2025MNRAS.540..716M

We present the first results from the Manticore Project, dubbed Manticore-Local, a suite of Bayesian constrained simulations of the nearby Universe, generated by fitting a physical structure formation model to the 2M++ galaxy catalogue using the BORG algorithm. This field-level inference yields physically consistent realizations of cosmic structure, leveraging a non-linear gravitational solver, a refined galaxy bias model, and physics-informed priors. The Manticore-Local posterior realizations evolve within a parent cosmological volume statistically consistent with Lambda-cold dark matter, demonstrated through extensive posterior predictive tests of power spectra, bispectra, initial condition Gaussianity, and the halo mass function. The inferred local supervolume ($R< 200$ Mpc, or $z \lesssim 0.05$) shows no significant deviation from cosmological expectations; notably, we find no evidence for a large local underdensity, with the mean density suppressed by only $\approx 5$per cent relative to the cosmic mean. Our model identifies high-significance counterparts for 14 prominent galaxy clusters - including Virgo, Coma, and Perseus - each within 1 deg of its observed sky position. Across the posterior ensemble, these counterparts are consistently detected with 2σ-4$\sigma$ significance, and their reconstructed masses and redshifts agree closely with observational estimates, confirming the inference's spatial and dynamical fidelity. The peculiar velocity field recovered by Manticore-Local achieves the highest Bayesian evidence across five independent data sets, surpassing state-of-the-art non-linear models, linear theory, Wiener filtering, and machine learning approaches. Unlike methods yielding only point estimates or using simplified dynamics, Manticore-Local provides a full Bayesian posterior over cosmic structure and evolution, enabling rigorous uncertainty quantification. These results establish Manticore-Local as the most advanced constrained realization suite of the local Universe to date, offering a robust statistical foundation for future studies of galaxy formation, velocity flows, and environmental dependencies in our cosmic neighbourhood.