The Banach theorem states that if a (self) map on a complete metric space is Lipschitz with ratio $< 1$, it has a unique fixed point. What about modifying the hypotheses to say that the only condition the map satisfies is that $d(x, y) > d(f(x), f(y))$ where $x, y$ are in the domain? (I think this condition is known as "weakly contracting" I think that this type of map would fix a point if the metric space were compact, but what about in the general case where the metric space is not compact? Is there a counterexample?
2026-04-04 04:36:06.1775277366
Counterexample to a "modified" Banach Fixed Point Theorem?
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$X=[1,\infty)$ with the usual metrix, $f(x)=x+e^{-x}$. Use Mean Value Theorem to verify that the hypothesis is satisfied.