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7 exercise(s) shown, 0 hidden
Apr 20'25
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Find an explicit orthonormal basis of the separable Hilbert space

[[math]] H=L^2[0,1] [[/math]]

by applying the Gram-Schmidt procedure to the polynomials [math]f_n=x^n[/math], with [math]n\in\mathbb N[/math].

Apr 20'25
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Develop a theory of projections, isometries and symmetries inside [math]B(H)[/math], notably by examining the validity of the formula

[[math]] \lim_{n\to\infty}(PQ)^n=P\wedge Q [[/math]]

when talking about projections, and also by taking into account the fact that

[[math]] UU^*=1\iff U^*U=1 [[/math]]

does not necessarily hold in infinite dimensions, when talking about isometries.

Apr 20'25
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Prove that for the usual matrices [math]A,B\in M_N(\mathbb C)[/math] we have

[[math]] \sigma^+(AB)=\sigma^+(BA) [[/math]]

where [math]\sigma^+[/math] denotes the set of eigenvalues, taken with multiplicities.

Apr 20'25
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Prove that an operator [math]T\in B(H)[/math] satisfies the condition

[[math]] \lt Tx,x \gt \geq0 [[/math]]

for any [math]x\in H[/math] precisely when it is positive in our sense, [math]\sigma(T)\subset[0,\infty)[/math].

Apr 20'25
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Clarify, with examples and counterexamples, the relation between the eigenvalues of an operator [math]T\in B(H)[/math], and its spectrum [math]\sigma(T)\subset\mathbb C[/math].

Apr 20'25
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Assuming that an operator [math]T\in B(H)[/math] is normal, [math]TT^*=T^*T[/math], apply the Gelfand theorem to the [math]C^*[/math]-algebra that it generates

[[math]] \lt T \gt \subset B(H) [[/math]]

in order to deduce a diagonalization theorem for [math]T[/math].

Apr 20'25
[math] \newcommand{\mathds}{\mathbb}[/math]

Develop a theory of noncommutative geometry, by formally writing any [math]C^*[/math]-algebra, not necessarily commutative, as

[[math]] A=C(X) [[/math]]

with [math]X[/math] being a “compact quantum space”, and report on what you found.