P42 Gravitational Flash in CCEGA: A Post-Merger Spectral Signature from Density-Dependent Gravity in NS-NS Mergers

During the merger of two neutron stars, the remnant density transiently exceeds the CCEGA critical density ρc = 7.4 ρnuc. At this density, the effective gravitational coupling Geff(ρ) = GN exp(−ρ/ρc) drops to 0.368 GN, suppressing gravitational compression. We propose that this transient suppression produces a "gravitational flash": a brief period of reduced effective gravity during which the remnant undergoes a characteristic bounce. This bounce generates an additional spectral peak in the post-merger gravitational wave signal at fCCEGA ∼ 5 kHz — distinct from the dominant GR post-merger frequency f2 ∼ 2–3 kHz. Detection or non-detection of this peak by Einstein Telescope would constitute a direct test of the…