Resumen: In this article we study the delta invariant of reduced curve germs via topological techniques. We describe an explicit connection between the delta invariant of a curve embedded in a rational singularity and the topological Poincaré series of the ambient surface. This connection is established by using another formula expressing the delta invariant as ‘periodic constants’ of the Poincaré series associated with the abstract curve and a ‘twisted’ duality developed for the Poincaré series of the ambient space. Idioma: Inglés DOI: 10.1007/s40687-024-00457-8 Año: 2024 Publicado en: Research in Mathematical Sciences 11, 3 (2024), 47 [18 pp.] ISSN: 2522-0144 Factor impacto JCR: 1.2 (2024) Categ. JCR: MATHEMATICS rank: 84 / 483 = 0.174 (2024) - Q1 - T1 Factor impacto SCIMAGO: 0.956 - Applied Mathematics (Q1) - Theoretical Computer Science (Q1) - Mathematics (miscellaneous) (Q1) - Computational Mathematics (Q1)