Markovian dynamics in de Sitter

Mirbabayi, Mehrdad

doi:10.1088/1475-7516/2021/09/038

Cited by 20 publications

(12 citation statements)

References 47 publications

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“…In the light physical mass regime and when the non-perturbativity is due to IR divergences both approaches should work. Then the eigenvalues of the Starobinski operator, computed to a subleading order in [3] (see also [105,106]), should manifest themselves as poles in the spectral density, discussed in the appendix C, for iν ∈ (0, d 2 ). In [77] we will show that it is indeed the case, providing an interesting check of both techniques.…”

Section: Summary and Future Directionsmentioning

confidence: 99%

Analyticity and unitarity for cosmological correlators

Pietro

Gorbenko

Komatsu

2022

J. High Energ. Phys.

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We study the fundamentals of quantum field theory on a rigid de Sitter space. We show that the perturbative expansion of late-time correlation functions to all orders can be equivalently generated by a non-unitary Lagrangian on a Euclidean AdS geometry. This finding simplifies dramatically perturbative computations, as well as allows us to establish basic properties of these correlators, which comprise a Euclidean CFT. We use this to infer the analytic structure of the spectral density that captures the conformal partial wave expansion of a late-time four-point function, to derive an OPE expansion, and to constrain the operator spectrum. Generically, dimensions and OPE coefficients do not obey the usual CFT notion of unitarity. Instead, unitarity of the de Sitter theory manifests itself as the positivity of the spectral density. This statement does not rely on the use of Euclidean AdS Lagrangians and holds non-perturbatively. We illustrate and check these properties by explicit calculations in a scalar theory by computing first tree-level, and then full one- loop-resummed exchange diagrams. An exchanged particle appears as a resonant feature in the spectral density which can be potentially useful in experimental searches.

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Section: Summary and Future Directionsmentioning

confidence: 99%

Analyticity and unitarity for cosmological correlators

Pietro

Gorbenko

Komatsu

2022

J. High Energ. Phys.

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“…Notice that the terms proportional to Ω 4 can be recast as subleading corrections to the noise of ζ of the form Ω 2 ζ 2 . These terms have been recently studied [41,62,63] and we will leave their analysis to future work. Instead of finding a solution for P 2 , let us collect the terms in the PDF up to order…”

Section: Jhep05(2022)052mentioning

confidence: 99%

The hand-made tail: non-perturbative tails from multifield inflation

Achúcarro

Céspedes

Davis

et al. 2022

J. High Energ. Phys.

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It is becoming increasingly clear that large but rare fluctuations of the primordial curvature field, controlled by the tail of its probability distribution, could have dramatic effects on the current structure of the universe — e.g. via primordial black-holes. However, the use of standard perturbation theory to study the evolution of fluctuations during inflation fails in providing a reliable description of how non-linear interactions induce non-Gaussian tails. Here, we use the stochastic inflation formalism to study the non-perturbative effects from multi-field fluctuations on the statistical properties of the primordial curvature field. Starting from the effective action describing multi-field fluctuations, we compute the joint probability density function and show that enhanced non-Gaussian tails are a generic feature of slow-roll inflation with additional degrees of freedom.

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“…An approach to deal with these IR effects has been known for a long time [224], but has not been developed systematically. For light scalars decoupled from gravity this was rectified in [225], and confirmed and extended using related but different techniques in [226][227][228][229][230][231]. The main conclusion is that strong IR effects are physical, can be controlled and calculated, and can lead to nonperturbative effects with observable consequences.…”

Section: Strong Ir Effectsmentioning

confidence: 69%

Snowmass White Paper: Cosmology at the Theory Frontier

Flauger¹,

Gorbenko²,

Joyce³

et al. 2022

Preprint

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The precision cosmological model describing the origin and expansion history of the universe, with observed structure seeded at the inflationary cosmic horizon, demands completion in the ultraviolet and in the infrared. The dynamics of the cosmic horizon also suggests an associated entropy, again requiring a microphysical theory. Recent years have seen enormous progress in understanding the structure of de Sitter space and inflation in string theory, and of cosmological observables captured by quantum field theory and solvable deformations thereof. The resulting models admit ongoing observational tests through measurements of the cosmic microwave background and large-scale structure, as well as through analyses of theoretical consistency by means of thought experiments. This paper, prepared for the TF01 and TF09 conveners of the Snowmass 2021 process, provides a synopsis of this important area, focusing on ongoing developments and opportunities.

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Markovian dynamics in de Sitter

Cited by 20 publications

References 47 publications

Analyticity and unitarity for cosmological correlators

Analyticity and unitarity for cosmological correlators

The hand-made tail: non-perturbative tails from multifield inflation

Snowmass White Paper: Cosmology at the Theory Frontier

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