# Jorge Fernández

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bio website location Mexico City age member for 2 years, 6 months seen 3 hours ago profile views 1,979

Hello, I am a freshman at The National Autonomous University of Mexico (UNAM).

My interests are contest problems,elementary number theory, combinatorics, graph theory, linear algebra, group theory, abstract algebra and I have been meaning to learn category theory and matroids.

# 2,909 Actions

 1d answered Set with distinct subset sums 1d comment How to solve this kind of problem? I solved it using integers, I think it becomes harder if we can only use naturals. 1d revised How to solve this kind of problem? added 267 characters in body 1d comment Check if Sequence is Graphic: 8, 8, 7, 7, 6, 6, 4, 3, 2, 1, 1, 1 I mean, you should count the degrees in the graph to make sure, but I can't find more conclusive evidence it is graphic 1d comment Check if Sequence is Graphic: 8, 8, 7, 7, 6, 6, 4, 3, 2, 1, 1, 1 Well, I counted the degrees in the graph in the solution and it is correct, are you sure you copied the sequence correctly? 1d answered How to solve this kind of problem? 1d comment How to solve this kind of problem? The number in the bottom right corner has to be $1,-1,11$ or $-11$ 1d answered Check if Sequence is Graphic: 8, 8, 7, 7, 6, 6, 4, 3, 2, 1, 1, 1 1d comment Is it possible to permute an unknown binary sequence so that two particular bits are equal? I editted it, is it convincing now? 1d revised Is it possible to permute an unknown binary sequence so that two particular bits are equal? added 886 characters in body 1d awarded abstract-algebra 2d comment An abelian subgroup of symmetric group Wow, that was pretty sweet. Using abelians are clt was rather ingenious. 2d comment Normal subgroups in groups of odd order I don't see why $H$ needs to be normal for the first proof. Couldn't we use the same argument without normality?That is: the order of $N_G(H)/C_G(H)$ divides the order of $N_G(H)$ and therefore the order of $G$. But it also divides the order of $Aut(H)$? since the order of $Aut(H)$ is relatively prime to the order of $G$ we get$C_G(N)=N_G(N)$. Oh, I see why you need it to be normal lol. 2d comment Normal subgroups in groups of odd order proposition $2$ can be proven using the thing about normal subgroups being a union of conjugacy classes.the smallest non trivial ones have size $p$. Although prop 2 is not generalization. 2d comment Normal subgroups in groups of odd order The proof of the proposition is the same isn't it? You get the order of $N_G(H)/C_G(H)$ divides the order of $\Aut(H)=p-1$ and the order of $N(G)$. Why does $H$ have to be normal though? Can't you get the same results without $H$ being normal? 2d comment Is it possible to permute an unknown binary sequence so that two particular bits are equal? My point is that he can safely assume the swap was done when $r>k$ and he can safely assume the swap was not done when $rk$ he knows that the sequence is going to be the same as the sequence when $b_r$ and $b_k$ are switched (because the only possibilities are $b_r=b_k=1$ or $b_r=1,b_k=0$. In both cases the string becomes the string when $b_r$ is switched with $b_k$ and everything stays the same. 2d accepted Is it possible to permute an unknown binary sequence so that two particular bits are equal? 2d comment Is it possible to permute an unknown binary sequence so that two particular bits are equal? well yes, but in this case the mathematician knows which where the "coordinates" of the diodes he did, what I mean is that he can reverse his own process.