Kinetic Field Theory: Effects of momentum correlations on the cosmic density-fluctuation power spectrum

Abstract

In earlier work, we have developed a Kinetic Field Theory (KFT) for cosmological structure formation and showed that the non-linear density-fluctuation power spectrum known from numerical simulations can be reproduced quite well even if particle interactions are taken into account to first order only. Besides approximating gravitational interactions, we had to truncate the initial correlation hierarchy of particle momenta at the second order. Here, we substantially simplify KFT. We show that its central object, the free generating functional, can be factorized, taking the full hierarchy of momentum correlations into account. The factors appearing in the generating functional, which we identify as non-linearly evolved density-fluctuation power spectra, have a universal form and can thus be tabulated for fast access in perturbation schemes. In this paper, we focus on a complete evaluation of the free generating functional of KFT, not including particle interactions yet. This implies that the non-linearly evolved power spectra contain a damping term which reflects that structures are being wiped out at late times by free streaming. Once particle interactions will be taken into account, they will compensate this damping. If we suppress this damping in a way suggested by the fluctuation-dissipation relations of KFT, our results show that the complete hierarchy of initial momentum correlations is responsible for a large part of the characteristic non-linear deformation and the mode transport in the density-fluctuation power spectrum. Without any adjustable parameters, KFT accurately reproduces the scale at which non-linear evolution sets in. Finally, we further develop perturbation theory based on the factorization of the generating functional and propose a diagrammatic scheme for the perturbation terms.

arXiv comment30 pages, 8 figures

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• Resummed Kinetic Field Theory: general formalism and linear structure growth from Newtonian particle dynamics
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• Local clustering of relic neutrinos with kinetic field theory
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• Kinetic Field Theory for Cosmic Structure Formation
• On the asymptotic behaviour of cosmic density-fluctuation power spectra of cold dark matter
• Resummed Kinetic Field Theory: Using Mesoscopic Particle Hydrodynamics to Describe Baryonic Matter in a Cosmological Framework
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• Kinetic Field Theory applied to Vector-Tensor Gravity
• Kinetic Field Theory: Perturbation theory beyond first order
• Kinetic Field Theory: Cosmic Structure Formation and Fluctuation-Dissipation Relations
• Resummed Kinetic Field Theory: a model of coupled baryonic and dark matter
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• Kinetic field theory: Non-linear cosmic power spectra in the mean-field approximation
• Kinetic field theory: effects of modified gravity theories with screening mechanisms on non-linear cosmic density fluctuations
• Free Cosmic Density Bispectrum on Small Scales