Renormalization group and UV completion of cosmological perturbations: Gravitational collapse as a critical phenomenon

Abstract

Cosmological perturbation theory is known to converge poorly for predicting the spherical collapse and void evolution of collisionless matter. Using the exact parametric solution as a testing ground, we develop two asymptotic methods in spherical symmetry that resolve the gravitational evolution to much higher accuracy than Lagrangian perturbation theory (LPT), which is the current gold standard in the literature. One of the methods selects a stable fixed-point solution of the renormalization-group flow equation, thereby predicting already at the leading order the critical exponent of the phase transition to collapsed structures. The other method completes the truncated LPT series far into the UV regime, by adding a non-analytic term that captures the critical nature of the gravitational collapse. We find that the UV method most accurately resolves the evolution of the nonlinear density as well as its one-point probability distribution function. Similarly accurate predictions are achieved with the renormalization-group method, especially when paired with Padé approximants. Further, our results yield new, very accurate, formulas to relate linear and nonlinear density contrasts. Finally, we chart possible ways on how to adapt our methods to the case of cosmological random field initial conditions.

11 pages + appendices and references, 10 figures, v3: updated Figs. 1,2,3,5 now showing sign changes in the particle positions after collapse; matches published version

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Cited by in corpus (6)

• BullFrog: Multi-step perturbation theory as a time integrator for cosmological simulations
• Starting Cosmological Simulations from the Big Bang
• Fast and accurate collapse-time predictions for collisionless matter
• Testing the assumptions of the Effective Field Theory of Large-Scale Structure
• On the origin of transient features in cosmological N-Body Simulations
• Post-collapse Lagrangian perturbation theory in three dimensions