THE NORMING SET OF T ∈ L_s (Formula presented) FOR n = 3, 4, 5

Let n ∈ N, n ≥ 2 and (E, ‖ · ‖) a Banach space. An element (x₁, …, x_n) ∈ Eⁿ is called a norming point of T ∈ L(ⁿ E) if ‖x₁ ‖ = · · · = ‖x_n ‖ = 1 and |T (x₁, …, x_n)| = ‖T ‖, where L(ⁿ E) denotes the space of all continuous n-linear forms on E. For T ∈ L(ⁿ E), we define (Formula presented) Norm(T) is called the norming set of T. Let (Formula presented)= R2 with the ℓ₁-norm. In this paper, we characterize the norming set of T ∈ (Formula presented). Using this result, we completely describe the norming set of T ∈ L_s ((Formula presented)) for n = 3, 4, 5, where L_s (ⁿ (Formula presented) denotes the space of all symmetricn-linear forms onℓ21^..