arXiv subjects
Publications and source records attributed to Meaza Bogale.
We establish common fixed point theorems for two pairs of weakly compatible self-mappings using an auxiliary function of two variables. Unlike classical results, our theorems do not assume continuity of the mappings and require completeness of only one image set. The use of two-variable auxiliary functions allows us to unify and extend various existing fixed point theorems in metric spaces.
We establish common fixed point theorems for two pairs of weakly compatible self-mappings using an auxiliary function of two variables. Unlike classical results, our theorems do not assume continuity of the mappings and require completeness of only one image set. The use of two-variable auxiliary functions allows us to unify and extend various existing fixed point theorems in metric spaces.
This paper establishes new common fixed point theorems for weakly compatible mappings in metric spaces, relaxing traditional requirements such as continuity, compatibility, and reciprocal continuity. We present a unified framework for three self-mappings $T$, $f$, and $g$ with a contractive condition involving a control function $ψ$, along with corollaries extending results to pairs of mappings and upper semi-continuous control functions. Further generalizations include iterated mappings and sequences of mappings. Rigorous examples demonstrate the necessity of hypotheses and show our results strictly generalize theorems by Al-Thagafi \emph{et. al.} \cite{Al-Thagafi2006}, Babu \emph{et. al.} \cite{Babu2007}, Jungck \cite{Jungck1976,Jungck1986}, Singh \cite{Singh1986,Singh1997a}, Som \cite{Som2003}, Song \cite{Song2007} and Zhang \emph{et. al.} \cite{Zhang2008}. Key advancements include eliminating completeness assumptions on the entire space and relaxing mapping compatibility conditions.
We establish the existence of common fixed points for $C_q$-commuting self-mappings satisfying a generalized Gregus-type inequality with quadratic terms in $q$-starshaped subsets of normed linear spaces. Our framework extends classical fixed point theory through: (i) Set-distance constraints $δ(\cdot, [q, \cdot])$ generalizing norm conditions (ii) Compatibility via $C_q$-commutativity without full affinity requirements (iii) Reciprocal continuity replacing full map continuity. Explicit examples (e.g., Example 2.6) demonstrate the non-triviality of these extensions. As applications, we derive invariant approximation theorems for best approximation sets. Our results generalize Nashine's work \cite{Nashine2007} and unify several known fixed point theorems.
Let $B_n$ (resp. $U_n$, $N_n$) be the set of $n\times n$ nonsingular (resp. unit, nilpotent) upper triangular matrices. We use a novel approach to explore the $B_n$-similarity orbits in $N_n$. The Belitski\uı's canonical form of $A\in N_n$ under $B_n$-similarity is in $QU_n$ where $Q$ is the subpermutation such that $A\in B_n QB_n$. Using graph representations and $U_n$-similarity actions stablizing $QU_n$, we obtain new properties of the Belitski\uı's canonical forms and present an efficient algorithm to find the Belitski\uı's canonical forms in $N_n$. As consequences, we construct new Belitski\uı's canonical forms in all $N_n$'s, list all Belitski\uı's canonical forms for $n=7, 8$, and show examples of 3-nilpotent Belitski\uı's canonical forms in $N_n$ with arbitrary numbers of parameters up to $\operatorname{O}(n^2)$.