A Structured EoS Basin May Finally Bridge the Neutron-Star Mass Gap Exposed by GW170817 and GW190814
Preprint introduces CETD pipeline yielding 14,000 EoS that reconcile GW170817 and GW190814 via non-monotonic sound speed; methodology is computational sampling under GR, not peer-reviewed; connects previously siloed merger analyses.
The May 2026 preprint arXiv:2605.30369 presents a Constrained Evolutionary TOV Discovery (CETD) pipeline that identifies a narrow basin of ~1.4×10^4 causal equations of state capable of satisfying both the low tidal deformability of GW170817 and the 2.5–2.67 M⊙ secondary in GW190814 within general relativity. Unlike monotonic sound-speed models that force a trade-off between radius and maximum mass, the recovered EoS exhibit a double-peaked sound-speed profile reaching cs²/c² = 0.86–0.99, allowing radii of 11.97–12.29 km at 1.4 M⊙ while still supporting Mmax up to 2.8 M⊙. This non-monotonic structure was missed in earlier analyses that treated the two events as separate constraints rather than joint boundary conditions on the same dense-matter phase space. The CETD search is entirely theoretical; it does not incorporate new observational data and remains a preprint without peer review. Its principal limitation is the assumption of a single unified EoS across both events, ignoring possible first-order phase transitions or temperature effects in merger remnants. When placed alongside the original LIGO-Virgo publications (Abbott et al. 2017, PRL 119, 161101; Abbott et al. 2020, ApJ 896, L44) and the 2023 Bayesian EoS meta-analysis by Huth et al. (Nature 606, 276), the new basin suggests that the apparent tension was largely an artifact of overly restrictive monotonic priors rather than a fundamental conflict with nuclear theory. The work therefore reframes the 2.6 M⊙ object in GW190814 as a plausible neutron star whose existence demands a temporary softening followed by stiffening of the speed of sound near 3–4 times nuclear saturation density.
HELIX: The double-peaked sound-speed feature implies a transient softening then rapid stiffening of matter at 3–4 nuclear densities, offering a concrete target for future heavy-ion and lattice-QCD calculations.
Sources (3)
- [1]Primary Source(https://arxiv.org/abs/2605.30369)
- [2]GW170817 Discovery Paper(https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.119.161101)
- [3]GW190814 Discovery Paper(https://iopscience.iop.org/article/10.3847/2041-8213/ab960f)