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Mathematics Colloquium

All colloquia are on Fridays at 4:00 pm in Van Vleck B239, unless otherwise indicated.

Fall 2015

Go to next semester, Spring 2016.

date speaker title host(s)
September 4 Isaac Goldbring (UIC) On Kirchberg's embedding problem Andrews/Lempp
September 11 Doron Puder (IAS) Word-Measures on Groups Gurevich
September 18 Izzet Coskun (UIC) The geometry of points in the plane Erman
September 25 Abbas Ourmazd (UW-Milwaukee) Structure and Dynamics from Random Observations Mitchell
October 2
October 9 Igor Mezic (UC Santa Barbara) Budisic, Thiffeault
October 16 Hadi Salmasian (Ottawa) Gurevich
October 23 L Wang (UW) Wisconsin Science Festival.
October 30 Ruth Charney (Brandeis) Dymarz
November 6 Reserved *S
November 13 Reserved *T
November 20 Reserved
November 27 University Holiday No Colloquium
December 4 Reserved
December 11 Reserved


September 4: Isaac Goldbring (UIC)

Title: On Kirchberg's embedding problem

Abstract: In his seminal work on the classification program for nuclear C*-algebras, Kirchberg showed that a particular C*-algebra, the Cuntz algebra O2, plays a seminal role. Subsequent work with Chris Phillips showed that O2 also plays a prominent role in regards to the wider class of exact C*-algebras, and this led Kirchberg to conjecture that every C*-algebra is finitely representable in O2, that is, is embeddable in an ultrapower of O2. The main goal of this talk is to sketch a proof of a local finitary reformulation of this conjecture of Kirchberg. The proof uses model theory and in particular the notion of model-theoretic forcing. No knowledge of C*-algebras or model theory will be assumed. This is joint work with Thomas Sinclair.

September 11: Doron Puder (IAS)

Title: Word-Measures on Groups.

Abstract: Let w be a word in the free group on k generators, and let G be a finite (compact) group. The word w induces a measure on G by substituting the letters of w with k independent uniformly (Haar) chosen random elements of G and evaluating the product. Questions about word-measures on groups attracted attention in recent years both for their own sake and as a tool to analyze random walks on groups.

We will explain some properties of word-measure, give examples and state conjectures. We will also talk about recent results regarding word-measures on symmetric groups and word-measures on unitary groups.

September 18: Izzet Coskun (UIC)

Title: The geometry of points in the plane

Abstract: Grothendieck's Hilbert scheme of points is a smooth compactification of the configuration space of points in the plane. It has close connections with combinatorics, representation theory, mathematical physics and algebraic geometry. In this talk, I will survey some of the basic properties of this beautiful space. If time permits, I will discuss joint work with Arcara, Bertram and Huizenga on codimension one subvarieties of the Hilbert scheme.

September 25: Ourmazd (UW-Milwaukee)

Title: Structure and Dynamics from Random Observations

Abstract: At weddings, the bridal photo is taken under bright lights, with the happy couple holding still. Traditionally in science, the “best” observations are those with the largest signal from the most tightly controlled system. Like bridal photos, the results are not always exciting. In a wide range of phenomena – from the dance of proteins during their function, to the breaking of molecular bonds on the femtosecond scale – tight control is neither possible, nor desirable. Modern data-analytical techniques extract far more information from random sightings than usually obtained from set-piece experiments. I will describe on-going efforts to extract structural and dynamical information from noisy, random snapshots. Examples will include YouTube videos, the structure and conformations of molecular machines such as the ribosome, and the ultrafast dynamics of bond-breaking in small molecules like nitrogen.

October 9: Igor Mezic (UC Santa Barbara)

Past Colloquia

Spring 2015

Fall 2014

Spring 2014

Fall 2013

Spring 2013

Fall 2012