The distribution of the cokernel of a random p-adic matrix

Speaker: 

Myungjun Yu

Institution: 

Yonsei University

Time: 

Thursday, January 23, 2025 - 3:00pm to 4:00pm

Location: 

RH 306

The cokernel of a random p-adic matrix can be used to study the distribution of objects that arise naturally in number theory. For example, Cohen and Lenstra suggested a conjectural distribution of the p-parts of the ideal class groups of imaginary quadratic fields. Friedman and Washington proved that the distribution of the cokernel of a random p-adic matrix is the same as the Cohen–Lenstra distribution. Recently, Wood generalized the result of Friedman–Washington by considering a far more general class of measure on p-adic matrices. In this talk, we explain a further generalization of Wood’s work. This is joint work with Dong Yeap Kang and Jungin Lee.

Erdos-Kac type central limit theorem for randomly selected ideals in a Dedekind domain

Speaker: 

Michael Cranston

Institution: 

UCI

Time: 

Tuesday, January 21, 2025 - 3:00pm to 4:00pm

Location: 

RH 306

Using the Dedekind zeta function, one can randomly select an ideal in a Dedekind domain. Then the factorization of the randomly selected ideal into a product of prime ideals has very nice statistical properties. Using these properties one can examine the number of distinct prime ideals there are in the factorization and prove a central limit theorem as a certain parameter tends to one. This talk is based on joint work with E. Hsu.

The arithmetic dynamics of the pentagram map

Speaker: 

Max Weinreich

Institution: 

Harvard University

Time: 

Thursday, December 5, 2024 - 3:00pm to 4:00pm

Location: 

Zoom: https://uci.zoom.us/j/91741672832

In this talk, we study arithmetic properties of the pentagram map, a dynamical system on convex polygons in the real projective plane. The map sends a polygon to the shape formed by intersecting certain diagonals. This simple operation turns out to define a discrete integrable system, meaning roughly that it can be viewed as a translation map on a family of tori. We show that the pentagram map’s first or second iterate is birational to a translation on a family of Jacobian varieties of algebraic curves. In work in progress, we explore the question of which pentagram-like maps are integrable vs. chaotic. 

Reciprocity Laws and Congruences in Number Theory

Speaker: 

Heejong Lee

Institution: 

Purdue University

Time: 

Thursday, November 7, 2024 - 3:00pm to 4:00pm

Location: 

Zoom: https://uci.zoom.us/j/98066115065

Gauss's quadratic reciprocity law has been extensively generalized in multiple directions within number theory. This talk will begin with explicit examples of reciprocity laws, including an interpretation of the proof of Fermat’s Last Theorem by Wiles and Taylor-Wiles as a consequence of a reciprocity law. As part of this discussion, I will introduce modular forms, elliptic curves, and Galois representations, leading to an overview of the Langlands reciprocity. I will then discuss the role of congruences in the study of reciprocity laws, with a particular focus on the Serre weight conjectures. I will conclude by outlining the proof of the Serre weight conjectures for GSp4. This is partly based on joint work with Daniel Le and Bao Le Hung.

Uniform bounds on Sylvester-Gallai type configurations of polynomials

Speaker: 

Akash Sengupta

Institution: 

University of Waterloo

Time: 

Thursday, October 17, 2024 - 3:00pm to 4:00pm

Host: 

Location: 

Zoom: https://uci.zoom.us/j/91029256231

The classical Sylvester-Gallai theorem says that if a finite set of points in the Euclidean plane has the property that the line joining any two points contains a third point from the set, then all the points must be collinear. More generally, a Sylvester-Gallai type configuration is a finite set of geometric objects with certain "local" dependencies. A remarkable phenomenon is that the local constraints give rise to global dimension bounds for linear SG-type configurations, and such results have found far reaching applications to complexity theory and coding theory.

In this talk we will discuss non-linear generalizations of SG-type configurations which consist of polynomials. We will discuss how the commutative-algebraic principle of Stillman uniformity can shed light on low dimensionality of SG-configurations. I’ll talk about recent progress showing that these non-linear SG-type configurations are indeed low-dimensional as conjectured by Gupta. This is based on joint work with R. Oliveira.

Primitive elements in number fields and Diophantine avoidance

Speaker: 

Sehun Jeong

Institution: 

Claremont Graduate University

Time: 

Thursday, October 10, 2024 - 3:00pm to 4:00pm

Location: 

RH 306

The famous primitive element theorem states that every number field K is of the form Q(a) for some element a in K, called a primitive element. In fact, it is clear from the proof of this theorem that not only there are infinitely many such primitive elements in K, but in fact most elements in K are primitive. This observation raises the question about finding a primitive element of small “size”, where the standard way of measuring size is with the use of a height function. We discuss some conjectures and known results in this direction, as well as some of our recent work on a variation of this problem which includes some additional avoidance conditions. Joint work with Lenny Fukshansky at Claremont McKenna College.

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