# Bruno Stonek

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bio website bruno.stonek.com location Montevideo, Uruguay age 25 member for 3 years, 9 months seen yesterday profile views 1,897

Math student in Université Paris 13.

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 Jan27 comment Does there exist a surface homemomorphic to a torus with positive Gaussian curvature? @Felipe: any compact surface in $\mathbb{R}^3$ has a point with positive curvature. Indeed, it is bounded, thus it lies inside of a big enough sphere. Now reduce the sphere's radio until it first touches the surface in a point. That point of the surface must therefore have positive curvature. (You should fill in the details for this argument). Jan27 comment Does there exist a surface homemomorphic to a torus with positive Gaussian curvature? @Felipe: no (deform a little bit the tip of a sphere for example), but the Euler characteristic is. Therein lies the power of Gauss-Bonnet! It combines topological data (Euler characteristic) with geometrical data (global curvature). Jan26 comment How to introduce category theory to a high school audience? I agree with what Martin said. The first examples that come to mind are lcm/gcd of integers and sup/inf of real numbers. There are many other elementary examples like these. Jan23 revised Verification of my solution of $xy'=2y$ changed undescriptive title Jan18 awarded Nice Question Jan18 reviewed Approve suggested edit on magical isoceles triangle and 13/15 ratio Jan18 reviewed Approve suggested edit on Show a module is simple Jan9 comment Stopping the “Will I need this for the test” question This is as depressing as it is true. Dec30 revised When are generalized Severi-Brauer varieties trivial? I mistook dimension for -reduced dimension-. Also, added link to the MO counterpart Dec28 reviewed Reject suggested edit on Solving $\phi(n)=22$ Dec27 reviewed Edit suggested edit on What is the benefit of the theory of categories? Dec27 revised What is the benefit of the theory of categories? edited some typos Dec27 revised When are generalized Severi-Brauer varieties trivial? edited tags Dec27 awarded Custodian Dec27 reviewed Approve suggested edit on Integral of $\frac{1}{x^4+1}$ Dec26 revised When are generalized Severi-Brauer varieties trivial? edited tags Dec26 comment A group of order 561 is cyclic. I don't understand how this question has 6 upvotes (as of now). Dec26 asked When are generalized Severi-Brauer varieties trivial? Dec10 awarded Popular Question Dec10 comment What to look for in a proof? Yes, I agree now. In fact I think both things are really useful: try to restate in your own words (and your own order!) and be verbose, i.e. understanding and justifying every single step, and also do what I said in the comment above: summarize the thing to the bare minimum, the core ideas.