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Events happening on October 20, 2015

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Oct. 20, 2015 11am (Math 350)	Functional Analysis Jean Renault (University of Orleans, France) X The study of semigroup C-algebras presents new challenges. Among various C-algebras associated to a semigroup, the reduced C-algebra is one of the most tractable. I will show, extending A. Nica's work on quasi-lattice ordered semigroups, how it can be expressed as a groupoid C-algebra. The same techniques can be applied to study C-algebras associated to semigroup actions and to -graphs, where is an arbitrary semigroup. In particular, they give under suitable assumptions the nuclearity of these C-algebras and their ideal structure. Semigroups, inverse semigroups and higher rank graphs Sponsored by the Meyer Fund
Oct. 20, 2015 12:10pm (MATH …	Kempner Jean Renault (Université d'Orléans) X Let be the path space of a Bratteli diagram. The Markov measures are the measures on which are quasi-invariant under the tail equivalence relation and which admit a quasi-product cocycle as Radon-Nikodym derivative. This observation provides a classical identification of the ergodic decomposition of . This will be applied to the study of random walks on groups or on groupoids. This study is a joint ongoing project with T. Giordano. Random walks on Bratteli diagrams
Oct. 20, 2015 1pm (MATH 220)	Grad Algebra/Logic Agnes Szendrei (CU Boulder) The simplest polynomial time algorithm for CSPs: checking local consistency, Part 3
Oct. 20, 2015 2pm (MATH 220)	Keith Kearnes (CU) Tame Congruence Theory
Oct. 20, 2015 2pm (MATH 350)	Lie Theory Richard Green (CU) X Generalized nil-Temperley–Lieb algebras are certain associative algebras defined by generators and relations. The defining relations resemble those of the generalized Temperley–Lieb algebras, but with certain products of generators set equal to zero. I will explain how to use the combinatorics of heaps to define representations of the nil versions of the algebras, and describe some of their properties. Representations of generalized nil-Temperley–Lieb algebras
Oct. 20, 2015 3pm (Math 350)	Jonathan Wise (CU Boulder) X We'll study the general problem of classifying all deformations (of arbitrary orders) of a mathematical object by a commutative ring (and maybe also by a differential graded Lie algebra), culminating in the representability theorems of Artin and Schlessinger. Higher order derivatives and representability

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