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burtonpeterj
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Does there exist a compact subset $K$ of $\mathbb{R}^2$ and a point $p$ in $\mathbb{R}^2$ with the following property?

Let $x$ and $y$ be a pair of points in $K$ such that \begin{equation} |x-y| < \sup_{z,w \in K}|z-w| \end{equation} Then it is possible to rotate $K$ around its center to obtainthere exists a setrotation $K'$$R$ fixing $p$ such that $K'$$R(K)$ still contains both $x$ and $y$ and such that at least one if $x$ and $y$ lies in the interior of $K'$$R(K)$. You can take pretty much any definition you want for

Intuitively one would think that $p$ should in some sense be the 'center'‘center’ of $K$, but that’s not required for the application I have in mind.

Does there exist a compact subset $K$ of $\mathbb{R}^2$ with the following property?

Let $x$ and $y$ be a pair of points in $K$ such that \begin{equation} |x-y| < \sup_{z,w \in K}|z-w| \end{equation} Then it is possible to rotate $K$ around its center to obtain a set $K'$ such that $K'$ still contains both $x$ and $y$ and such that at least one if $x$ and $y$ lies in the interior of $K'$. You can take pretty much any definition you want for the 'center' of $K$.

Does there exist a compact subset $K$ of $\mathbb{R}^2$ and a point $p$ in $\mathbb{R}^2$ with the following property?

Let $x$ and $y$ be a pair of points in $K$ such that \begin{equation} |x-y| < \sup_{z,w \in K}|z-w| \end{equation} Then there exists a rotation $R$ fixing $p$ such that $R(K)$ still contains both $x$ and $y$ and such that at least one if $x$ and $y$ lies in the interior of $R(K)$.

Intuitively one would think that $p$ should in some sense be the ‘center’ of $K$, but that’s not required for the application I have in mind.

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burtonpeterj
  • 1.8k
  • 9
  • 16

Pairs not at maximal distance in compact set

Does there exist a compact subset $K$ of $\mathbb{R}^2$ with the following property?

Let $x$ and $y$ be a pair of points in $K$ such that \begin{equation} |x-y| < \sup_{z,w \in K}|z-w| \end{equation} Then it is possible to rotate $K$ around its center to obtain a set $K'$ such that $K'$ still contains both $x$ and $y$ and such that at least one if $x$ and $y$ lies in the interior of $K'$. You can take pretty much any definition you want for the 'center' of $K$.