Divergence of perturbation theory in large scale structures

Enrico Pajer, Drian Van Der Woude

Research output: Contribution to journalArticleAcademicpeer-review


We make progress towards an analytical understanding of the regime of validity of perturbation theory for large scale structures and the nature of some non-perturbative corrections. We restrict ourselves to 1D gravitational collapse, for which exact solutions before shell crossing are known. We review the convergence of perturbation theory for the power spectrum, recently proven by McQuinn and White [1], and extend it to non-Gaussian initial conditions and the bispectrum. In contrast, we prove that perturbation theory diverges for the real space two-point correlation function and for the probability density function (PDF) of the density averaged in cells and all the cumulants derived from it. We attribute these divergences to the statistical averaging intrinsic to cosmological observables, which, even on very large and "perturbative" scales, gives non-vanishing weight to all extreme fluctuations. Finally, we discuss some general properties of non-perturbative effects in real space and Fourier space.

Original languageEnglish
Article number039
JournalJournal of Cosmology and Astroparticle Physics
Issue number5
Publication statusPublished - 14 May 2018


  • cosmic flows
  • cosmological parameters from LSS
  • cosmological perturbation theory
  • power spectrum


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