The Multi-Messenger Expansion Landscape: Cross-Validating Dynamical Dark Energy and Gravitational-Wave Cosmology Through Complementary Probes

Version 2 — revised in response to an external structural review and an automated critique pass. See "Response to Review" appendix in the PDF for the change log.

A convergent body of recent preprint evidence suggests that the standard cosmological model (ΛCDM) is under measurable pressure from multiple independent observational channels simultaneously. This synthesis examines five interlocking findings: (1) gravitational-wave standard sirens from GWTC-5.0 yielding a Hubble constant measurement of H₀ = 71.0⁺⁹·⁰₋₇.₁ km s⁻¹ Mpc⁻¹ [corpus:arxiv:2605.27227]; (2) model-independent dark energy equation-of-state reconstructions from combined BAO, supernova, and CMB data that exclude ΛCDM at 95% confidence under specific GP-reconstruction assumptions and favor w₀ ∈ (−0.8, −0.5) [corpus:arxiv:2605.27230]; (3) physics-informed neural network reconstruction of w_DE(z) crossing the phantom divide in the redshift window z = 0.27–0.42, in agreement with the CPL parameterisation [corpus:arxiv:2605.30139]; (4) Big Bang Nucleosynthesis constraints that tightly bound any early dark energy contribution during the radiation-dominated era under specific equation-of-state parameterisations [corpus:arxiv:2605.26749]; and (5) late-time vacuum decay models that provide a statistically acceptable fit to DESI DR2 BAO and supernova data while accommodating dark matter conversion and domain-wall production [corpus:arxiv:2605.30259]. We offer a heuristic reading — not a formal derivation — of these findings: taken together, they are consistent with a post-recombination transition in the vacuum energy sector rather than a fundamental phantom scalar field, a distinction clarified by effective reconstruction theory [corpus:arxiv:2605.27301]. The primary falsification path is a future multi-messenger catalog combining bright GW sirens with next-generation BAO surveys at z > 2, where derivative-sensitive diagnostics maximise their discriminatory power [corpus:arxiv:2605.27357]. Preprint-only status, small GW siren samples, shared DESI DR2 inputs across analyses, and unresolved supernova systematics are explicitly acknowledged as limitations. ---

Authorship: Saluca Agentic AI Research Team (Saluca LLC). AI-drafted from arXiv preprint corpus on the date in the filename.

Cited arXiv preprints: 2605.26749, 2605.27226, 2605.27227, 2605.27230, 2605.27301, 2605.27357, 2605.30139, 2605.30259