Moduli spaces of irreducible symplectic manifolds
We study the moduli spaces of polarised irreducible symplectic manifolds. By a comparison with locally symmetric varieties of orthogonal type of dimension 20, we show that the moduli space of 2d polarised (split type) symplectic manifolds which are deformation equivalent to degree 2 Hilbert schemes of a K3 surface is of general type if d is at least 12.
To resolve some geometric problems we give a new, clear, formulation of Siegel's formula for the number of representationс natural numbers by positive definite quadratic forms of odd rank. It may be expressed either in terms of Zagier L-functions or in terms of the H.~Cohen numbers.