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location Vienna, Austria
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visits member for 2 years
seen Oct 13 at 14:49

Jun
26
awarded  Promoter
May
29
asked Groupoid $C^*$ algebra of product groupoid
May
19
awarded  Constituent
May
19
awarded  Caucus
Jan
27
revised Question regarding the Kolmogorov-Riesz theorem on relatively compact subsets of $L^p(\Omega)$.
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Jan
27
comment Question regarding the Kolmogorov-Riesz theorem on relatively compact subsets of $L^p(\Omega)$.
Martin: Thanks, but I already knew of this article and while it is very nicely written, it doesn't really address my questions.
Jan
26
comment Question regarding the Kolmogorov-Riesz theorem on relatively compact subsets of $L^p(\Omega)$.
Thanks, 5PM! I probably missed it since I was looking for and English version of the second book on the list at the bottom of this page. Strangely, this book only deals with $L^p(\mathbb R^n)$.
Jan
26
revised Question regarding the Kolmogorov-Riesz theorem on relatively compact subsets of $L^p(\Omega)$.
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Jan
26
asked Question regarding the Kolmogorov-Riesz theorem on relatively compact subsets of $L^p(\Omega)$.
Jan
13
comment Verify a given SVD of an operator
Concerning compactness, write $(Ax)(t) = \int_0^1 a(t,s)x(s)\,ds$ with $a(t,s) := \chi_{[0,t]}(s)$. Then $\int_0^1 \int_0^1 |a(t,s)|^2 \,ds\,dt < \infty$, hence $A$ defines a Hilbert-Schmidt operator which is compact (see en.wikipedia.org/wiki/Hilbert-Schmidt_integral_operator)
Jan
13
revised does it have unique fixed point?
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Jan
13
revised does it have unique fixed point?
added 139 characters in body
Jan
13
answered does it have unique fixed point?
Jan
13
revised Proof of the divergence of a monotonically increasing sequence
tex'd the question
Jan
13
suggested suggested edit on Proof of the divergence of a monotonically increasing sequence
Jan
13
answered If $A\leq B$ in the sense of quadratic forms, then must $A^{-1} \geq B^{-1}$?
Jan
3
comment Linear algebra proofs - traces, symmetricity and inversion
Note that you don't need to compute both $(B^{-1}A^{-1})(AB)$ and $(AB)(B^{-1}A^{-1})$ if $A$ and $B$ are matrices (i.e. linear maps on a finite-dimensional vector space), as one of them will suffice in this case.
Jan
2
answered Solution of the Wave Equation, the not so simple direction
Dec
28
comment where is wrong in the sum of series $\frac{1}{3}+\frac{1}{4}\cdot\frac{1}{2!}+\frac{1}{5}\cdot\frac{1}{3!}+\cdots$
Actually, $x(e^x-1)$ integrates to $1/2$, not $-1/2$.
Nov
10
awarded  Enthusiast