2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/34833A class of non-Markoffian nonunitary models for Newtonian gravity is characterized as following from some rather natural hypotheses. One of such models was previously obtained as the Newtonian limit of a classically stable version of higher derivative gravity. They give rise to a mass threshold around $10^{11}$ proton masses for gravity induced localization, to a breaking of linearity and to the possible identification of thermodynamic and von Neumann entropies.Submitted to Phys. Rev. DGeneral Relativity and Quantum CosmologyHigh Energy Physics - TheoryQuantum Physicstext