Effective Theory of Squeezed Correlation Functions

Abstract

Various inflationary scenarios can often be distinguished from one another by looking at the squeezed limit behavior of correlation functions. Therefore, it is useful to have a framework designed to study this limit in a more systematic and efficient way. We propose using an expansion in terms of weakly coupled super-horizon degrees of freedom, which is argued to generically exist in a near de Sitter space-time. The modes have a simple factorized form which leads to factorization of the squeezed-limit correlation functions with power-law behavior in $k_{\mathrm{long}}/k_{\mathrm{short}}$. This approach reproduces the known results in single-, quasi-single-, and multi-field inflationary models. However, it is applicable even if, unlike the above examples, the additional degrees of freedom are not weakly coupled at sub-horizon scales. Stronger results are derived in two-field (or sufficiently symmetric multi-field) inflationary models. We discuss the observability of the non-Gaussian 3-point function in the large-scale structure surveys, and argue that the squeezed limit behavior has a higher detectability chance than equilateral behavior when it scales as $(k_{\mathrm{long}}/k_{\mathrm{short}}{)}^{\Delta }$ with $\Delta <1$ -- where local non-Gaussianity corresponds to $\Delta =0$.

19+6 pages

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Cited by in corpus (14)

• Non-Gaussianity as a Particle Detector
• Bootstrapping Inflationary Correlators in Mellin Space
• Partially Massless Fields During Inflation
• Soft de Sitter Effective Theory
• Tensor Squeezed Limits and the Higuchi Bound
• Strongly Coupled Quasi-Single Field Inflation
• Constraints on holographic multi-field inflation and models based on the Hamilton-Jacobi formalism
• Cosmic variance in inflation with two light scalars
• The hemispherical asymmetry from a scale-dependent inflationary bispectrum
• In-in formalism for the entropy of quantum fields in curved spacetimes
• The Separate Universe Approach to Soft Limits
• Large gauge transformation, Soft theorem, and Infrared divergence in inflationary spacetime
• Conservation of $\zeta$ with radiative corrections from heavy field
• Single-Field Inflation and the Local Ansatz: Distinguishability and Consistency