Geometric Dual Origin of the Inaccessibility of Light Speed Upper Bound and Absolute Zero — Topological Boundary Principle in the Framework of Mem-force Theory

The inaccessibility of light speed upper bound and absolute zero are two fundamental constraints in modern physics: the former originates from special relativity and causality, while the latter from the third law of thermodynamics. These two limits lack a unified theoretical origin so far. Within the framework of Mem-force Theory (MFT), this paper proposes the vacuum geometric dual boundary conjecture: these two unbreakable physical limits are a pair of dual topological boundaries imposed by the D_8 geometric structure of the vacuum. The speed of light corresponds to the dynamic upper bound of vacuum perturbation propagation, determined by the density-dependent restoring force and impedance mechanism of the vacuum. Absolute zero corresponds to the thermodynamic lower bound of the vacuum ground state, forbidden by the minimal geometric fluctuation protected by D_8 symmetry. This paper clearly gives the geometric definition of time: time is the causal order parameter of vacuum geometric perturbations rather than a preset background. On this basis, we construct dimensionally consistent field equations, rigorous dispersion relations, non-circular derivation logic, form a unified interpretation fully compatible with existing theories, and propose two falsifiable quantitative predictions. This paper does not constitute a complete mathematical proof, but provides a self-consistent, rigorous, and testable unified hypothesis.