Welcome to the Maryland Distinguished Lectures in Algebra and Number Theory! This is an annual lecture series concerning recent developments in Algebra and Number Theory, delivered by the world's foremost experts. It is organized by Thomas Haines.

### 2022 Mark Kisin

### Theme: Arithmetic of abelian varieties and their moduli

**Essential dimension and prismatic cohomology (Colloquium)**

**Essential dimension and prismatic cohomology (Colloquium)**

**Wednesday, December 7 at 3:15pmUniversity of Maryland - Kirwan Hall Rm 3206**

* Abstract:* The smallest number of parameters needed to define an algebraic covering space is called its essential dimension. Questions about this invariant go back to Klein, Kronecker and Hilbert and are related to Hilbert's 13th problem. In this talk, I will give a little history, and then explain a new approach which relies on recent developments in $p$-adic Hodge theory. This is joint work with Benson Farb and Jesse Wolfson.

**Frobenius conjugacy classes attached to abelian varieties**

**Frobenius conjugacy classes attached to abelian varieties**

**Thursday, December 8 at 2:00pmUniversity of Maryland - Kirwan Hall Rm 3206**

** Abstract:** The Mumford-Tate group of an abelian variety $A$ over the complex numbers is an algebraic group $G$, defined in terms of the complex geometry of $A$, more specifically its Hodge structure. If $A$ is defined over a number field $K$, then a remarkable result of Deligne asserts that the ℓ -adic cohomology of $A$ gives rise to a $G$ -valued Galois representation ρ

_{ℓ}:Gal($\bar K/K$)→$G(\mathbb Q_\ell)$. We will show that for a place of good reduction v∤ℓ of A, the conjugacy class of Frobenius ρ

_{ℓ}(Frob

_{v}) does not depend on ℓ. This is joint work with Rong Zhou.

**Heights in the isogeny class of an abelian variety**

**Heights in the isogeny class of an abelian variety****Friday, December 9 at 2:00pmUniversity of Maryland - Kirwan Hall Rm 3206**

* Abstract:* Let $A$ be an abelian variety over $\bar{\mathbb Q}.$ In this talk I will consider the following conjecture of Mocz. Conjecture: Let $c > 0.$ In the isogeny class of $A,$ there are only finitely many isomorphism classes of abelian varieties of height $ c.$ I will sketch a proof of the conjecture when the Mumford-Tate conjecture - which is known in many cases - holds for $A.$ This result should be compared with Faltings' famous theorem, which is about finiteness for abelian varieties defined over a fixed number field. This is joint work with Lucia Mocz.

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**2021 Wei Zhang**

**2021 Wei Zhang**

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**2019 Ngô Bảo Châu**

**2019 Ngô Bảo Châu**

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