(i) ∥x1, x2, . . . , xn∥ = 0 if any only if x1, x2, . . . , xn are linearly dependent, (ii) ∥x1, x2, . . . , xn∥ is invariant under any permutation, (iii) ∥x1, x2, . . . , axn∥ = |a| ∥x1, x2, . . . , xn∥, for any a ∈ R (real), (iv) ∥x1, x2, . . . , xn−1, y + z∥ = ∥x1, x2, . . . , xn−1, y∥ + ∥x1, x2, . . . , xn−1, z∥ is called an n-norm on X and the pair (X, ∥•, . . . , •∥) is called n-normed li...

In this paper we describe the proof of ’Riesz Theorems’ in 2inner product spaces. The main result holds only for a b-linear functional but not for a bilinear functional. AMS Mathematics Subject Classification (2010): 41A65, 41A15

This is also called the dot product and written X ·Y . The inner product of two vectors is a number, not another vector. In particular, we have the vital identity ‖X‖2 = 〈X , X〉 relating the inner product and norm. For added clarity, it is sometimes useful to write the inner product in Rn as 〈X , Y 〉Rn . Example: In R4 , if X = (1,2,−2,0) and Y = (−1,2,3,4) , then 〈X , Y 〉 = (1)(−1) + (2)(2)+(−...

The notion of the shell of a Hilbert space operator, which is a useful generalization (proposed by Wielandt) of the numerical range, is extended to operators in spaces with an indefinite inner product. For the most part, finite dimensional spaces are considered. Geometric properties of shells (convexity, boundedness, being a subset of a line, etc.) are described, as well as shells of operators ...