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Article Citation - WoS: 10Citation - Scopus: 9Some Inevitable Remarks on "tripled Fixed Point Theorems for Mixed Monotone Kannan Type Contractive Mappings"(Hindawi Publishing Corp, 2014) Alsulami, Hamed H.; Roldan-Lopez-de-Hierro, Antonio-Francisco; Karapinar, Erdal; Radenovic, StojanWe advise that the proof of Theorem 12 given by Borcut et al. (2014) is not correct, and it cannot be corrected using the same technique. Furthermore, we present some similar results as an approximation to the opened question if that statement is valid.Article Citation - WoS: 3Citation - Scopus: 3An Illusion: "a Suzuki Type Coupled Fixed Point Theorem"(Hindawi Publishing Corporation, 2014) Alsulami, Hamed H.; Karapinar, Erdal; Kutbi, Marwan A.; Roldan-Lopez-de-Hierro, Antonio-FranciscoWe admonish to be careful on studying coupled fixed point theorems since most of the reported fixed point results can be easily derived from the existing corresponding theorems in the literature. In particular, we notice that the recent paper [Semwal and Dimri (2014)] has gaps and the announced result is false. The authors claimed that their result generalized the main result in [Doric and Lazovic (2011)] but, in fact, the contrary case is true. Finally, we present a fixed point theorem for Suzuki type (alpha, r)-admissible contractions.Article Citation - Scopus: 1Some Remarks About the Existence of Coupled g-coincidence Points(Springeropen, 2015) Erhan, Inci M.; Roldan-Lopez-de-Hierro, Antonio-Francisco; Shahzad, NaseerVery recently, in a series of subsequent papers, Nan and Charoensawan introduced the notion of g-coincidence point of two mappings in different settings (metric spaces and G-metric spaces) and proved some theorems in order to guarantee the existence and uniqueness of such kind of points. Although their notion seems to be attractive, in this paper, we show how this concept can be reduced to the unidimensional notion of coincidence point, and how their main theorems can be seen as particular cases of existing results. Moreover, we prove that the proofs of their main statements have some gaps.Article Citation - WoS: 40Citation - Scopus: 52Discussion on Generalized-(αψ, Βφ)-Contractive Mappings Via Generalized Altering Distance Function and Related Fixed Point Theorems(Hindawi Ltd, 2014) Berzig, Maher; Karapinar, Erdal; Roldan-Lopez-de-Hierro, Antonio-FranciscoWe extend the notion of (alpha psi, beta phi)-contractive mapping, a very recent concept by Berzig and Karapinar. This allows us to consider contractive conditions that generalize a wide range of nonexpansive mappings in the setting of metric spaces provided with binary relations that are not necessarily neither partial orders nor preorders. Thus, using this kind of contractive mappings, we show some related fixed point theorems that improve some well known recent results and can be applied in a variety of contexts.Article Citation - WoS: 28Citation - Scopus: 33Coincidence Point Theorems in Quasi-Metric Spaces Without Assuming the Mixed Monotone Property and Consequences in g-metric Spaces(Springer international Publishing Ag, 2014) Roldan-Lopez-de-Hierro, Antonio-Francisco; Karapinar, Erdal; de la Sen, ManuelIn this paper, we present some coincidence point theorems in the setting of quasi-metric spaces that can be applied to operators which not necessarily have the mixed monotone property. As a consequence, we particularize our results to the field of metric spaces, partially ordered metric spaces and G-metric spaces, obtaining some very recent results. Finally, we show how to use our main theorems to obtain coupled, tripled, quadrupled and multidimensional coincidence point results.Article Citation - WoS: 57Citation - Scopus: 65A Proposal to the Study of Contractions in Quasi-Metric Spaces(Hindawi Ltd, 2014) Alsulami, Hamed H.; Karapinar, Erdal; Khojasteh, Farshid; Roldan-Lopez-de-Hierro, Antonio-FranciscoWe investigate the existence and uniqueness of a fixed point of an operator via simultaneous functions in the setting of complete quasi-metric spaces. Our results generalize and improve several recent results in literature.Article Citation - WoS: 12Citation - Scopus: 21On Some Fixed Point Theorems Under (α, Ψ, Φ)-Contractivity Conditions in Metric Spaces Endowed With Transitive Binary Relations(Springer international Publishing Ag, 2015) Shahzad, Naseer; Karapinar, Erdal; Roldan-Lopez-de-Hierro, Antonio-FranciscoAfter the appearance of Nieto and Rodriguez-Lopez's theorem, the branch of fixed point theory devoted to the setting of partially ordered metric spaces have attracted much attention in the last years, especially when coupled, tripled, quadrupled and, in general, multidimensional fixed points are studied. Almost all papers in this direction have been forced to present two results assuming two different hypotheses: the involved mapping should be continuous or the metric framework should be regular. Both conditions seem to be different in nature because one of them refers to the mapping and the other one is assumed on the ambient space. In this paper, we unify such different conditions in a unique one. By introducing the notion of continuity of a mapping from a metric space into itself depending on a function alpha, which is the case that covers the partially ordered setting, we extend some very recent theorems involving control functions that only must be lower/upper semi-continuous from the right. Finally, we use metric spaces endowed with transitive binary relations rather than partial orders.
