Elías García, Joan2025-07-282025-07-282024-01-090008-4395https://hdl.handle.net/2445/222605We characterize the finite codimension sub-k-algebras of $\mathbf{k} \llbracket t \rrbracket$ as the solutions of a computable finite family of higher differential operators. For this end, we establish a duality between such a sub-algebras and the finite codimension $\mathbf{k}$-vector spaces of $\mathbf{k}[u]$, this ring acts on $\mathbf{k} \llbracket t \rrbracket$ by differentiation.15 p.application/pdfengcc-by-nc-sa (c) Joan Elías, 2024http://creativecommons.org/licenses/by-nc-sa/3.0/es/Singularitats (Matemàtica)Anells localsSingularities (Mathematics)Local ringsinfo:eu-repo/semantics/article7450842025-07-28info:eu-repo/semantics/openAccess