Emergent Cosmological Acceleration from Supermassive Black Hole Horizon Entropy

We propose that supermassive black holes contribute directly to the observed accelerated expansion of the universe through a horizon entropy-driven generation of effective spacetime volume. In this framework, the event horizon acts as a thermodynamic boundary where infalling mass increases the entropy-area term and leads to a net production of spacetime volume external to the black hole. This process yields an effective vacuum energy density that scales with the total population of supermassive black holes in the observable universe. The resulting value is consistent in order of magnitude with the observed cosmological constant Λ, providing a natural, astrophysical origin of dark energy without requiring exotic fields or modifications of general relativity.