CMU Algebra and Combinatorics Seminar

Fall 2016


Meeting Times

Wednesdays, 3–4pm, in Pearce 329.

Webpages from previous semesters:


Date Speaker Affiliation Title
9/7 Ben Salisbury Central Michigan University Rigged Configurations and the Infinity Crystal
9/21 Motohico Mulase University of California, Davis Counting irreducible characters, topology of moduli spaces, and Galois representations
9/28 John Machacek Michigan State University TBD
10/05 Olivia Dumitrescu Central Michigan University Positivity of divisors on blown-up projective spaces
10/12 David C. Murphy Hillsdale College Generalizing Toric Varieties
11/2 Charlotte Ure Michigan State University TBD


Speaker: Ben Salisbury (Central Michigan University)
Title: Rigged Configurations and the Infinity Crystal
Abstract: The infinity crystal models the structure of (one half of) the quantum group (or, quantized universal enveloping algebra) and is built using a complicated algebraic procedure. However, crystals highlight the important combinatorial characteristics of the algebra, and therefore can be modeled using various combinatorial objects. In this talk, the rigged configuration model will be described and some of its important properties will be discussed.

Speaker: Motohico Mulase (University of California, Davis)
Title: Counting irreducible characters, topology of moduli spaces, and Galois representations
Abstract: The talk aims at introducing the audience to the current research frontier on spaces of characters of the fundamental group of a surface. The set of algebraic curves defined over the field of algebraic numbers, on which the absolute Galois group acts, is an example of such a space. We start with explaining a celebrated theorem due to Belyi that connects Galois theory and complex geometry as a motivation. We then illustrate the power of mathematically rigorous "topological quantum field theory" in counting problems on moduli spaces. The talk focuses on the elementary nature of mathematics, sticking to the philosophy that something beautiful must be simple. The talk is based on my joint work with Dr. Dumitrescu, and also our earlier paper with Dr. Safnuk.

Speaker: John Machacek (Michigan State University)
Title: TBD
Abstract: Coming soon.

Speaker: Olivia Dumitrescu (Central Michigan University)
Title: Positivity of divisors on blown-up projective spaces
Abstract: The minimal model program aims at a birational classification of complex algebraic varieties. The classification of surfaces was completed in the beginning of the 20th century by the Italian school of Algebraic Geometry. In the 1980s, minimal model to higher dimension was extended by admitting the presence of suitable singularities. The abundance conjecture and the existence of good models are among the main open problems in the minimal model program. In this talk we study log canonical pairs given by divisors on the blow-up of projective spaces in collections of points in general position. We give a cohomological description of the strict transforms of these divisors in the iterated blow-up along the cycles of the singular locus. Vanishing theorems for the higher cohomologies are used to give a systematic study of semi-ample divisors on these further blown-up spaces. As a consequence, we prove the abundance conjecture for an infinite number of such log canonical pairs, and an explicit construction of good minimal models. This is a joint work with Elisa Postinghel (2015).

Speaker: David C. Murphy (Hillsdale College)
Title: Generalizing Toric Varieties
Abstract: Toric varieties are often introduced and constructed from combinatorial data such as polytopes or cones and fans. In this way, they offer an accessible entry point to algebraic geometry. However, it is important to remember that toric varieties were first viewed as torus embeddings, and it was from this perspective that their classification was derived. It is also from this perspective that a number of attempts to generalize toric varieties and their classification have arisen. In this talk we will discuss toric varieties and one such generalization.

Speaker: Charlotte Ure (Michigan State University)
Title: TBD
Abstract: Coming soon.

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