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 Jan 27 awarded Nice Question 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 $L^p(\Omega)$. added 6 characters in body 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 $L^p(\Omega)$. added 48 characters in body 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? added 139 characters in body 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 approved 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 $-1/2$.