Workshop

The idea of a Galois theory of periods comes from an insight of Grothendieck. I shall briefly outline of this (conjectural) theory, then sketch the path which led me from it to the AO conjecture, as well as some paths backward. Principally polarized abelian varieties of dimension  g  are parametrized by the algebraic variety  A_g, those with prescribed extra "symmetries" by special subvarieties of  A_g, and those with maximal symmetry (complex multiplication) by special points. The AO conjecture characterizes special subvarieties of  A_g  by the density of their special points. It has been proven last year, after two decades of collaborative efforts putting together many different areas

I will discuss a program of V. Golyshev and collaborators to develop a theory of motivic gamma functions. These are Mellin transforms of period integrals. They satisfy the same recursive relations as solutions of the Picard Fuchs equation. 

In this talk, I will introduce the famous result by Gangl-Kaneko-Zagier about a family of period polynomial relations among double zeta value of even weight. Then I will generalize their result in various ways, from which we can see the appearance of periods of newforms in low levels. At the end, I will give a generalization of the Eichler-Shimura-Manin correspondence to the case of the space of newforms of level 2 and 3 and a certain period polynomial space

It is conjectured that several graded Lie algebras coming up in different fields of mathematics coincide: the Grothendieck-Teichmueller Lie algebra grt related to the braid group in 3d topology, the double shuffle Lie algebra ds in the theory of multiple zeta values and the Kashiwara-Vergne Lie algebra kv in Lie theory. We are adding one more piece to this puzzle: it turns out that the Kashiwara-Vergne Lie algebra plays an important role in the Goldman-Turaev theory defined in terms of intersections and self-intersections of curves on 2-manifolds. This allows to define the Kashiwara-Vergne problem for surfaces of arbitrary genus. In particular, we focus on the genus one case and discuss the relation between elliptic kv and elliptic grt. The talk is based on a joint work with N. Kawazumi, Y. Kuno and F. Naef

We recall the main results of double shuffle theory: the cyclotomicanalogues of MZVs (of order $N\geq 1$) satisfy a collection of relations arising from the study of their combinatorics, and also from their identifications with periods. The scheme arising from these relations is a torsor Under a prounipotent algebraic group $\mathrm{DMR}_0$.  This is a subgroup of the group $\mathrm{Out}^*$ of invariant tangential outer automorphisms of a free Lie algebra, equipped with an action of $\mu_N$. The Lie algebra $\mathfrak{dmr}_0$ of $\mathrm{DMR}_0$ is a subspace of the Lie algebra $\mathrm{out}^*$, defined by a pair of shuffle relations (Racinet) and containing the Grothendieck-Teichmüller Lie algebra or its analogues(Furusho). We show that the harmonic coproduct may be viewed as an element of a module over $\mathrm{out}^*$, and that $\mathfrak{dmr}_0$ then identifies with the stabilizer Lie algebra of this element. A similar identification concerning $\mathrm{DMR}_0$ enables one to construct a "Betti" version of the harmonic coproduct, and to identify the scheme arising from double shuffle relations as the set of elements of $\mathrm{Out}^*$ taking the harmonic coproduct to its "Betti" version

The category of representations over a quantum group $U_q(g)$ form a braided tensor category that produces an action of the (pure) braid groups on tensor products. Respectively, the category of crystals (which is a limit for q tends to zero) form a coboundary category together with an action of (pure) cacti group on tensor products. The little discs operad is an operad whose space of $n$-ary operations is the Eilenberg-Maclein space of the pure braid groups with $n$ braids. Correspondingly, the real locus of the Deligne-Mumford compactification of the moduli space of stable rational curves with marked points assemble an operad of the Eilenberg-Maclein spaces of pure cacti groups. I will present the detailed description of the latter operad as well as its deformation theory and relationships with the little discs operad, graph complexes and Grothendieck-Teichmuller Lie algebra

Given the interpretation of classical periods as matrix coefficients arising in the comparison between singular and de Rham cohomology of complex algebraic varieties, it is natural to view as a p-adic analogue the comparison between etale, crystalline, and de Rham cohomology of algebraic varieties. We describe some new results and perspectives on p-adic comparison isomorphisms emerging from recent developments in the theory of perfectoid spaces. These include a new direct cohomological realization of the crystalline comparison isomorphism (by Bhatt-Morrow-Scholze), and the discovery of "abstract instances" of comparison isomorphisms corresponding to as-yet-unknown families of motives over Shimura varieties (by Liu-Zhu).

I will discuss some new relationships between iterated p-adic line integrals (Coleman integrals), motivated by the problem of explicitly finding rational points on curves. This is joint work with Netan Dogra

A supercongruence is a congruence between rational numbers modulo a power of a prime. Many supercongruences are known for rational approximations of periods, and in particular for finite truncations of the multiple zeta value series. In this talk, I will explain how the Galois theory of multiple zeta values leads to a Galois theory of supercongruences.