Orbital Degeneracy Loci

I will give an introduction to orbital degeneracy loci, a general construction of varieties generalizing zero loci of sections of vector bundles and degeneracy loci of morphisms. The main ingredient is the orbit structure of certain representations of complex Lie groups. As a sample of applications, I will explain how to construct an abelian surface from a skew-symmetric three-form, in the spirit of the classical construction of an elliptic curve from a cubic form.