Seminars Sorted by Series

In the third talk, I will concentrate on inequalities for linear extensionsof finite posets.  I will start with several inequalities which do have a combinatorial proof.  I will then turn to Stanley's inequality and outline the proof why its defect...

A classical construction associates a Poincare duality algebra to a homogeneous polynomial on a vector space. This construction was used to give a presentation for cohomology rings of complete smooth toric varieties by Khovanskii and Pukhlikov and...

A sequence of nonnegative real numbers $a_1, a_2, \ldots, a_n$, is log-concave if $a_i^2 \geq a_{i-1}a_{i+1}$ for all $i$ ranging from 2 to $n-1$. Examples of log-concave inequalities range from inequalities that are readily provable, such as the...

I will motivate the study of the Schubert variety of a pair of linear spaces via Kempf collapsing of vector bundles. I'll describe equations defining this variety and how this yields a simplicial complex determined by a pair of matroids which...

Lecture Series Framework:  A unifying framework for F1-geometry, tropical schemes and matroid theory. In this series of 3 lectures, I will present a recent approach towards F1-geometry and its links to tropical geometry, matroid theory, Lorentzian...

In this talk, I will describe a new definition, joint with Bivas Khan, for a tropical toric vector bundle on a tropical toric variety. This builds on the tropicalizations of toric vector bundles, and can be used to define tropicalizations of vector...

The moduli space of pointed rational curves has a natural action of the symmetric group permuting the marked points.  In this talk, we will present a combinatorial formula for the induced representation on the cohomology of the moduli space, along...

Multi-variate residues on Grassmannians $G(k,n)$ and moduli spaces $M_{0,n}$ are ubiquitous in the study of scattering amplitudes; they provide a powerful and essential tool. Amenable theories include the biadjoint scalar, NLSM, Yang-Mills, gravity...

For an embedded stable curve over the real numbers we introduce a hyperplane arrangement in the tangent space of the Hilbert scheme. The connected components of its complement are labeled by embeddings of the graph of the stable curve to a compact...

The study of the topology of hyperplane arrangement complements has long been a central part of combinatorial algebraic geometry. I will talk about intersection pairings on the twisted (co)homology for a hyperplane arrangement complement, first...

The second lecture features the nuts and bolts of the invariants from first lecture, which we call foundations. We explain the structure theorem for foundations of ternary matroids, which is rooted in Tutte's homotopy theorem. We show how this...

The theme of the third lecture is the notion of points over F1, the field with one element. Several heuristic computations led to certain expectations on the set of F1-points: for example the Euler characteristic of a smooth projective complex...

A valuation is a finitely additive measure on the class of all convex compact subsets of $R^n$. Over the past two decades, a number of structures has been discovered on the space of translation invariant smooth valuations. Recently, these findings...

Abstract: I will discuss work in progress developing the theory of log prismatic cohomology and related theories using the Cartier-Witt stack.   

Given a family of motives, the de Rham realization (a certain vector bundle with integrable "Gauss-Manin" connection) can be compared to the crystalline realizations for various primes p, but the resulting Frobenius structures cannot be directly...

Let X be a proper, smooth rigid space and G a commutative rigid group. We study the relationship between G-representations of the fundamental group of X and G-Higgs bundles on X. This is joint work with Ben Heuer and Mingjia Zhang.

We develop on a new strategy based on point-set topology, which allows us to produce a purely p-adic statement for the crystallinity properties of rigid flat connections. 

Joint with Michael Groechenig.

Lusztig's theory of character sheaves for connected reductive groups is one of the most important developments in representation theory in the last few decades. In this talk, we will describe a construction which extends this "depth zero" picture to...

Let $E$ be a finite degree extension of $Qp$. Given a mod p representation of the absolute Galois group of E we construct a sheaf on a punctured absolute Banach-Colmez space that should give the first step in the construction of the mod p local...

A theorem of Borel says that any holomorphic map from a complex algebraic variety to a smooth arithmetic variety is automatically an algebraic map. The key ingredient is to show that any holomorphic map from the (poly) punctured disc to the Baily...

Let $f:Y \rightarrow X$ be a finite covering map of complex algebraic varieties. The essential dimension of f is the smallest integer e such that, birationally, f arises as the pullback of a covering $Y^{'} \rightarrow X^{'}$ of dimension e, via a...

The minimal model program for 3-folds has been developed only in characteristics $p \geq 5$. A key difficulty at small primes is that the singularities occurring in the minimal model program need not be Cohen-Macaulay, as they are in characteristic...

