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Post Closed as "Not suitable for this site" by David Roberts, Emil Jeřábek, Wolfgang, Nik Weaver, Yemon Choi
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Andrés E. Caicedo
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doesDoes there exist anya bounded set A in $\mathbb{R}_n$$A \subset \mathbb{R}^ n$ (for some n$n$) and anya function f from A to A $f:A\to A$ (not necessarily onto) such that $\forall x,y \in A$ distance(x,y) < distance(f(x),f(y))then $\|x-y\| < \|f(x)-f(y)\|$? And if

If such a set A $A$ (and a function f$f$) exists, does there even exist such a set A$A$ and a function f$f$ such that f$f$ is continuous? (Or - can it be proved that such a continuous f$f$ doesn't exist?)

does there exist any bounded set A in $\mathbb{R}_n$ (for some n) and any function f from A to A (not necessarily onto) such that $\forall x,y \in A$ distance(x,y) < distance(f(x),f(y))? And if such set A (and function f) exists, does there even exist such set A and function f such that f is continuous? (Or - can it be proved that such continuous f doesn't exist?)

Does there exist a bounded set $A \subset \mathbb{R}^ n$ (for some $n$) and a function $f:A\to A$ (not necessarily onto) such that $\forall x,y \in A$ then $\|x-y\| < \|f(x)-f(y)\|$?

If such a set $A$ (and a function $f$) exists, does there even exist such a set $A$ and a function $f$ such that $f$ is continuous? (Or - can it be proved that such a continuous $f$ doesn't exist?)

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Function and distance on bounded set

does there exist any bounded set A in $\mathbb{R}_n$ (for some n) and any function f from A to A (not necessarily onto) such that $\forall x,y \in A$ distance(x,y) < distance(f(x),f(y))? And if such set A (and function f) exists, does there even exist such set A and function f such that f is continuous? (Or - can it be proved that such continuous f doesn't exist?)