Jonas Meyer
Reputation
37,559
392/400 score
 1d awarded elementary-set-theory May 2 awarded Enlightened May 2 awarded Nice Answer Apr 29 awarded Nice Answer Apr 1 awarded Good Answer Mar 19 awarded Nice Answer Feb 15 comment weak sequential continuity of linear operators @Svetoslav: Unboundedness of T implies that for each $M>0$ there exists x with norm 1 such that $\|Tx\|>M$. Thus for each positive integer n take $y_n$ with norm 1 such that $\|Ty_n\|>n^2$, and take $x_n=\frac1n y_n$. Feb 15 awarded Enlightened Feb 15 awarded Nice Answer Jan 31 comment Example of operator with spectrum equal to $\mathbb{C}$? You have examples for 2 & 3? If so, could you take a direct sum of those? Jan 30 awarded Necromancer Jan 28 awarded Nice Answer Jan 27 awarded Guru Jan 23 comment Why does the Gram-Schmidt procedure divide by 0 on a linearly dependent lists of vectors? @ihadanny: It is 0 because it is a vector in the span of the $e_i$s whose inner product with each $e_i$ is 0. Jan 22 awarded Good Answer Jan 15 awarded Nice Answer Jan 6 awarded Nice Answer Jan 3 reviewed Close why don't standard analysis texts relax the injectivity requirement of the multivariable change of variables theorem? Jan 3 comment $\lim_{x\to c} f(x)=l \implies f(x)$ is defined in a neighbourhood $c$? It depends on context not given. Sometimes yes it would imply that by the definition. Jan 3 reviewed Close $\left (1+\frac{a}{b} \right) \left(1+\frac{b}{c} \right) \left(1+\frac{c}{a} \right) \geq 2 \left ( 1+\frac{a+b+c}{\sqrt[3]{abc}} \right).$