# Bruno Stonek

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bio website bruno.stonek.com location Montevideo, Uruguay age 25 member for 3 years, 10 months seen 5 hours ago profile views 1,936

Math student in Université Paris 13.

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 Dec10 comment What to look for in a proof? One thing which in my very humble opinion is nice to do, is to try to reduce the proof to a couple of sentences. That way you do your best to capture the essence of the proof, which is the most important thing to do. Dec10 accepted Every 4-dimensional isotropic quadratic space of determinant 1 is hyperbolic Dec10 accepted In a complete perfect metric space, transitive distance-preserving maps are minimal Dec1 awarded Popular Question Nov28 comment tensor product and direct product of algebra presentations I think you meant $xy-yx$ on your displayed equation. Nov26 asked Is an integer a sum of two rational squares iff it is a sum of two integer squares? Nov26 comment Every 4-dimensional isotropic quadratic space of determinant 1 is hyperbolic The thing is, the same proof that any 2-dimensional isotropic quadratic space is hyperbolic proves that any isotropic quadratic space contains an hyperbolic plane! That's the essential piece I was missing out on. Nov26 answered Every 4-dimensional isotropic quadratic space of determinant 1 is hyperbolic Nov21 accepted How to prove that two dilations of $\mathbb R^n$ are conjugate? Nov21 asked Every 4-dimensional isotropic quadratic space of determinant 1 is hyperbolic Nov14 comment In a complete perfect metric space, transitive distance-preserving maps are minimal Gracias Gordo por la ayuda. Nov14 answered In a complete perfect metric space, transitive distance-preserving maps are minimal Nov13 asked In a complete perfect metric space, transitive distance-preserving maps are minimal Nov12 comment How to prove that two dilations of $\mathbb R^n$ are conjugate? Thank you, it's all clear now. It's a nice idea to choose "fundamental domains" (hadn't thought of that in this context), define the homeos there, then extend as you do. I'll keep it in mind. Nov12 comment How to prove that two dilations of $\mathbb R^n$ are conjugate? Thanks! That's really what I was trying to do. Your signs are a bit odd (remember I imposed $\lambda_i>1$, what you wrote works for $\lambda_i<1$). How did you figure out how to define $h^*$? Nov12 comment How to prove that two dilations of $\mathbb R^n$ are conjugate? Thank you for your answer. Could you elaborate a little bit, maybe expand on what you mean by "take logs to reduce the problem to..."? Nov12 accepted Does Proj induce some equivalence of categories involving graded rings? Nov12 accepted If $f^n$ is mixing then $f$ is mixing? Nov12 accepted Hartshorne, exercise II.2.18: a ring morphism is surjective if it induces a homeomorphism into a closed subset, and the sheaf map is surjective Nov12 accepted Does inclusion of an affine open into an affine scheme correspond to restriction?