Singular divisors and syzygies of polarized abelian threefolds

We provide numerical conditions for a polarized abelian threefold $(A,L)$ to have simple syzygies, in terms of property $(N_p)$ and the vanishing of Koszul cohomology groups $K_{p,1}$. We rely on a reduction method of Lazarsfeld-Pareschi-Popa, convex geometry of Newton-Okounkov bodies, inversion of adjunction techniques from work on Fujita's conjecture, and the use of differentiation by Ein-Lazarsfeld-Nakamye. As a by-product, we construct effective divisors in any ample class of high self-intersetion, whose singularities are all concentrated on an abelian subvariety. This can be seen as the dual picture considered by Ein-Lazarsfeld for theta divisors.