A generalization of Banach’s contraction principle

Ćirić, Lj. B.

doi:10.1090/S0002-9939-1974-0356011-2

A generalization of Banach’s contraction principle
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by Lj. B. Ćirić

Proc. Amer. Math. Soc. 45 (1974), 267-273

DOI: https://doi.org/10.1090/S0002-9939-1974-0356011-2

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Abstract:

Let $T:M \to M$ be a mapping of a metric space $(M,d)$ into itself. A mapping $T$ will be called a quasi-contraction iff $d(Tx,Ty) \leqslant q\max \{ d(x,y);d(x,Tx);d(y,Ty);d(x,Ty);d(y,Tx)\}$ for some $q < 1$ and all $x,y \in M$. In the present paper the mappings of this kind are investigated. The results presented here show that the condition of quasi-contractivity implies all conclusions of Banach’s contraction principle. Multi-valued quasi-contractions are also discussed.

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