Bruno Le Floch
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 May17 comment Fermat Last Theorem for non Integer Exponents You can generalise this to show that the set of real n for which there exist integers $x, y, z$ with $x^n + y^n = z^n$ is dense in $[0,\infty)$. Nov17 awarded Student Oct22 comment How does $\sqrt{|e^{-y}\cos x + ie^{-y}\sin x|}= e^{-y}$ As it currently is, the question is wrong, so your answer is at best incomplete. $\sqrt{|e^{-y}\times ...|} = e^{-y/2}$, not $e^{-y}$. Aug1 comment Are there any synonyms of “pair of pants” in topology? I have also heard (and used) trinion, in some conformal field theory papers (we often manipulate Riemann surfaces in 2d CFT). Aug1 comment Are non-circular manholes possible? @J.M. You're right. However, the example of a spiral shows that Hans' question does have answers other than convex constant-diameter domains. Aug1 comment Are non-circular manholes possible? Hans-Peter, a spiral cover to a spiral hole would not pass through I think: doing what J.M. describes would get the spiral stuck after one turn, since the spiral would bang into the ground from below. Actually your way of stating the problem with an infinite plane is a bit odd, since that means that the ground is entirely hollow. A slightly different (but more realistic) situation is if the hole below ground level is $\mathbb{R}^+ \times \text{shape}$ where the shape is part of $\mathbb{R}^2$. Aug1 comment Are non-circular manholes possible? @J.M. I isn't clear: doing it in the naive way would get the cover will stuck when you try to pass the straight part through the hole. Jul30 comment Is there a simple explanation why degree 5 polynomials (and up) are unsolvable? @ErickWong My bad. You are right, let me retract my comment. Perhaps 'if it were possible to "invert" the polynomial $x^5−x$ (i.e. solve $x^5-x=c$ directly like we can $x^5=c$)' would be better? Jul29 comment Is there a simple explanation why degree 5 polynomials (and up) are unsolvable? Can't be $x^5-x$ since that has trivially $0$, $1$, $i$, $-1$ and $-i$ as solutions. Feb7 awarded Supporter Feb7 awarded Autobiographer