5 papers · 1 filter
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-Turnšek characterization of isometries in normed linear spaces by using the concept of level vectors of an operator. In this conte…
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…
Refinements of the Blanco-Koldobsky-Turnšek Theorem
Jayanta Manna, Kalidas Mandal, Kallol Paul +1
We refine the well-known Blanco-Koldobsky-Turnšek Theorem which states that a norm one linear operator defined on a Banach space is an isometry if and only if it preserves orthogon…
On approximate preservation of orthogonality and its application to isometries
Kalidas Mandal, Jayanta Manna, Kallol Paul +1
Motivated by the famous Blanco-Koldobsky-Turnšek 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…