Fusion is not only an energy-over-barrier problem. It is a boundary-bridge-closure event: nuclei encounter the U(1) Coulomb boundary, a bridge-catalyst modifies crossing admissibility, and successful crossing resolves into stable nuclear closure capture. The catalyst is not the fuel; it is the bridge architecture. Fusion power is usually framed as a problem of overcoming the Coulomb barrier through temperature, pressure, confinement, compression, or tunneling probability. This paper proposes a complementary reconstruction: the Coulomb barrier should also be treated as a boundary-interface whose crossing depends on bridge conditions. In this view, fusion is not merely an energy-over-barrier event. It is a boundary-bridge-closure event. The central proposal is Coulomb Boundary-Bridge Fusion: a research program in which the Coulomb barrier is interpreted as the U(1) electrostatic boundary between nuclear coherence domains, while fusion-enabling conditions are interpreted as bridge operators that increase the admissibility of crossing and the probability of stable nuclear closure capture. This paper introduces the Coulomb Catalyst Hypothesis: a third atomic, isotopic, lattice, plasma, or field-structured domain may function as a Coulomb bridge-catalyst by reducing effective Coulomb discontinuity, improving pathway compatibility, creating resonant crossing windows, or increasing closure-capture probability. The paper does not claim that the Coulomb barrier is incorrect, that standard fusion physics is invalid, or that a working fusion catalyst has already been identified. It proposes a new conceptual and experimental search category: bridge-material discovery. A Coulomb bridge-catalyst is not the fusion fuel itself; it is the boundary-condition environment that makes fusion more admissible. The result is a framework for ranking candidate materials and environments through a Coulomb Bridge-Catalyst Index, based on screening capacity, polarizability, lattice geometry, phonon/plasmon resonance, spin compatibility, nuclear closure compatibility, and loss suppression. Keywords Coulomb barrier; fusion; Coulomb catalyst; bridge-catalysis; coherence discontinuity; nuclear closure; atomic resonance; electron screening; lattice confinement; phonon resonance; plasmon resonance; selective permeability; U(1); SU(2); SU(3); infratier closure; bridge operator.
Philip Lilien (Mon,) studied this question.