Category Archives: Hilbert space

Square root lemma

This post is a continuation of Positive operators II, We begin by recalling the main fact proved there, then explain how a classical binomial series leads to a functional calculus for the square root of a positive operator. Corollary  1 … Continue reading

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Positive operators II

This post is a continuation of Positive operators I. The aim here is to explain how the norm of a bounded self–adjoint operator can be expressed in terms of the associated quadratic form. We will first recall the Riesz representation … Continue reading

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Positive operators I

I realized that I have to diverge even more on my way to Krein spaces. We will need square roots of positive operators on real and complex Hilbert spaces, an so there is a need to discuss this subject in … Continue reading

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