= Unimodular intersection pairing
{title2=$L\xrightarrow{\sim}\operatorname{Hom}(L,\mathbb Z)$}
An integral <intersection form> on a finite-rank free <abelian group> $L$ is unimodular if its adjoint $x\mapsto\lambda(x,-)$ is an <isomorphism> to the integral dual. In an integral basis, this is equivalent to the pairing matrix having determinant $1$ or $-1$, not merely nonzero determinant. For example, <projective lines generate a unimodular intersection form> on the <Complex projective plane>, with matrix $(1)$ in its complex <orientation>.
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