mpiktas
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 Feb 19 awarded Popular Question Dec 14 awarded Yearling Dec 14 awarded Yearling Dec 9 awarded Caucus Sep 30 awarded Explainer Jul 2 awarded Curious Dec 14 awarded Yearling Oct 5 comment Dual space of $C_b(X)$ I would try to get this book: books.google.lt/books/about/…, Oct 5 comment A problem about the quadratic form $x^TAx=0$. Usually it is assumed that matrix $A$ is symmetric when we are talking about the quadratic forms. For symmetric matrices the statement holds. Oct 5 comment Solving system of linear eqaution in special cases Others pointed out that $A=ee^T-2I$, I just wanted to mention that this kind of matrix looks like Householder transformation which is well known and even was named among 10 top algorithms of 20th century. Oct 5 comment A problem about the matrix equation $a^{\sf T}A_1a=0$. @Wei-ChengLiu if quadratic form $a^TBa=0$ then $B=0$. We can write any symmetric matrix as $B=P^TDP$, where $D$ is the diagonal matrix. Then $a^TBa=0$ for all $a$ is equivalent to $a^TDa=0$ for all $a$ and then it is clear that $D=0$. The comment of egreg applies to my older version of the answer, where I made some incorrect claims. Oct 4 comment A problem about the matrix equation $a^{\sf T}A_1a=0$. I've removed the offending statement. We can show that $a^T(\alpha A_1+\beta A_1^T)a=0$ for all $a$ and all $\alpha$ and $\beta$, but only for $\alpha=\beta=1$ the matrix $\alpha A_1+\beta A_1^T$ is symmetric and we can invoke the quadratic form property. Oct 4 revised A problem about the matrix equation $a^{\sf T}A_1a=0$. remove the incorrect statement Oct 4 answered A problem about the matrix equation $a^{\sf T}A_1a=0$. May 8 awarded Caucus Jan 10 comment Example of atlas for sequence space @JacobSchlather, yes, open is desirable. But any example would do. Jan 10 asked Example of atlas for sequence space Jan 9 comment Regression with arbitrary norm Have you tried using general optimisation algorithm? Dec 20 accepted Given collection of sets how to turn it to collection of disjoint sets? Dec 20 revised Given collection of sets how to turn it to collection of disjoint sets? clarify the question