I will talk about (very much in progress) joint work with Mark Kisin on a Hodge—Newton style inequality for the mod p Breuil—Kisin modules arising from crystalline Galois representations.

With every bounded prism Bhatt and Scholze associated a cohomology theory of formal p-adic schemes. The prismatic cohomology comes equipped with the Nygaard filtration and the Frobenius endomorphism. The Bhatt-Scholze construction has been advanced...

The recent work of Drinfeld and Bhatt-Lurie led to a new geometric approach to p-adic cohomology theories, analogously to what was done earlier in Hodge theory by Simpson. This stacky perspective gives in particular a new approach to p-adic non...

In joint work in progress with Anschütz and Le Bras we aim to construct a 6-functor formalism for quasicoherent sheaves on the relative Fargues-Fontaine curve over rigid-analytic varieties (and even general v-stacks), providing new insights into the...

In chromatic homotopy theory, an object like the sphere spectrum $S^0$ is studied by means of its "localizations", much as an abelian group can be localized at each prime p.  Remarkably, the "primes" $K(n)$ in the homotopy setting correspond to...

A smooth, oriented n-manifold is called a homotopy sphere if it is homeomorphic, but not necessarily diffeomorphic, to the standard n-sphere. In dimensions $n>4$, one often studies the group Θn of homotopy spheres up to orientation-preserving...

Abstract: Since the original conjectures of Beilinson and Lichtenbaum in the 80s, several versions of motivic cohomology have been introduced and developed, notably by Voevodsky. Most classically, Bloch's higher Chow groups provide the accepted...

Abstract: Multiplier ideals and test ideals are ways to measure singularities in characteristic zero and p > 0 respectively.  In characteristic zero, multiplier ideals are computed by a sufficiently large blowup by comparing the canonical module of...

Abstract: The p-adic Simpson correspondence aims to give a non-abelian generalisation of the Hodge-Tate decomposition. Following an idea of Faltings, it should relate pro-étale vector bundles on smooth rigid spaces over Cp to Higgs bundles. In this...

Abstract: Recently the work of Fargues--Scholze provides a geometrization of the local Langlands conjecture. It is natural to ask if in this context any form of local-global compatibility can be stated/verified. We discuss some expectations and...

Abstract: In recent work with Antieau and Nikolaus we use prismatic cohomology to compute algebraic K-theory of Z/pn and similar rings. Our approach is based on a new description of absolute prismatic cohomology, which can be made completely...

Abstract: Given an étale Zp-local system of rank n on an algebraic variety X, continuous cohomology classes of the group GLn(Zp) give rise to classes in (absolute) étale cohomology of the variety with coefficients in Qp. These characteristic classes...

Abstract: We study prismatic crystals and their cohomology by using q-Higgs modules (= a q-analogue of p-connections). When the base is lying over the q-crystalline prism, they are locally described in terms of q-Higgs modules and the associated...

Abstract: Chromatic homotopy theory relates certain important questions in homotopy theory to the theory of formal groups. 

Recent advancements in p-adic geometry can be thus used to study questions in homotopy theory. I will discuss how this...

Abstract: We will explain how to construct a Kirillov model for Emerton's completed cohomology of the tower of modular curves. The trickiest part is to prove injectivity of this model.  This is joint work with Shanwen Wang.

Abstract: I will discuss the formulation and sketch the proofs of duality theorems for the geometric and arithmetic p-adic pro-étale cohomology of Stein spaces. This is based on a joint work with Pierre Colmez and Sally Gilles.

Abstract: Let p be a prime number. Emerton introduced the p-adically completed cohomology, which admits a representation of some p-adic group and can be thought of as some spaces of p-adic automorphic forms. In this talk, I want to explain that for...

Abstract: For a reductive group $G$, its $B_{d}R^{+}$-affine Grassmannian is defined as the étale (equivalently, v-) sheafification of the presheaf quotient $LG/L^{+}G$ of the $B_{d}R$-loop group $LG$ by the $B_{d}R^{+}$-loop subgroup $L^{+}G$. We...

Abstract: The key principle in Grothendieck's algebraic geometry is that every commutative ring be considered as the ring of functions on some geometric object. Clausen and Scholze have introduced a categorification of algebraic and analytic...

Abstract: I'll give an exposition of the theory of "multiplicative polynomial laws," introduced by Roby, and how (following a suggestion of Scholze) they can be applied to the theory of commutative (flat) group schemes. This talk will feature more...