Revisiting Krasnoselskii’s fixed point theorem: Extensions and applications to operator equations
Abir Yakoub , Abdelaziz Mennouni , Ravi P. Agarwal
An International Journal of Optimization and Control: Theories & Applications ›› 2026, Vol. 16 ›› Issue (1) : 191 -204.
Fixed point theory stands as a fundamental pillar in nonlinear functional analysis, being essential for proving the existence of solutions for nonlinear differential and integral equations. Krasnoselskii’s hybrid fixed point theorem, which combines the Banach contraction principle with Schauder’s theorem, is a pivotal contribution. Recent efforts have focused on refining and relaxing the conditions of this theorem. This study aims to extend the theoretical framework of Krasnoselskii-type fixed point theorems to address a broader and more general class of nonlinear operator equations within a Banach algebra setting. It also seeks to establish rigorous conditions for the existence (and uniqueness, where possible) of solutions. The approach involves developing local variants of the classic Krasnoselskii fixed point theorems. We performed a comparative analysis of previous studies, introduced modifications to the operator equations to relax restrictive assumptions, and theoretically generalized the theorems to accommodate a complex structure involving four operators. To validate the results, they were applied to a nonlinear functional integral equation within the Banach space C[0,1]. We successfully generalized existing results by incorporating the Hölder continuity condition, which is less restrictive than the standard Lipschitz condition. The unified theoretical framework led to the establishment of a comprehensive set of theorems and corollaries covering a wide class of operator equations such as: $A x^{(\rho 2)} B x^{\rho 1}+C x^{(\rho 3)} D x^{\rho 1}=x$. Our results provide less restrictive local existence conditions and wider applicability in the analysis of complex mathematical systems.
Fixed point / Operator equations / Hölderian / Nonlinear functional / Lipschitzian / Integral equations
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| [6] |
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| [7] |
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| [8] |
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| [9] |
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| [10] |
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| [11] |
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| [12] |
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| [13] |
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| [14] |
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| [15] |
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| [16] |
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| [17] |
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| [18] |
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| [19] |
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| [20] |
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| [21] |
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| [22] |
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| [23] |
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| [24] |
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| [25] |
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| [26] |
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| [27] |
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| [28] |
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| [29] |
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| [30] |
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| [31] |
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| [32] |
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| [33] |
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