Constantin Shramov: On tetragonal construction of R.Donagi
The tetragonal construction of R.Donagi relates to an unramified double cover C' to C over a tetragonal curve C two other double covers of this kind such that all three corresponding Prym varieties are isomorphic. Moreover, there is a conjecture that, roughly speaking, all isomorphisms of Prym varieties arise from this construction. I'll survey the known results on this conjecture and give a (partial) interpretation of the tetragonal construction in terms of threefold birational geometry.