AbstractBuilding on work of Oh-Thomas, I will introduce invariants for counting surfaces on Calabi-Yau fourfolds. In a family, they are deformation invariant along Hodge loci. If non-zero, the variational Hodge conjecture for the family under consideration holds. Time permitting, I will discuss different compactifications of the moduli spaces of surfaces involved, and some (conjectural) relatio...
AbstractWe discuss the enumerative geometry of moduli spaces of sheaves with 2 dimensional support on K3 surfaces in K3-fibered threefolds and 4 folds. The reason to study such specific geometric setups is that these often provide computable invariants which govern deep information about geometry of moduli spaces of solutions to N=2 Super Yang-Mills theory on K3 surfaces, when the base surface ...