Alternating chains and lattice strict singularity

Abstract

We present an alternating-chain argument intended to show that every lattice strictly singular operator from a real Banach lattice to a real Banach space is disjointly strictly singular. A hypothetical counterexample yields two LSS operators on a reflexive sequence lattice whose difference is bounded below. Quotienting by the range of that difference gives a common map bounded below on a positive tail cone. Finite chains of positive disjoint vectors, with alternating small differences, then lead to incompatible length estimates. We record the resulting operator and sequence consequences and extend the construction to common postcompositions with DSS errors. Independently of the proposed equality, we prove simultaneous nuclear restriction results for countable DSS families and uniform nuclear tails for norm-compact DSS families, together with common Hilbert-space factors and arbitrarily small nuclear corrections having a common infinite-dimensional kernel. Examples identify limits of these selection statements. The main equality is a candidate real-field proof; no complex-field equality is asserted.