Bourbaki

Remark 4

Tag 00O7, permanent. Cite it as [Bourbaki, Tag 00O7].

Algebra, VIII, p. 420, § 21. Linear Representations of Finite Groups

Let HH be a subgroup of GG of cardinal mm. The isomorphism φ\varphi restricts to an isomorphism from μm(K)\mu_m(K) to μm(K′)\mu_m(K') and, consequently, a ring isomorphism φH\varphi_H from RK(H)R_K(H) to RK′(H)R_{K'}(H). The following diagrams commute:

RK(G)→Res⁡HGRK(H)↓φG↓φHRK′(G)→Res⁡HG′RK′(H), \begin{array}{ccc} R_K(G) & \xrightarrow{\operatorname{Res}_H^G} & R_K(H) \\ \downarrow \varphi_G & & \downarrow \varphi_H \\ R_{K'}(G) & \xrightarrow{\operatorname{Res}_H^{G'}} & R_{K'}(H) , \end{array}
RK(H)→Ind⁡HGRK(G)↓φH↓φGRK′(H)→Ind⁡HG′RK′(G). \begin{array}{ccc} R_K(H) & \xrightarrow{\operatorname{Ind}_H^G} & R_K(G) \\ \downarrow \varphi_H & & \downarrow \varphi_G \\ R_{K'}(H) & \xrightarrow{\operatorname{Ind}_H^{G'}} & R_{K'}(G) . \end{array}

The commutativity of the first diagram is obvious, and that of the second follows from it using Frobenius reciprocity and formula (47).

Bourbaki sets the proof directly after the statement, and the corpus does not separate them, so what is above is the statement and its proof together.

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Transcribed from the printed edition, 2023, Springer Nature. Not translated.