4,111 reputation
21647
bio website bruno.stonek.com
location Montevideo, Uruguay
age 25
visits member for 3 years, 9 months
seen yesterday

Math student in Université Paris 13.


Jan
27
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).
Jan
27
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).
Jan
26
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.
Jan
23
revised Verification of my solution of $xy'=2y$
changed undescriptive title
Jan
18
awarded  Nice Question
Jan
18
reviewed Approve suggested edit on magical isoceles triangle and 13/15 ratio
Jan
18
reviewed Approve suggested edit on Show a module is simple
Jan
9
comment Stopping the “Will I need this for the test” question
This is as depressing as it is true.
Dec
30
revised When are generalized Severi-Brauer varieties trivial?
I mistook dimension for -reduced dimension-. Also, added link to the MO counterpart
Dec
28
reviewed Reject suggested edit on Solving $\phi(n)=22$
Dec
27
reviewed Edit suggested edit on What is the benefit of the theory of categories?
Dec
27
revised What is the benefit of the theory of categories?
edited some typos
Dec
27
revised When are generalized Severi-Brauer varieties trivial?
edited tags
Dec
27
awarded  Custodian
Dec
27
reviewed Approve suggested edit on Integral of $\frac{1}{x^4+1}$
Dec
26
revised When are generalized Severi-Brauer varieties trivial?
edited tags
Dec
26
comment A group of order 561 is cyclic.
I don't understand how this question has 6 upvotes (as of now).
Dec
26
asked When are generalized Severi-Brauer varieties trivial?
Dec
10
awarded  Popular Question
Dec
10
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.