Massey products on cycles of projective lines and trigonometric solutions of the Yang-Baxter equations

Abstract

We show that a nondegenerate unitary solution $r(u,v)$ of the associative Yang-Baxter equation (AYBE) for $\Mat(N,\C)$ (see math.AG/0008156) with the Laurent series at $u=0$ of the form $r(u,v)=\frac{1\ot 1}{u}+r_0(v)+...$ satisfies the quantum Yang-Baxter equation, provided the projection of $r_0(v)$ to traceless matrices has a period. We classify all such solutions of the AYBE extending the work of Schedler math.QA/0212258. We also characterize solutions coming from triple Massey products in the derived category of coherent sheaves on cycles of projective lines.

32 pages, v3: added the proof of the fact that all nondegenerate unitary solutions of the AYBE depending only on spectral parameter are rational; v4: small typos corrected