Bootstrapping one-loop inflation correlators with the spectral decomposition

Xianyu, Zhong-Zhi; Zhang, Hongyu

doi:10.1007/jhep04(2023)103

Cited by 26 publications

(9 citation statements)

References 89 publications

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“…Practically, however, we can use numerical interpolation to bridge the gap between different regions. This strategy has been shown to be workable in previous studies [90]. So, barring possible issues of analytical continuation for special configurations, we can say that, the problem of analytical computation of arbitrary tree-level inflation correlators is solved, if we can compute the arbitrary nested time integral.…”

Section: Jhep03(2024)070mentioning

confidence: 97%

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Inflation correlators with multiple massive exchanges

Xianyu,

Zang

2024

J. High Energ. Phys.

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The most general tree-level boundary correlation functions of quantum fields in inflationary spacetime involve multiple exchanges of massive states in the bulk, which are technically difficult to compute due to the multi-layer nested time integrals in the Schwinger-Keldysh formalism. On the other hand, correlators with multiple massive exchanges are well motivated in cosmological collider physics, with the original quasi-single-field inflation model as a notable example. In this work, with the partial Mellin-Barnes representation, we derive a simple rule, called family-tree decomposition, for directly writing down analytical answers for arbitrary nested time integrals in terms of multi-variable hypergeometric series. We present the derivation of this rule together with many explicit examples. This result allows us to obtain analytical expressions for general tree-level inflation correlators with multiple massive exchanges. As an example, we present the full analytical results for a range of tree correlators with two massive exchanges.

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Section: Jhep03(2024)070mentioning

confidence: 97%

“…Many explicit analytical results have been obtained in recent years for inflation correlators relating to CC physics [63,64,70,71,[88][89][90][91][92][93]. Most of these results are for the exchange of a single massive particle in the bulk of dS, with a few exceptions at loop orders.…”

Section: Jhep03(2024)070mentioning

confidence: 99%

Inflation correlators with multiple massive exchanges

Xianyu,

Zang

2024

J. High Energ. Phys.

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“…For a momentum ratio beyond this cutoff scale, the resonance event cannot happen because the fermions would have paired and condensed due to the attractive self-interaction. The exact expression for the correlator is hard to calculate even at the tree-level [83][84][85] or for a bubble loop diagram [86], not to mention the triangle loop diagram here. Thus here we simply estimate the cosmological collider signal by the cumulated phase…”

Section: Jcap04(2024)022mentioning

confidence: 99%

BCS in the sky: signatures of inflationary fermion condensation

Tong,

Wang,

Zhang

et al. 2024

J. Cosmol. Astropart. Phys.

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We consider a Bardeen-Cooper-Schrieffer (BCS)-like model in the inflationary background. We show that with an axial chemical potential, the attractive quartic fermion self-interaction can lead to a BCS-like condensation. In the rigid-de Sitter (dS) limit of inflation where backreaction from the inflaton and graviton is neglected, we perform the first computation of the non-perturbative effective potential that includes the full spacetime curvature effects in the presence of the chemical potential, subject to the mean-field approximation whose validity has been checked via the Ginzburg criterion. The corresponding BCS phase transition is always first-order, when the varying Hubble is interpreted as an effective Gibbons-Hawking temperature of dS spacetime. In the condensed phase, the theory can be understood from UV and IR sides as fermionic and bosonic, respectively. This leads to distinctive signatures in the primordial non-Gaussianity of curvature perturbations. Namely, the oscillatory cosmological collider signal is smoothly turned off at a finite momentum ratio, since different momentum ratios effectively probe different energy scales. In addition, such BCS phase transitions can also source stochastic gravitational waves, which are feasible for future experiments.

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“…First, it does not involve logarithms or polylogarithms, as one might have expected from a loop diagram, but simply a rational function. This is enormously simpler than the more general parity-even one-loop contributions [17][18][19]. Second, the rational function has only a pole at k T = 0.…”

Section: Jhep11(2023)038mentioning

confidence: 99%

Leading loops in cosmological correlators

Lee,

McCulloch,

Pajer

2023

J. High Energ. Phys.

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Cosmological correlators from inflation are often generated at tree level and hence loop contributions are bounded to be small corrections by perturbativity. Here we discuss a scenario where this is not the case. Recently, it has been shown that for any number of scalar fields of any mass, the parity-odd trispectrum of a massless scalar must vanish in the limit of exact scale invariance due to unitarity and the choice of initial state. By carefully handling UV-divergences, we show that the one-loop contribution is non-vanishing and hence leading. Surprisingly, the one-loop parity-odd trispectrum is simply a rational function of kinematics, which we compute explicitly in a series of models, including single-clock inflation. Although the loop contribution is the leading term in the parity-odd sector, its signal-to-noise ratio is typically bounded from above by that of a corresponding tree-level parity-even trispectrum, unless instrumental noise and systematics for the two observables differ. Furthermore, we identify a series of loop contributions to the wavefunction that cancel exactly when computing correlators, suggesting a more general phenomenon.

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Bootstrapping one-loop inflation correlators with the spectral decomposition

Cited by 26 publications

References 89 publications

Inflation correlators with multiple massive exchanges

Inflation correlators with multiple massive exchanges

BCS in the sky: signatures of inflationary fermion condensation

Leading loops in cosmological correlators

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