Alekseevsky, D.Cortés, V.Leistner, T.2023-11-052023-11-052023Revista Matematica Iberoamericana, 2023; 39(3):1105-11410213-22302235-0616https://hdl.handle.net/2440/139844We study the geometry and holonomy of semi-Riemannian, time-like metric cones that are indecomposable, i.e., which do not admit a local decomposition into a semi-Riemannian product. This includes irreducible cones, for which the holonomy can be classified, as well as non-irreducible cones. The latter admit a parallel distribution of null k-planes, and we study the cases k = 1 in detail. We give structure theorems about the base manifold and in the case when the base manifold is Lorentzian, we derive a description of the cone holonomy. This result is obtained by a computation of certain cocycles of indecomposable subalgebras in so(1,n - 1).en©2022 Real Sociedad Matemática Española. Published by EMS Press and licensed under a CC BY 4.0 licenseJournal article10.4171/rmi/13302023-11-05608392Leistner, T. [0000-0002-8837-5215]