Vacuum is one of the most fundamental and conceptually contested concepts in modern physics. Standard quantum field theory describes it as the vacuum state of quantum fields, explaining phenomena such as zero-point energy, the Casimir effect, tunneling, and Hawking radiation in terms of zero-point energy, mode restriction, and fluctuations. Yet these descriptions leave ontological questions open: what is vacuum as such, whether so-called virtual particles require independent ontological status, and whether a more unified explanatory language exists for vacuum-related phenomena. This paper proposes a convergent interpretation within the framework of Energy-Efficiency Theory (EET): vacuum can be understood as the ground-state continuous distribution of free-state energy—the free-state background not yet locked into macroscopic constrained states. On this basis, “virtual particles” are not treated as independent microscopic entities but interpreted as transient local fluctuations or incomplete constraint events within the free-state background; the Casimir effect, quantum tunneling, and Hawking radiation are unified as “modulation of the free-state background by constraint boundaries.” The paper explicitly distinguishes two types of results: those that recover and reinterpret existing relations within EET, and those that can be advanced as candidate phenomenological hypotheses. The goal is not to replace quantum field theory in a single paper, but to provide a more unified, hierarchically clearer energy-ontological language for vacuum phenomena.
Yang (2026) studied this question.