Journal
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
Volume -, Issue 4, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/1475-7516/2018/04/030
Keywords
power spectrum; baryon acoustic oscillations
Funding
- European Research Council [ERC-STG-639729]
- Institute for Advanced Study
- Raymond and Beverly Sackler Foundation
- NSF [AST-1409709, PHY-1521097]
- Canadian Institute for Advanced Research (CIFAR) program on Gravity and the Extreme Universe
- Division Of Physics
- Direct For Mathematical & Physical Scien [1521097] Funding Source: National Science Foundation
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We present a new method for calculating loops in cosmological perturbation theory. This method is based on approximating a ACDM-like cosmology as a finite sum of complex power-law universes. The decomposition is naturally achieved using an FFTLog algorithm. For power-law cosmologies, all loop integrals are formally equivalent to loop integrals of massless quantum field theory. These integrals have analytic solutions in terms of generalized hypergeometric functions. We provide explicit formulae for the one-loop and the two-loop power spectrum and the one-loop bispectrum. A chief advantage of our approach is that the difficult part of the calculation is cosmology independent, need be done only once, and can be recycled for any relevant predictions. Evaluation of standard loop diagrams then boils down to a simple matrix multiplication. We demonstrate the promise of this method for applications to higher multiplicity/loop correlation functions.
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