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Cosmological Perturbation Theory Using the FFTLog: Formalism and Connection to QFT Loop Integrals

6 Pith papers cite this work. Polarity classification is still indexing.

6 Pith papers citing it
abstract

We present a new method for calculating loops in cosmological perturbation theory. This method is based on approximating a $\Lambda$CDM-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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background 2 method 2

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years

2026 5 2024 1

representative citing papers

Multi-tracers, multi-surveys: a joint Fisher analysis of DESI+PFS

astro-ph.CO · 2026-04-28 · unverdicted · novelty 6.0 · 2 refs

A joint multi-tracer Fisher analysis of DESI and PFS cross-spectra calibrates bias parameters from data, improving forecasted constraints on fσ8 by 33%, neutrino mass by 80%, and Ωm by 49% compared to single-tracer baselines.

SubTropica

hep-th · 2026-04-22 · unverdicted · novelty 5.0

SubTropica is a software package that automates symbolic integration of linearly-reducible Euler integrals via tropical subtraction, supported by HyperIntica and an AI-driven Feynman integral database.

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