2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/155745We study the properties of a two-body random matrix ensemble for distinguishable spins. We require the ensemble to be invariant under the group of local transformations and analyze a parametrization in terms of the group parameters and the remaining parameters associated with the "entangling" part of the interaction. We then specialize to a spin chain with nearest neighbour interactions and numerically find a new type of quantum phase transition related to the strength of a random external field i.e. the time reversal breaking one body interaction term.15 pages, 6 eps figures, submitted to New J. PhysQuantum Physicstext