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Dec
22
comment consider the normed linear spaces $(\mathcal C[0,1], ||.|| _i)$.what can you conclude about the correspoding open unit balls?
math.stackexchange.com/questions/66029/…
Dec
20
awarded  Nice Answer
Dec
18
revised group operations are smooth in $\text{SL}(n, \mathbb{R})$
added 273 characters in body
Dec
18
answered group operations are smooth in $\text{SL}(n, \mathbb{R})$
Dec
16
comment If $I$ is a closed ideal in a C*-algebra $A$ and $J$ is a closed ideal in $I$ then $J$ is an ideal of $A$
How does $ab \in J$ follow from $ab^{1/2}\in I$? We have $b \in J^+$ but as far as I can tell there is no reason why we should also have $b^{1/2}$.
Dec
16
comment A concave positive function on $[1,\infty)$ is uniformly continuous
@user161825 It's a pity that there is no badge for it.
Dec
16
comment If $I$ is a closed ideal in a C*-algebra $A$ and $J$ is a closed ideal in $I$ then $J$ is an ideal of $A$
I don't understand your proof. Yes, for all $b \in J^+$ we also have $b \in I$ and therefore $ab,ba \in I$. But it doesn't follow that $ab^{1/2}$ or $ab$ are in $J$.
Dec
9
awarded  Popular Question
Dec
9
revised Minkowski type inequality in Banach algebras
It's likely to be a Cauchy-Schwarz type inequality since Cauchy died in 1857 and Schwartz was born in 1915.
Dec
9
comment Minkowski type inequality in Banach algebras
Thanks. Now what about changing Cauchy-Schwartz to Cauchy-Schwarz?
Dec
9
comment Minkowski type inequality in Banach algebras
Yeah, just figured it out this very second. Duh. 6 minutes too late.
Dec
9
comment Minkowski type inequality in Banach algebras
Thank you for your comment, I understand. I have one question though: How do you get $AB^\ast = B^\ast A$ and $A^\ast B = B A^\ast$ from $A,B$ normal and commuting?
Dec
7
awarded  Popular Question
Dec
7
comment Minkowski type inequality in Banach algebras
Did you mean for $A+B$ normal? I assume you want to apply the Gelfand representation. In any case, I was wondering if I may change Cauchy-Schwartz to Cauchy-Schwarz.
Dec
6
comment Cardinality of set difference
@Victor Ok, can you post the solution in an answer of your own then? By now you probably know the answer and I'd be interested to see it too.
Dec
6
revised homeomorphism between $2^{\mathbb{N}}$ and the Cantor Middle third set
Unsolicited tag nuked.
Dec
6
answered Reals constructed from equivalence classes of Cauchy sequences of rationals.
Nov
30
answered Cardinality of set difference
Nov
28
comment Cancellation of Direct Product in Grp
How do you read $\times$-compact? "product compact"? Did you invent this definition?
Nov
25
comment $\Bbb{R}^2$ not homeomorphic to $\Bbb{R}^2\setminus \{0\}$
Your question was answered here: math.stackexchange.com/a/30888/5798