Strong-Field Contact of Extreme Masses in Hyperbrane Relativity

Overview. This standalone preprint develops a conservative Hyperbrane Relativity (HBR) mechanism for binary neutron-star merger. The motivating question is direct: if the HBR push-restore reading of gravity gives ordinary non-contact stability through overlapping outer strain envelopes, why can compact neutron stars still merge? Central claim: neutron-star merger is not the failure of push-out stability; it is the strong-field continuation of push-out stability into a shared-strain branch. Mechanism. In weak-field systems, maintaining two separated push-out strain envelopes is the lower-cost variational branch. For extremely compact masses, the outer brane-response layer can approach a finite saturation capacity. Beyond a critical contact depth, preserving two independent saturated envelopes becomes more costly than forming one shared psi_bulk strain configuration. The merger is therefore described as a bifurcation from a separated two-body branch to a shared-strain branch in the energy landscape. No new pulling force is introduced. Main contributions. Strong-contact criterion: a coalescence condition written as the branch change between separated-envelope and shared-strain energy configurations. Native strain-functional route: a connection from the schematic branch ansatz to a local HBR strain functional, clarifying what future first-principle calculations must derive. Two-parameter phase map: a minimal contact phase map in the (eta, chi) plane, where eta is reduced contact depth and chi is an observer-side compactness proxy normalized by the saturation proxy. Ejecta interpretation: outer-layer saturation supplies a density-diffusion and surface-unbinding channel, while inner contact supplies the shared-strain coalescence that terminates the inspiral. Tidal continuity: ordinary tides are read as the subcritical weak-field continuation of the same strain-envelope overlap logic. Falsifiability structure: the paper records a tidal-deformability bound, a radiation-sector balance requirement, and a boundary-condition target for deriving the saturation scale S_sat. Relation to GW170817. For GW170817-like systems, the preprint separates three empirical anchors: inspiral before contact, merger/post-merger branch transition, and electromagnetic counterpart. It includes a qualitative observation-to-HBR correspondence table connecting inspiral, finite-size response, merger, kilonova ejecta, and heavy-element material to the corresponding HBR branch and outer-layer channels. Scope and limitations. This is a contact-sector mechanism paper. It is not a full waveform generator, not a first-principle neutron-star equation-of-state derivation, and not a numerical-relativity replacement. The paper explicitly lists the open calculations needed for a quantitative programme: a one-dimensional psi_bulk saturation solution, a concrete two-body variational model, a waveform tidal-map derivation, ejecta transport modeling, the HBR radiation-sector map, and post-contact remnant classification. Prepared upload state. Version v0.7; 16 pages. The PDF compiles with pdflatex, with no undefined references or citations and no Overfull or Underfull box warnings. HBR canonical verification reports PASS 28 / FAIL 0 / WARN 12; the V51 forbidden-language scan is clean.