The Outside of the Universe as a Negative-Energy World: A Boundary Cosmology Proposal

This paper proposes a speculative but structured cosmological model built on three linked assumptions: the total energy of reality is zero, the observed universe may be modeled as a closed positive-energy world, and a corresponding negative-energy exterior exists beyond ordinary spacetime. The balancing negative sector is assigned to an exterior domain called the negative world, while the observable universe is treated as the positive world. The ultimate edge of cosmic expansion is interpreted not merely as an observational limit but as a terminal ontological interface at which the positive and negative worlds meet and cancel. The paper adopts the FLRW framework as a minimal geometric background, introduces the first Friedmann equation, and states a global balance condition E_tot = E+ + E- = 0 as a working hypothesis. This work is presented as a conceptual research program in boundary cosmology rather than a completed physical theory.