# School of Mathematics

## Time quasi-periodic gravity water waves in finite depth

## Topological and arithmetic intersection numbers attached to real quadratic cycles

Abstract: I will discuss a recent conjecture formulated in an ongoing project with Jan Vonk relating the intersection numbers of one-dimensional topological cycles on certain Shimura curves to the arithmetic intersections of associated real multiplication points on the Drinfeld p-adic upper half-plane. Numerical experiments carried out with Vonk and James Rickards supporting the conjecture will be described.

## Pseudorandom generators for unordered branching programs

We present an explicit pseudorandom generator with seed length $\tilde{O}((\log n)^{w+1})$ for read-once, oblivious, width $w$ branching programs that can read their input bits in any order. This improves upon the work of Impaggliazzo, Meka and Zuckerman where they required seed length $n^{1/2+o(1)}$.

## Higher Hida theory

## Modularity lifting theorems for non-regular symplectic representations

Abstract: We prove an ordinary modularity lifting theorem for certain non-regular 4-dimensional symplectic representations over totally real fields. The argument uses both higher Hida theory and the Calegari-Geraghty version of the Taylor-Wiles method. We also present some applications of these theorems to abelian surfaces. (Joint work with F. Calegari, T. Gee, and V. Pilloni.)

## Potential automorphy of some compatible systems over CM fields

## Automorphy of mod 3 representations over CM fields

Abstract: Wiles' work on modularity of elliptic curves over the rationals, used as a starting point that odd, irreducible represenations $G_Q \rightarrow GL_2 (F_3)$ arise from cohomological cusp forms (i.e. new forms of weight $K \geq 2$).

## Language edit distance, $(\min,+)$-matrix multiplication & beyond

The language edit distance is a significant generalization of two basic problems in computer science: parsing and string edit distance computation. Given any context free grammar, it computes the minimum number of insertions, deletions and substitutions required to convert a given input string into a valid member of the language. In 1972, Aho and Peterson gave a dynamic programming algorithm that solves this problem in time cubic in the string length. Despite its vast number of applications, in forty years there has been no improvement over this running time.