Albert
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 Feb18 awarded Revival Oct21 awarded Teacher Oct21 answered Is there a common symbol for concatenating two (finite) sequences? Sep24 awarded Autobiographer May16 revised mean and variance normalization of vectors added 147 characters in body May14 revised mean and variance normalization of vectors edited tags May14 asked mean and variance normalization of vectors Dec14 comment How $x^4$ is strictly convex function? Note that the second derivative is positive almost everywhere. I'm pretty sure that this is also enough to get strict convexity. Jun8 accepted writing $M : \Gamma_{n,0} \backslash \Gamma_n$ May24 revised writing $M : \Gamma_{n,0} \backslash \Gamma_n$ better matrix May24 revised writing $M : \Gamma_{n,0} \backslash \Gamma_n$ added 84 characters in body May24 revised notation for invariation added 134 characters in body May24 comment How to write presentation of a group? Why do you write $e_i^2 = 1, e_i e_j = e_j e_i$? Couldn't you just write $e_i \in \mathbb{Z} / 2 \mathbb{Z}$? Or, if you want to have representations, $e_i \in \{0,1\}$? That somewhat seems simpler to me. May24 asked notation for invariation May24 asked writing $M : \Gamma_{n,0} \backslash \Gamma_n$ May13 awarded Scholar May13 accepted extended Euclidean (xgcd) in quadratic integer rings May13 revised extended Euclidean (xgcd) in quadratic integer rings added 361 characters in body May13 comment extended Euclidean (xgcd) in quadratic integer rings A bit more generic, where I need that: Given a matrix $M \in \operatorname{Sp}_2(\mathbb{K})$, I want to find $\gamma \in \operatorname{Sp}_2(\mathcal{O})$, $R \in \operatorname{Sp}_2(\mathbb{K})$ such that $M = \gamma \cdot R$ and I want the left lower $2 \times 2$ matrix of $R$ to be zero. In my construction, I heavily depend on the extended Euclidean algorithm. May13 comment extended Euclidean (xgcd) in quadratic integer rings In case it is an Euclidean domain, how would an implementation of the extended Euclidean algorithm look like? I mostly wonder about how to define/implement the division with remainder. -- Also, why would the non-Euclidean but UFD fail there? -- Is it easy to give an example where you cannot find $x,y$ in a non-UFD?