2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/100967We prove a positive combinatorial formula for the equivariant class of an orbit closure in the space of representations of an arbitrary quiver of type $A$. Our formula expresses this class as a sum of products of Schubert polynomials indexed by a generalization of the minimal lace diagrams of Knutson, Miller, and Shimozono. The proof is based on the interpolation method of Fehér and Rimányi. We also conjecture a more general formula for the equivariant Grothendieck class of an orbit closure.Final version to appear in Journal of Algebraic GeometryAlgebraic Geometry14N10; 57R45, 05E15, 14M12text