2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/198169The evolutions of linear structures in a spatially homogeneous and isotropic world model are characterized by some conserved quantities: the amplitude of gravitational wave is conserved in the super-horizon scale, the perturbed three-space curvature in the comoving gauge is conserved in the super-sound-horizon scale, and the angular momentum of rotational perturbation is generally conserved.4 pages, no figure, Proceedings of The 2nd Seoul Workshop on Gravitation and CosmologyAstrophysicsGeneral Relativity and Quantum Cosmologytext