definition. quadratic form [jadczyk2019notes, 1.9] [ca-0004]

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QuadraticFormQuadraticForm.polar

L∃∀N

Let \(R\) be a commutative ring, \(M\) a \(R\)-module.

An quadratic form \(Q\) over \(M\) is a map \(Q : M \to R\), satisfying:

1. \( Q(a \bullet x) = a * a * Q(x)\) for all \(a \in R, x \in M\).
2. there exists a companion bilinear form \(B : M \to M \to R\), such that \(Q(x + y) = Q(x) + Q(y) + B(x, y)\)

In [jadczyk2019notes], the bilinear form is denoted \(\Phi \), and called the polar form associated with the quadratic form \(Q\), or simply the polar form of \(Q\).