2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/35511When space-time is assumed to be non-Riemannian the minimal coupling procedure (MCP) is not compatible, in general, with minimal action principle (MAP). This means that the equations gotten by applying MCP to the Euler-Lagrange equations of a Lagrangian $\cal L$ do not coincide with the Euler-Lagrange equations of the Lagrangian obtained by applying MCP to $\cal L$. Such compatibility can be restored if the space-time admits a connection-compatible volume element. We show how these concepts can alter qualitatively the predictions of the Einstein-Cartan theory of gravity.LaTeX 6 pages, (This Essay was awarded a Honorable Mention for 1994 by the Gravity Research Foundation), preprint IFUSP/P-1112General Relativity and Quantum CosmologyHigh Energy Physics - Theorytext