2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/100795In these notes we address the canonical quantization of the cosmological models which appear as solutions of the low energy effective action of closed bosonic string theory (dilaton models). The analysis is restricted to the quantization of the minisuperspace models given by homogeneous and isotropic cosmological solutions. We study the different conceptual and technical problems arising in the Hamiltonian formulation of these models as a consequence of the presence of the so called Hamiltonian constraint. In particular we address the problem of time in quantum cosmology, the characterization of the symmetry under clock reversls arising from the existence of a Hamiltonian constraint, and the problem of inposing boundary conditions on the space of solutions of the Wheeler-DeWitt equation.Invited article for the book "Trends in General Relativity and Quantum Cosmology", Nova Science Publishers, NY (2005)Mathematical PhysicsGeneral Relativity and Quantum CosmologyHigh Energy Physics - Theorytext