5 papers
Refinements of the Blanco-Koldobsky-Turnšek Theorem
Jayanta Manna, Kalidas Mandal, Kallol Paul +1
We refine the well-known Blanco-Koldobsky-TurnÅ¡ek Theorem which states that a norm one linear operator defined on a Banach space is an isometry if and only if it preserves orthogo…
An improvement of the Blanco-Koldobsky-Turnšek characterization of isometries
Jayanta Manna, Kalidas Mandal, Kallol Paul +1
We present an improvement of the Blanco-Koldobsky-TurnÅ¡ek characterization of isometries in normed linear spaces by using the concept of level vectors of an operator. In this cont…
A study on preservation of parallel pairs and triangle equality attainment pairs
Jayanta Manna, Kalidas Mandal, Kallol Paul +1
This paper investigates the structure and preservation of parallel pairs and triangle equality attainment (TEA) pairs in normed linear spaces. We begin by providing functional char…
On approximate preservation of orthogonality and its application to isometries
Kalidas Mandal, Jayanta Manna, Kallol Paul +1
Motivated by the famous Blanco-Koldobsky-TurnÅ¡ek characterization of isometries, we study the \textit{approximate preservation of Birkhoff-James orthogonality by a linear operator…
On directional preservation of orthogonality and its application to isometries
Jayanta Manna, Kalidas Mandal, Kallol Paul +1
We study the local preservation of Birkhoff-James orthogonality by linear operators between normed linear spaces, at a point and in a particular direction. We obtain a complete cha…