 Algebraic concordance group over a field

Let $F$ be a field of characteristic different from two. In the convention corresponding to isometric structures with no eigenvalues $\pm 1$, use finite even-sized matrices $V$ for which both $V-V^T$ and $V+V^T$ are nonsingular. Their Witt group under direct sum, with metabolic Seifert forms set to zero, is the algebraic concordance group over $F$. Thus $V$ and $W$ define the same class when $V\oplus (-W)$ is metabolic.^[ref]

Invertibility of $V$ itself is a separate condition: in this Witt classification one can choose invertible representatives before converting to isometric structures. For $F=\mathbb{Q}$, integral Seifert matrices of knots satisfy the symmetric and skew nondegeneracy conditions, and define rational algebraic-concordance classes. Extension to $\mathbb{R}$ detects signature information, while extension to p-adic fields can retain torsion subgroup information invisible over $\mathbb{R}$.