2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/147669The authors have introduced recently a ``microcanonical functional integral" which yields directly the density of states as a function of energy. The phase of the functional integral is Jacobi's action, the extrema of which are classical solutions at a given energy. This approach is general but is especially well suited to gravitating systems because for them the total energy can be fixed simply as a boundary condition on the gravitational field. In this paper, however, we ignore gravity and illustrate the use of Jacobi's action by computing the density of states for a nonrelativistic harmonic oscillator. (Festschrift for Dieter Brill)10 pages, plain tex. (This replaces the previous version which consisted of less than half of the manuscript.)General Relativity and Quantum CosmologyHigh Energy Physics - Theorytext