2006/11/30 by Patrick Valageas · 1 citation
Mathematics · Physics and Astronomy · #Action (physics) #Amplitude #Asymptotic expansion #Classical mechanics #Cluster analysis #Correlation function (quantum field theory) #Cosmology and Gravitation Theories #Galaxies: Formation, Evolution, Phenomena #Gaussian #Gradient descent #Gravitation #Mathematical analysis #Mathematics #Particle physics theoretical and experimental studies #Path integral formulation #Physics #Quantum mechanics #Series expansion #Statistical physics #astro-ph
paper · pdf · doi:10.1051/0004-6361:20066832
published as Astron. Astrophys. (2007), 465, 725 · 27 pages, published in A&A
openalex publication_date 2007/02/05 · arxiv created 2007/06/19 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We develop a path-integral formalism to study the formation of large-scale structures in the universe. Starting from the equations of motion of hydrodynamics (single-stream approximation) we derive the action which describes the statistical properties of the density and velocity fields for Gaussian initial conditions. Then, we present large-N expansions (associated with a generalization to N fields or with a semi-classical expansion) of the path-integral defined by this action. This provides a systematic expansion for two-point functions such as the response function and the usual two-point correlation. We present the results of two such expansions (and related variants) at one-loop order for a SCDM and a ΛCDM cosmology. We find that the response function exhibits fast oscillations in the non-linear regime with an amplitude which either follows the linear prediction (for the direct steepest-descent scheme) or decays (for the 2PI effective action scheme). On the other hand, the correlation function agrees with the standard one-loop result in the quasi-linear regime and remains well-behaved in the highly non-linear regime. This suggests that these large-N expansions could provide a good framework to study the dynamics of gravitational clustering in the non-linear regime. Moreover, the use of various expansion schemes allows one to estimate their range of validity without the need of N-body simulations and could provide a better accuracy in the weakly non-linear regime.