Bourbaki

Corollary 7

Tag 076E, permanent. Cite it as [Bourbaki, Tag 076E].

Algebra, chapter VII, § 5. Endomorphisms of vector spaces

We have det⁡(Tr⁡(ui+j)0≤i,j≤n)=dis⁡(χu)\det(\operatorname{Tr}(u^{i+j})_{0 \leq i,j \leq n}) = \operatorname{dis}(\chi_u).

Let D be the Vandermonde matrix (αij)1≤i,j≤n(\alpha_i^j)_{1 \leq i,j \leq n}. Then (III, p. 532, formula (29)):

det⁡(D)2=∏i<j(aj−αi)2=dis⁡(χu). \det(D)^2 = \prod_{i < j} (a_j - \alpha_i)^2 = \operatorname{dis}(\chi_u).

Moreover, the (i,j)(i, j)-th entry of D⋅′DD \cdot 'D is ∑kαki+j−2=Tr⁡(ui+j−2)\sum_k \alpha_k^{i+j-2} = \operatorname{Tr}(u^{i+j-2}), and the corollary follows.

Bourbaki puts the proof directly after the statement, so what is above is the statement and its proof together.

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Cites

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Transcribed from the printed edition, 2003, Springer. Not translated.