Pedro Lauridsen Ribeiro
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Jun
13
answered About timelike surfaces with non-diagonalizable shape operator.
Mar
7
comment Translation of a polynomial
Yep, you can sleep sound now ;-)
Mar
7
comment Translation of a polynomial
The second line is still wrong... :-P
Mar
7
comment Translation of a polynomial
In the second line of your last sequence of formulas, I believe that the exponent of $z_0$ is incorrect - it should be $k-j$ instead of $n-j$ since you are expanding $(z+z_0)^k$ with the inner sum (oops, Reveillark was faster than me, bummer)
Dec
28
awarded  Yearling
Dec
15
awarded  Caucus
Nov
16
answered Gathering books on Lorentzian Geometry
Feb
22
suggested rejected edit on Are $L_p$ spaces of functions with separable support separable?
Jun
6
comment Open neighborhoods of a $G_\delta$ set
@Cameron: nice indeed, but see my last comment on Asaf's answer...
Jun
6
comment Open neighborhoods of a $G_\delta$ set
It seems that disconnectedness of some of the sets involved plays a common role in all these counter-examples... My last move: what if $X$ is complete and connected, $A$ is connected and $A_n$ is connected for all $n\in\mathbb{N}$?
Jun
6
awarded  Commentator
Jun
6
comment Open neighborhoods of a $G_\delta$ set
Never mind, Asaf provided a suitable counter-example...
Jun
6
comment Open neighborhoods of a $G_\delta$ set
I've deleted a pair of messed-up comments before I could see your reply to one of them... You're right, $X$ here is totally disconnected.
Jun
6
awarded  Scholar
Jun
6
awarded  Supporter
Jun
6
accepted Open neighborhoods of a $G_\delta$ set
Jun
6
comment Open neighborhoods of a $G_\delta$ set
What if $X$ is assumed complete and connected as in your counter-example, but also that $A\neq\varnothing$?
Jun
6
comment Open neighborhoods of a $G_\delta$ set
Yeah, I got it... Can the possibility that $A$ is open and a proper subset of $A_n$ for each $n\in\mathbb{N}$ be evaded by assuming completeness and (say) connectedness of $X$? The latter property seems to fail in both counter-examples...
Jun
6
comment Open neighborhoods of a $G_\delta$ set
What if one assumes in addition that $X$ is complete (which is clearly false in your counter-example)?
Jun
6
awarded  Student