FLUMEN: Neural Emulator of an Advanced Stochastic Weak Lensing Model — E8 Intelligence Research

Weak gravitational lensing by intervening structure magnifies distant sources and induces scatter in their luminosity distances. We develop an improved stochastic model for the distribution of weak lensing magnifications, $\textrm{d} P/\textrm{d}μ$, that resolves individual lenses down to $10^7\,M_\odot$ and, besides field halos and filaments, includes subhalos and large-scale clustering of the lens population. Both extensions broaden the distribution, and the resulting scatter in the luminosity distances agrees with the halo-model prediction from the nonlinear matter power spectrum and exceeds that obtained from $N$-body ray tracing, which we attribute to the finite mass resolution and box size of the simulations. Building on this model, we develop \texttt{FLUMEN}, a conditional normalizing-flow emulator that predicts $\textrm{d} P/\textrm{d}μ$ as a function of the source redshift up to $z_s=12$ and six cosmological parameters $\{h,Ω_M,Ω_B,σ_8,n_s,z_{\rm eq}\}$. The emulator enforces Author: Andrew Stewart Caldin, Independent Researcher, UK. Part of the E8 Intelligence Research series. Platform: e8intelligence.com