{"paper":{"title":"Principal configurations around umbilics of spacelike surfaces in null hypersurfaces of $\\mathbb{R}_1^4$","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"","cross_cats":[],"primary_cat":"math.DG","authors_text":"Didier A. Solis, Matias Navarro, Oscar Palmas","submitted_at":"2019-07-10T00:17:27Z","abstract_excerpt":"We study the principal configurations around an isolated $\\eta$-umbilical point on a generic spacelike surface $S$ immersed in a null hypersurface $M$ of Minkowski space $\\mathbb{R}_1^4$ relative to a well-defined null vector field $\\eta$ orthogonal to the surface $S$. In the particular case of $M$ being a null rotation hypersurface of $\\mathbb{R}_1^4$ we also recover the local Darbouxian principal configurations around that kind of $\\eta$-umbilical points."},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"1907.04465","kind":"arxiv","version":1},"verdict":{"id":null,"model_set":{},"created_at":null,"strongest_claim":"","one_line_summary":"","pipeline_version":null,"weakest_assumption":"","pith_extraction_headline":""},"references":{"count":0,"sample":[],"resolved_work":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","internal_anchors":0},"formal_canon":{"evidence_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}