Point-counting and topology of algebraic varieties (Siddarth Kannan, UCLA)

A projective algebraic variety X is the zero locus of a collection of homogeneous polynomials, in projective space. When the polynomials have integer coefficients, we can think of the k-valued points X(k) of the variety, for any field k. Now suppose we have two different fields k and k’. How does the behavior of X(k) inform the behavior of X(k’)? It turns out that this is a rich line of inquiry. I will present a particularly pleasing example which relates the topology of the complex-valued points of X with the number of points it has over finite fields.