Abstract. We relate the m-truncated Kronecker products of symmetric functions to the semi-invariant rings of a family of quiver representations. We find cluster algebra structures for these semi-invariant rings when m = 2. Each g-vector cone G l of these cluster algebras controls the 2-truncated Kronecker products for all symmetric functions of degree no greater than l. As a consequence, each relevant Kronecker coefficient is the difference of the number of the lattice points inside two rational polytopes. We also give explicit description of all G l 's. As an application, we compute some invariant rings.
IntroductionGiven a partition λ of n, let S λ be the associated irreducible complex representation of the symmetric group S n . The Kronecker coefficients g λ µ,ν are the tensor product multiplicities:To determine these coefficients and understand their properties has been one of the major problems in combinatorics and representation theory for nearly a century. People are particularly interested in finding combinatorial interpretation for these coefficients. They hope that Kronecker coefficients count some combinatorial objects, eg., lattice points in polytopes. More recently, the interest in computing Kronecker coefficients has intensified in connection with Geometric Complexity Theory [23], pioneered as an approach to the P vs. NP problem. Despite of a large body of work, those coefficients remain very mysterious. The complete solution of analogous problems for the general linear groups GL n certainly bring new hope to this old problem. The tensor multiplicities of irreducible representations of GL n , known as Littlewood-Richardson coefficients, can be computed by the Littlewood-Richardson rule. According to , they are counted by the lattice points in the so-called hive polytopes. Similar results were also obtained by 4] via an invariant-theoretic approach. The link between these two approachs was established in [10] through Fomin-Zelevinsky's cluster algebras [13,1,14] and their quiver with potential models [5,6]. In this paper, we use the similar ideas in [3,10] to study the Kronecker coefficients.2010 Mathematics Subject Classification. Primary 20C30, 13F60; Secondary 16G20, 13A50, 52B20.