Separating the Universe into the Real and Fake

Abstract

The separate universe technique provides a means of establishing consistency relations between short wavelength observables and the long wavelength matter density fluctuations within which they evolve by absorbing the latter into the cosmological background. We extend it to cases where non-gravitational forces introduce a Jeans scale in other species like dynamical dark energy or massive neutrinos. The technique matches the synchronous gauge matter density fluctuations to the local expansion using the acceleration equation and accounts for the temporal nonlocality and scale dependence of the long wavelength response of small scale matter observables, e.g. the nonlinear power spectrum, halo abundance and the implied halo bias, and $N$-point correlation functions. Above the Jeans scale, the local Friedmann equation relates the expansion to real energy densities and a curvature that is constant in comoving coordinates. Below the Jeans scale, the curvature evolves and acts like a fake density component. In all cases, the matter evolution on small scales is correctly modeled as we illustrate using scalar field dark energy with adiabatic or isocurvature initial conditions across the Jeans scale set by its finite sound speed.

14 pages, 4 figures

References in corpus (6)

• Separate Universe Simulations
• Position-dependent power spectrum of the large-scale structure: a novel method to measure the squeezed-limit bispectrum
• Halo bias in mixed dark matter cosmologies
• Super-Sample Signal
• The Evolution of Bias - Generalized
• Scale-dependent halo bias from scale-dependent growth

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• Efficient Computation of Galaxy Bias with Neutrinos and Other Relics
• Super-sample covariance approximations and partial sky coverage
• Cosmological N-Body Simulations with a Large-Scale Tidal Field
• The impact of large-scale tides on cosmological distortions via redshift-space power spectrum
• Response approach to the squeezed-limit bispectrum: application to the correlation of quasar and Lyman-$\alpha$ forest power spectrum
• Gravitational wave fossils in nonlinear regime: halo tidal bias and intrinsic alignments from gravitational wave separate universe simulations
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• Spectral Distortion Anisotropy from Inflation for Primordial Black Holes
• Measurement of Void Bias Using Separate Universe Simulations
• Separate Universe Void Bias
• Relativistic bias in neutrino cosmologies
• Separate Universes beyond General Relativity
• Estimating the Integrated Bispectrum from Weak Lensing Maps
• Quintessential Isocurvature in Separate Universe Simulations
• Accurate method for ultralight axion CMB and matter power spectra
• Position-dependent Voronoi probability distribution functions for matter and halos
• Scale-dependent halo bias and the squeezed limit bispectrum in the presence of radiation
• Curvature Perturbations in the Effective Field Theory of Inflation
• Dark Matter Isocurvature from Curvature