Algebra and Algebraic Geometry Seminar Spring 2019

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Revision as of 15:34, 5 February 2019 by Andreic (talk | contribs) (Abstracts)
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The seminar meets on Fridays at 2:25 pm in room B235.

Here is the schedule for the previous semester, for the next semester, and for this semester.

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Spring 2019 Schedule

date speaker title host(s)
January 25 Daniel Smolkin (Utah) Symbolic Powers in Rings of Positive Characteristic Daniel
February 1 Juliette Bruce Asymptotic Syzgies for Products of Projective Spaces Local
February 8 Isabel Vogt (MIT) Low degree points on curves Wanlin and Juliette
February 15 Pavlo Pylyavskyy (U. Minn) Zamolodchikov periodicity and integrability Paul Terwilliger
February 22 Michael Brown (Wisconsin) Chern-Weil theory for matrix factorizations Local
March 1 Shamgar Gurevich (Wisconsin) Harmonic Analysis on GLn over finite fields, and Random Walks Local
March 8 Jay Kopper (UIC) TBD Daniel
March 15 TBD TBD TBD
March 22 No Meeting Spring Break TBD
March 29 Chris Eur (UC Berkeley) TBD Daniel
April 5 TBD TBD TBD
April 12 Eric Canton (Michigan) TBD Michael
April 19 Eloísa Grifo (Michigan) TBD TBD
April 26 TBD TBD TBD
May 3 TBD TBD TBD

Abstracts

Daniel Smolkin

Symbolic Powers in Rings of Positive Characteristic

The n-th power of an ideal is easy to compute, though difficult to describe geometrically. In contrast, symbolic powers of ideals are difficult to compute while having a natural geometric description. In this talk, I will describe how to compare ordinary and symbolic powers of ideals using the techniques of positive-characteristic commutative algebra, especially in toric rings and Hibi rings. This is based on joint work with Javier Carvajal-Rojas, Janet Page, and Kevin Tucker. Graduate students are encouraged to attend!

Juliette Bruce

Title: Asymptotic Syzygies for Products of Projective Spaces

I will discuss results describing the asymptotic syzygies of products of projective space, in the vein of the explicit methods of Ein, Erman, and Lazarsfeld’s non-vanishing results on projective space.

Isabel Vogt

Title: Low degree points on curves

In this talk we will discuss an arithmetic analogue of the gonality of a curve over a number field: the smallest positive integer e such that the points of residue degree bounded by e are infinite. By work of Faltings, Harris--Silverman and Abramovich--Harris, it is well-understood when this invariant is 1, 2, or 3; by work of Debarre--Fahlaoui these criteria do not generalize to e at least 4. We will study this invariant using the auxiliary geometry of a surface containing the curve and devote particular attention to scenarios under which we can guarantee that this invariant is actually equal to the gonality . This is joint work with Geoffrey Smith.

Pavlo Pylyavskyy

Zamolodchikov periodicity and integrability

T-systems are certain discrete dynamical systems associated with quivers. They appear in several different contexts: quantum affine algebras and Yangians, commuting transfer matrices of vertex models, character theory of quantum groups, analytic Bethe ansatz, Wronskian-Casoratian duality in ODE, gauge/string theories, etc. Periodicity of certain T-systems was the main conjecture in the area until it was proven by Keller in 2013 using cluster categories. In this work we completely classify periodic T-systems, which turn out to consist of 5 infinite families and 4 exceptional cases, only one of the infinite families being known previously. We then proceed to classify T-systems that exhibit two forms of integrability: linearization and zero algebraic entropy. All three classifications rely on reduction of the problem to study of commuting Cartan matrices, either of finite or affine types. The finite type classification was obtained by Stembridge in his study of Kazhdan-Lusztig theory for dihedral groups, the other two classifications are new. This is joint work with Pavel Galashin.

Shamgar Gurevich

Harmonic Analysis on GLn over finite fields, and Random Walks

There are many formulas that express interesting properties of a group G in terms of sums over its characters. For evaluating or estimating these sums, one of the most salient quantities to understand is the {\it character ratio}:

$$ trace(\rho(g))/dim(\rho), $$

for an irreducible representation $\rho$ of G and an element g of G. For example, Diaconis and Shahshahani stated a formula of this type for analyzing G-biinvariant random walks on G. It turns out that, for classical groups G over finite fields (which provide most examples of finite simple groups), there is a natural invariant of representations that provides strong information on the character ratio. We call this invariant {\it rank}. This talk will discuss the notion of rank for GLn over finite fields, and apply the results to random walks. This is joint work with Roger Howe (Yale and Texas AM).