on linear operators that preserve bj-orthogonality in 2-normed spaces

Let x be a real 2-banach space. we follow gunawan, mashadi, gemawati, nursupiamin and siwaningrum in saying that x is orthogonal to y if there exists a subspace v of x with codim(v ) = 1 such that ∥x+λy; z∥ ≥ ∥x; z∥ for every z ∈ v and λ ∈ r. in this paper we prove that every linear self mapping t: x → x which preserve orthogonality is a 2-isometry multiplied by a constant.