Deformations and moduli of irregular canonical covers with K2=4pg−8
In this talk, we study the moduli of irregular surfaces of general type with at worst canonical singularities satisfying K2=4pg−8, for any even integer pg≥4. We carry out our study by investigating the deformations of the canonical morphism φ:X→PN that is a quadruple Galois cover of a smooth surface of minimal degree. As a result, we show the existence of infinitely many moduli spaces, satisfying the strict Beauville inequality pg>2q−4, with an irreducible component that has a proper "quadruple" sublocus where the degree of the canonical morphism jumps up. The existence of jumping subloci is in contrast with the moduli of surfaces with K2=2pg−4, studied by Horikawa. These irreducible moduli components with a jumping sublocus also present a similarity and a difference to the moduli of curves of genus g≥3, for, like in the case of curves, the degree of the canonical morphism goes down outside a closed sublocus but, unlike in the case of curves, it is never birational.