# This Week at Physics

## Events at Physics |
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### Events on Tuesday, April 24th, 2012

**Chaos & Complex Systems Seminar****Adaptive information****Time:**12:05 pm**Place:**4274 Chamberlin**Speaker:**Rob Nowak, UW Department of Electrical and Computer Engineering**Abstract:**This talk will discuss the notions of adaptive and non-adaptive information in the context of statistical learning and inference. Suppose that we have a collection of models (e.g., signals, systems, representations, etc.) denoted by X and a collection of measurement actions (e.g., samples, probes, queries, experiments, etc.) denoted by Y. A particular model x in X best describes the problem at hand and is measured as follows. Each measurement action, y in Y, generates an observation y(x) that is a function of the unknown model. This function may be deterministic or stochastic. The goal is to identify x from a set of measurements y_1(x),...,y_n(x), where y_i in Y, i=1,...,n. If the measurement actions y_1,...,y_n are chosen deterministically or randomly without knowledge of x, then the measurement process is non-adaptive. However, If y_i is selected in a way that depends on the previous measurements y_1(x),...,y_{i-1}(x), then the process is adaptive. Adaptive information is clearly more flexible, since the process can always disregard previously collected data. The advantage of adaptive information is that it can sequentially focus measurements or sensing actions to distinguish the elements of X that are most consistent with previously collected data, and this can lead to significantly more reliable decisions. The idea of adaptive information gathering is commonplace (e.g., humans and animals excel at this), but outside of simple parametric settings little is known about the fundamental limits and capabilities of such systems. Some preliminary results addressing this situation will be described.**Host:**Sprott**High Energy Seminar****Experimental Muon Physics: an Overview****Time:**3:00 pm**Place:**5310 Chamberlin Hall**Speaker:**David Webber, University of Wisconsin Madison**Abstract:**According to the Standard Model of particle physics, muons behave like

heavy electrons which decay only via the weak force. Their properties

make them especially well-suited to precision measurements of

fundamental parameters of the Standard Model, as well as searches for

physics beyond the Standard Model. Muons have the longest lifetime of

any fundamental particle which still decays, allowing them to form

chemical bound states and probe the structure of the proton.

Additionally, muon decay maximally violates parity, correlating the

decay electron with the muon's spin and enabling measurements of g-2.

In this talk, several recent experimental results will be reviewed,

and some upcoming experiments will be presented.**Host:**Karsten Heeger