2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/33487Fermat-holonomic congruences are proposed as a weaker substitute for the too restrictive class of Born-rigid motions. The definition is expressed as a set of differential equations. Integrability conditions and Cauchy data are studied.19 pagesGeneral Relativity and Quantum Cosmologytext