Lagrangian cell complexes and Markov numbers

Jonny Evans
University College London
September 20, 2016
Joint work with Ivan Smith. Let p be a positive integer. Take the quotient of a 2-disc by the equivalence relation which identifies two boundary points if the boundary arc connecting them subtends an angle which is an integer multiple of ($2 \pi / p$). We call the resulting cell complex a '$p$-pinwheel'. We will discuss constraints on Lagrangian embeddings of pinwheels. In particular, we will see that a p-pinwheel admits a Lagrangian embedding in $CP^2$ if and only if $p$ is a Markov number.

Algebraic geometric codes and their applications

Gil Cohen
Princeton University
September 20, 2016
In 1975 Goppa suggested a general method for constructing error correcting codes based on algebraic geometry. In a long line of research such codes were constructed, constituting as a precious example of a construction that beats the probabilistic method (namely, the Gilbert-Varshamov bound). In this talk we give a brief introduction to algebraic geometric codes, and present applications to small-bias sets and, if time permits, also to hitting set generators for low degree polynomials. No prior knowledge in algebraic geometry is assumed.