Norbert
Reputation
91/100 score
 1d comment Every finite-dimensional subspace is one-complemented Good references! 2d comment If $\left( {\begin{array}{*{20}{c}} A & B \\ B & A \\ \end{array}} \right) \ge 0 \Rightarrow A \ge B$ this answer is wrong in so many ways Nov 24 revised Uniform convergence of series $\sum\limits_{n=2}^\infty\frac{\sin n x}{n\log n}$ deleted 69 characters in body Nov 21 revised Weighted $L_1$ norm added 115 characters in body Nov 21 awarded functional-analysis Nov 20 comment Dual space of arbitrary direct sum is the direct sum of dual spaces This notation is used to unify the zoo of norms on the sums of Banach spaces. The generic one is $\bigoplus_p$ where $1\leq p\leq+\infty$. Nov 20 awarded Nice Answer Nov 20 answered Dual space of arbitrary direct sum is the direct sum of dual spaces Nov 17 comment Is every Banach space densely embedded in a Hilbert space? Is this embedding assumed to be linear? Nov 16 answered Weighted $L_1$ norm Nov 16 comment Weighted $L_1$ norm Do you assume that $w_i>0$ ? Nov 15 awarded Yearling Nov 15 comment Norm of matrix in $M_2(\mathbb{C})$ as operator on $\ell_p^2$ Evaluation of operator norm between finite-dimensional $\ell_p$-spaces is NP complete. Don't hope to get an explicit formula. Nov 12 comment Ranges of projection operators @TomekKania Why don't you post your counterexample? Nov 12 comment Integral $\int_{-1}^1\frac1x\sqrt{\frac{1+x}{1-x}}\ln\left(\frac{2\,x^2+2\,x+1}{2\,x^2-2\,x+1}\right) \ \mathrm dx$ @0.5772156649... Ok, I read that. Now please read the whole comments thread and than this which, clearly was ''dedicated'' to Cleo Nov 9 comment Prove an equality ($L^P$ spaces) I added an alternative proof Nov 9 revised Prove an equality ($L^P$ spaces) added 1705 characters in body Nov 9 answered Prove an equality ($L^P$ spaces) Nov 8 comment Proving that closed (and open) balls are convex I proved this $\phantom{}$ Nov 6 comment How to find the center of a sphere so that it touches the unit sphere on some predefined subset of unit sphere. What is $S_X$?$\phantom{}$