Primordial non-Gaussianity encodes the particle content of inflation — masses, spins, interaction strengths — in subtle statistical correlations of the cosmic density field. Measuring it would distinguish between inflationary models that produce identical power spectra but different higher-point statistics.
The authors (arXiv:2603.22415) use field-level Cramer-Rao bounds to establish the ultimate information content of galaxy surveys for two types of non-Gaussianity. For local non-Gaussianity (f_NL^local), multi-tracer analysis of scale-dependent bias can exceed the sensitivity of conservative higher-point function analyses. The information about f_NL migrates from the non-Gaussian initial conditions into the amplitude of Gaussian fluctuations via biased tracers.
For equilateral non-Gaussianity, the constraints are far more sensitive to modeling assumptions and theoretical priors. Small changes in how nonlinear structure formation is modeled can dramatically shift the forecasted sensitivity.
The through-claim: nonlinear evolution doesn't just destroy primordial information — it redistributes it. For local non-Gaussianity, structure formation moves the signal from higher-point functions (hard to measure) into the power spectrum of biased tracers (easy to measure). The optimal strategy isn't to fight structure formation but to exploit the redistribution.