Quadratic space

Canonical tensors over a nondegenerate quadratic space

Let (𝑉,⟨ β‹…, β‹…βŸ©) be a ^nondegenerate finite-dimensional quadratic space over 𝕂. Consider a basis {𝑣𝑖}𝑛𝑖=1, and let {𝑣′𝑖}𝑛𝑖=1 be the corresponding dual basis. Then the element

πœ”0=π‘›βˆ‘π‘–=1π‘£β€²π‘–βŠ—π‘£π‘–βˆˆπ‘‡2𝑉

is independent of the choice of {𝑣𝑖}𝑛𝑖=1, geoalg and so is its symmetrization

πœ”1=π‘›βˆ‘π‘–=1π‘£β€²π‘–π‘£π‘–βˆˆπ‘†2𝑉

Alternate representation

Let 𝑖 :π‘‰βˆ— →𝑉 be the linear isomorphism induced by ⟨ β‹…, β‹…βŸ© and 𝑗 :End𝕂⁑𝑉 β†’π‘‰βˆ— βŠ—π‘‰ be the canonical isomorphism. Then

πœ”0=((π‘–βŠ—1)βˆ˜π‘—)(id𝑉)


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