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Let ( X, d) be a compact metric space and let $$ \mathcal{M} $$( X) denote the space of all finite signed Borel measures on X. Define I: $$ \mathcal{M} $$( X) → ℝ by I(μ) = ∫ X∫ X d( x, y) dμ(x)dμ( y), and set M( X) = sup I(μ), where μ ranges over the collection of measures in $$ \mathcal{M} $$( X) of total mass 1. The space ( X, d) is quasihypermetric if I(μ) ≦ 0 for all measures μ in $$ \mathcal{M} $$( X) of total mass 0 and is strictly quasihypermetric if in addition the equality I(μ) = 0 holds amongst measures μ of mass 0 only for the zero measure. This paper explores the constant M( X) and other geometric aspects of X in the case when the space X is finite, focusing first on the significance of the maximal strictly quasihypermetric subspaces of a given finite quasihypermetric space and second on the class of finite metric spaces which are L1-embeddable. While most of the results are for finite spaces, several apply also in the general compact case. The analysis builds upon earlier more general work of the authors [11] [13]. [ABSTRACT FROM AUTHOR]

Let (X, d) be a compact metric space and let M(X) denote the space of all finite signed Borel measures on X. Define I : M)X) → ℝ by I (μ) = ∫X∫X d(x, y) dμ(x) dμ(y), and set M(X) = sup I (μ); where μ ranges over the collection of signed measures in M(X) of total mass 1. The metric space (X, d) is quasihypermetric if for all n ϵ ℕ, all α1,…, …n ϵ ℝ satisfying ∑i=1n αi and all x1,…,xn ϵ X, the inequality ∑i,j=1n αiαjd(xi, xj) ≤ 0 holds. Without the quasihypermetric property M(X) is infinite, while with the property a natural semi-inner product structure becomes available on M0(X), the subspace of M(X) of all measures of total mass 0. This paper explores: operators and functionals which provide natural links between the metric structure of (X, d), the semiinner product space structure of M0(X) and the Banach space C(X) of continuous real-valued functions on X; conditions equivalent to the quasihypermetric property; the topological properties of M0(X) with the topology induced by the semi-inner product, and especially the relation of this topology to the weak-* topology and the measure-norm topology on M0(X); and the functional-analytic properties of M0(X) as a semi-inner product space, including the question of its completeness. A later paper [P. Nickolas and R. Wolf, Distance geometry in quasihypermetric spaces. II, Math. Nachr., accepted] will apply the work of this paper to a detailed analysis of the constant M(X). [ABSTRACT FROM AUTHOR]