of galaxies as tools for cosmology
- Time: 2:30 pm - 3:30 pm
- Place: 5280 Chamberlin Hall
- Speaker: Mel Ulmer, Northwestern
- Abstract: Clusters of galaxies are the largest gravitationally bound systems in the Universe. Due to their large masses (~1E15 suns), they distort the background galaxies images. The distortion (lensing) depends among other things on the angular distance to the galaxies versus redshift. The effect can be used to set limits to the Dark Energy equation of state w and even dw/dz. The exciting aspect is that the effect is purely geometrical. As such, it requires essentially no input physics to interpret the results. The approach is so obviously interesting that the fact it has not yet led to a definitive result indicates it must be difficult! We discuss our own group’s efforts and goals (http://cencosw.oamp.fr/DAFT/) and why the concept is difficult to carry out in practice. We also present one “fun” result based on using lensing and other techniques to measure the detailed mass distribution in a cluster. The mass distribution versus radius we find is such that the ratio of baryons to Dark Matter (DM) is not constant on large (1,000s of light years) scales. This result raises the specter that perhaps in our location of the Milky Galaxy the ratio of DM/baryons also deviates from the comic average.
- Host: Dan McCammon
- Astronomy Colloquium
- Puzzles in the Structure of Disk Galaxies
- Time: 3:30 pm - 5:00 pm
- Place: 4421 Sterling Hall
- Speaker: Stephane Courteau, Queen's University
- Abstract: Galaxies can be described in terms of their structure, dynamics<br>
and stellar populations. Some very robust correlations between<br>
various galaxy structural properties, such as total luminosity,<br>
maximum circular velocity, and size show rather small scatter,<br>
hinting at well-regulated galaxy formation processes. A major<br>
challenge to understanding these scaling relations, and ultimately<br>
galaxy formation and evolution, is the elusive interplay between<br>
visible and dark matter. I will discuss the latest derivations<br>
of galaxy scaling relations and their link with modern<br>
cosmological models. - Graduate Introductory Seminar
- Atomic, Molecular, and Optical Physics
- Time: 4:30 pm - 5:30 pm
- Place: 5280 Chamberlin Hall
- Speaker: Lawler, Lin, Saffman, Walker, Yavuz
Friday, October 10th, 2014
- Physics Department Colloquium
- Neutrino Oscillations at Work
- Time: 3:30 pm - 4:30 pm
- Place: 2241 Chamberlin Hall (coffee at 4:30 pm)
- Speaker: Jenny Thomas, University College London
- Abstract: The observation that the three types of neutrino flavor oscillate among themselves led to the realization that neutrinos have a very small but non-zero mass. This is extremely important because the supremely successful Standard Model of particle physics had expected, and indeed needed, the neutrinos to have exactly zero mass. Since the discovery of neutrino oscillations over the last 15 years, the parameters of the oscillations have been sufficiently well measured to turn neutrino oscillations into a tool for learning more about the elusive neutrino. I will explain the concept of neutrino oscillations, and report on the recent results from around the world in context with the new challenges now facing researchers of inferring the remaining unknown<br>
neutrino properties. I will talk briefly about an exciting new project on the horizon for the very near future. - Host: Karle