Closure and Relational Openness in Fundamental Physics: A Conceptual Framework for Weakly Coupled Cosmological Scalars

Contemporary cosmology accommodates light scalar fields, environmental screening mechanisms, and tightly constrained variations of fundamental constants. While these ingredients are technically consistent and phenomenologically viable, their coexistence often lacks a unified conceptual interpretation. This document presents a conceptual framework for understanding weakly coupled cosmological scalars in terms of a structural duality between closure—associated with symmetry, conservation, and stability—and relational openness—associated with contextual coupling, environmental dependence, and slow cosmological evolution. These notions are introduced as interpretative labels rather than new physical entities, and do not modify the underlying equations of motion. The framework clarifies why scalar-mediated effects are generically small, cumulative, and environment-dependent, and why null observational results are as informative as positive detections. It is intended as a conceptual companion to technical scalar–tensor models and phenomenological studies submitted separately to peer-reviewed journals.