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Jan
14
answered Why is $R-\lambda$ invertible for $|\lambda|<1$
Jan
13
awarded  Yearling
Jan
10
awarded  Popular Question
Jan
4
awarded  Notable Question
Jan
1
revised Parametrisation of the surface a torus
rolled back to a previous revision
Dec
28
comment Kreyszig's Functional Analysis Section 2.8: How is the canonical embedding map injective?
Certainly. Hahn Banach does not apply here, I deleted what I had written.
Dec
28
comment Kreyszig's Functional Analysis Section 2.8: How is the canonical embedding map injective?
And btw it's "Kreyszig" not "Kryszeg". Please also correct the spelling of his name in your other questions.
Dec
28
revised Kreyszig's Functional Analysis Section 2.8: How is the canonical embedding map injective?
edited title
Dec
28
awarded  Notable Question
Dec
27
comment What objects can belong in a group?
All characters appearing in this work are fictitious. Any resemblance to real persons, living or dead, is purely coincidental.
Dec
27
answered What objects can belong in a group?
Dec
27
comment Does $(X)(Y)=(XY)$ for $X,Y\subseteq R$?
@egreg Can you point me to a definition of "freely generated algebra"? I can only find "finitely generated algebra". Thanks in advance.
Dec
26
comment Does $(X)(Y)=(XY)$ for $X,Y\subseteq R$?
Perhaps you want to replace the tag examples-counterexamples by solution-verification?
Dec
26
answered Does $(X)(Y)=(XY)$ for $X,Y\subseteq R$?
Dec
25
revised What does the closure of a subset of a CW-complex look like? Like this?
edited title
Dec
22
answered Nonunital C*-Algebras: Morphism Contractive
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 $\text{SL}(n, \mathbb{R})$