Environmental Coupling Between Cosmic Expansion and Structure Growth in Voids

We present a concise empirical analysis testing whether local variations of the cosmic expansion rate are correlated with a suppression of structure growth in underdense (void) environments. The study is deliberately model-independent and does not assume any specific modification of gravity or dark-energy parametrization. Using standard observational ingredients and void-based environmental statistics, we test for a coupling between local expansion dynamics and growth observables. The work is motivated by recent interest in environment-dependent cosmological effects and provides a falsifiable observational test that is absent in the standard homogeneous ΛCDM framework. The analysis is designed to be directly applicable to current and upcoming survey data. This preprint is uploaded to establish priority and to support arXiv submission. It represents the version intended for public dissemination.