- (Un-)Countable union of open sets - Mathematics Stack Exchange
$\begingroup$ A remark: regardless of whether it is true that an infinite union or intersection of open sets is open, when you have a property that holds for every finite collection of sets (in this case, the union or intersection of any finite collection of open sets is open) the validity of the property for an infinite collection doesn't follow from that
- Show that - 1 2(4 - Un)$ - Mathematics Stack Exchange
We know (from a previous question) that Un is an increasing sequence and Un < $4$ Show that $4$ - Un+1 <(or =) 1 2(4-Un) I gave it a try and this is what I got :
- Mathematics Stack Exchange
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- Mnemonic for Integration by Parts formula? - Mathematics Stack Exchange
The Integration by Parts formula may be stated as: $$\\int uv' = uv - \\int u'v $$ I wonder if anyone has a clever mnemonic for the above formula What I often do is to derive it from the Product R
- modular arithmetic - Prove that that $U(n)$ is an abelian group . . .
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- $U(n) \\simeq \\frac{SU(n) \\times U(1)}{\\mathbb{Z}_{n}}$ isomorphism
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- functional analysis - Where can I find the paper Un théorème de . . .
J P Aubin, Un théorème de compacité, C R Acad Sc Paris, 256 (1963), pp 5042–5044 It seems this paper is the origin of the "famous" Aubin–Lions lemma This lemma is proved, for example, here and here, but I'd like to read the original work of Aubin However, all I got is only a brief review (from MathSciNet)
- Order of the group $U(n)$ - Mathematics Stack Exchange
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