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Math Forum » Discussions » sci.math.* » sci.math.independent

Topic: Lovelock and Rund: Star shaped set of points on a manifold
Replies: 7   Last Post: Jan 17, 2013 2:39 PM

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Butch Malahide

Posts: 885
Registered: 6/29/05
Re: Lovelock and Rund: Star shaped set of points on a manifold
Posted: Jan 16, 2013 4:07 PM
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On Jan 16, 2:34 pm, quasi <qu...@null.set> wrote:
> [. . .]
> U is star-shaped in the sense that any point in U is "visible"
> from (0,0).
>
> Thus, U need not be a disk.
>
> For example, any convex open set containing (0,0) qualifies.
>
> But U need not be convex either.
>
> For example, the interior of a Jewish star centered at (0,0)
> also qualifies.

O.K.

> Staying with the religious theme, the interior of a Christian
> cross centered at (0,0) qualifies as well.

I have my doubts about that. I guess it depends on how you define the
"center" of a Christian cross.

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