Bourbaki

Proposition 11 (Weyl Inequalities)

Tag 02X4, permanent. Cite it as [Bourbaki, Tag 02X4].

Théories spectrales, chapter IV, § 1. Opérateurs compacts sur un espace hilbertien

Let G be a Hilbert space and v∈Lc(F;G)v\in \mathscr{L}^c(F; G). Let g:R+→[−∞,+∞[g:\mathbf{R}_+\rightarrow [-\infty ,+\infty [ be an increasing function such that the function g∘g\circ exp is convex. We have

∑i=0ng(αi(v∘u))⩽∑i=0ng(αi(v)αi(u)) \sum_{i=0}^ng(\alpha_i(v\circ u))\leqslant \sum_{i=0}^ng(\alpha_i(v)\alpha_i(u))

for all n∈IE∩IFn\in I_E\cap I_F.

Put I=[−∞,+∞[I = [-\infty ,+\infty [ and f=g∘f=g\circ exp. We may apply Lemma 5 with

ai=a_i= log(αi(v∘u)\alpha_i(v\circ u))∈I,bi=\in I,b_i= log(αi(v)αi(u)\alpha_i(v)\alpha_i(u))∈I\in I

and ϱi=1\varrho_i= 1 for 0⩽i⩽n0\leqslant i\leqslant n, since

∑i=0jai=\sum_{i=0}^ja_i= log(∏i=0jαi(v∘u))⩽(\prod_{i=0}^j\alpha_i(v\circ u))\leqslant log(∏i=0jαi(v)αi(u))=∑i=0jbi(\prod_{i=0}^j\alpha_i(v)\alpha_i(u))=\sum_{i=0}^jb_i

for 0⩽j⩽n0\leqslant j\leqslant n by the corollary to Prop. 10. Inequality (6) is then the desired conclusion.

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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Machine translation of the English, by gpt-5-6-mini, gpt-5-mini, gpt-5.4, against glossary version 34. Not checked by a person. That model is a cut down version of the one the rest of this language was written by.