Bornological stabilization families and oscillation dynamics of closed-set sequences

Abstract

Convergence of moving closed sets is usually studied relative to a family of test regions fixed in advance. This may conceal the regions on which a given sequence actually stabilizes. We introduce a sequence-dependent construction in a metric space. For each test set, we take the infimum over all tails of the supremum of the symmetric localized excess between pairs of tail members. The test sets for which this quantity is zero form the stabilization family. We prove that this family is hereditary and closed under finite unions, and hence is a bornology whenever it covers the ambient space. Under neighborhood stabilization and a compactness condition preventing local traces from escaping, we obtain either eventual disappearance from a test region or convergence to a nonempty local closed limit. A nested countable cofinal family then yields compatible local limits and a global cluster set. When this set is nonempty, bornological convergence follows. We further prove that every preassigned bornology supporting neighborhood convergence is contained in the generated neighborhood-stabilization family. Counterexamples separate the construction from global Hausdorff convergence and pointwise convergence of distance functions, and establish that compactness is indispensable. The novelty is that the testing bornology is derived from the tail behavior of the sequence itself. This construction may be useful for moving feasible sets and set-valued approximations that stabilize locally but not globally.