paper

Hidden symmetries and Large N factorisation for permutation invariant matrix observables

arXiv:2112.00498 · doi:10.1007/JHEP08(2022)090

Abstract

Permutation invariant polynomial functions of matrices have previously been studied as the observables in matrix models invariant under , the symmetric group of all permutations of objects. In this paper, the permutation invariant matrix observables (PIMOs) of degree are shown to be in one-to-one correspondence with equivalence classes of elements in the diagrammatic partition algebra . On a 4-dimensional subspace of the 13-parameter space of invariant Gaussian models, there is an enhanced symmetry. At a special point in this subspace, is the simplest invariant action. This is used to define an inner product on the PIMOs which is expressible as a trace of a product of elements in the partition algebra. The diagram algebra is used to prove the large factorisation property of this inner product, which generalizes a familiar large factorisation for inner products of matrix traces invariant under continuous symmetries.

35 pages, 1 figure, V2: typos corrected and refs added, V3: sage code added

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