Source: wikibot/arf-invariant
= Arf invariant
{wiki=Arf_invariant}
The Arf invariant is a topological invariant associated with a smooth, oriented manifold, particularly in the context of differential topology and algebraic topology. It is especially relevant in the study of 4-manifolds and can be used to classify certain types of manifolds. The Arf invariant can be defined for a non-singular quadratic form over the field of integers modulo 2 (denoted as \\(\\mathbb\{Z\}/2\\mathbb\{Z\}\\)).