Lattice simulations of axion-U(1) inflation

Caravano, Angelo; Komatsu, Eiichiro; Lozanov, Kaloian D.; Weller, J.

doi:10.1103/physrevd.108.043504

Cited by 29 publications

(21 citation statements)

References 75 publications

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“…The study of Ref. [45] was able to capture the first oscillation of the inflaton velocity, whose shape agrees with that found in the works with a homogeneous inflaton. More recently, Ref.…”

Section: Discussionsupporting

confidence: 84%

“…3 The lattice simulations conducted in Ref. [45] yielded results for the inflaton power spectrum and bispectrum in the weak-backreaction regime, which exhibited excellent agreement with the analytical computations of Refs. [18,55].…”

Section: Introductionsupporting

confidence: 67%

“…[18,55]. However, the findings from the numerical studies [2,34,[37][38][39][40][41][42][43][44][45][46] of the strong-backreaction regime contradicted the analytical expectations. It was discovered that the evolution of the inflaton does not occur in a steady-state regime; instead, the parameter ξ (t) undergoes large oscillations, with a period of approximately ∼ 5 e-folds, around the steady-state analytical solution.…”

Section: Introductionmentioning

confidence: 88%

“…While all these studies assumed a homogeneous inflaton, the equations for a gauge field coupled to a spacetime-dependent inflaton were studied in Refs. [45,46] on the lattice. 3 The lattice simulations conducted in Ref.…”

Section: Introductionmentioning

confidence: 99%

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Axion inflation in the strong-backreaction regime: decay of the Anber-Sorbo solution

von Eckardstein,

Peloso,

Schmitz

et al. 2023

J. High Energ. Phys.

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Axion inflation coupled to Abelian gauge fields via a Chern-Simons-like term of the form $$ \phi F\overset{\sim }{F} $$ ϕF F ~ represents an attractive inflationary model with a rich phenomenology, including the production of magnetic fields, black holes, gravitational waves, and the matter-antimatter asymmetry. In this work, we focus on a particular regime of axion inflation, the so-called Anber-Sorbo (AS) solution, in which the energy loss in the gauge-field production provides the dominant source of friction for the inflaton motion. We revisit the AS solution and confirm that it is unstable. Contrary to earlier numerical works that attempted to reach the AS solution starting from a regime of weak backreaction, we perform, for the first time, a numerical evolution starting directly from the regime of strong backreaction. Our analysis strongly suggests that, at least as long as one neglects spatial inhomogeneities in the inflaton field, the AS solution has no basin of attraction, not even a very small one that might have been missed in previous numerical studies. Our analysis employs an arsenal of analytical and numerical techniques, some established and some newly introduced, including (1) linear perturbation theory along the lines of ref. [1], (2) the gradient expansion formalism (GEF) developed in ref. [2], (3) a new linearized version of the GEF, and (4) the standard mode-by-mode approach in momentum space in combination with input from the GEF. All these methods yield consistent results confirming the instability of the AS solution, which renders the dynamics of axion inflation in the strong-backreaction regime even more interesting than previously believed.

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“…The study of Ref. [45] was able to capture the first oscillation of the inflaton velocity, whose shape agrees with that found in the works with a homogeneous inflaton. More recently, Ref.…”

Section: Discussionsupporting

confidence: 84%

Section: Introductionsupporting

confidence: 67%

Section: Introductionmentioning

confidence: 88%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Axion inflation in the strong-backreaction regime: decay of the Anber-Sorbo solution

von Eckardstein,

Peloso,

Schmitz

et al. 2023

J. High Energ. Phys.

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“…This can avoid the possible presence of additional resonances and instabilities. These latter effects have been, for instance, explicitly seen in the context of axion inflation [19,26,27], where oscillatory features have been found in the inflaton velocity and the gauge-field spectrum, as a result of a nonlocal response. On the other hand, locality will allow us to obtain an analytic description of the dynamics of the perturbations [20].…”

Section: Local Response and Hierarchiesmentioning

confidence: 95%

Dissipative inflation via scalar production

Creminelli,

Kumar,

Salehian

et al. 2023

J. Cosmol. Astropart. Phys.

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We describe a new mechanism that gives rise to dissipation during cosmic inflation. In the simplest implementation, the mechanism requires the presence of a massive scalar field with a softly-broken global U(1) symmetry, along with the inflaton field. Particle production in this scenario takes place on parametrically sub-horizon scales, at variance with the case of dissipation into gauge fields. Consequently, the backreaction of the produced particles on the inflationary dynamics can be treated in a local manner, allowing us to compute their effects analytically. We determine the parametric dependence of the power spectrum which deviates from the usual slow-roll expression. Non-Gaussianities are always sizeable whenever perturbations are generated by the noise induced by dissipation: f NL eq ≳ O(10).

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Cosmological correlators through the looking glass: reality, parity, and factorisation

Stefanyszyn,

Tong,

Zhu

2024

J. High Energ. Phys.

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We consider the evolution of quantum fields during inflation, and show that the total-energy singularities appearing in the perturbative expansion of the late-time Wavefunction of the Universe are purely real when the external states are massless scalars and massless gravitons. Our proof relies on the tree-level approximation, Bunch-Davies initial conditions, and exact scale invariance (IR-convergence), but without any assumptions on invariance under de Sitter boosts. We consider all n-point functions and allow for the exchange of additional states of any mass and integer spin. Our proof makes use of a decomposition of the inflationary bulk-bulk propagator of massive spinning fields which preserves UV-convergence and ensures that the time-ordered contributions are purely real after we rotate to Euclidean time. We use this reality property to show that the maximally-connected parts of wavefunction coefficients, from which total-energy singularities originate, are purely real. In a theory where all states are in the complementary series, this reality extends to the full wavefunction coefficient. We then use our reality theorem to show that parity-odd correlators (correlators that are mirror asymmetric) are factorised and do not diverge when the total-energy is conserved. We pay special attention to the parity-odd four-point function (trispectrum) of inflationary curvature perturbations and use our reality/factorisation theorems to show that this observable is factorised into a product of cubic diagrams thereby enabling us to derive exact shapes. We present examples of couplings between the inflaton and massive spin-1 and spin-2 fields, with the parity-violation in the trispectrum driven by Chern-Simons corrections to the spinning field two-point function, or from parity-violating cubic interactions which we build within the Effective Field Theory of Inflation. In addition, we present a first-of-its-kind example of a parity-violating trispectrum, generated at tree-level, that arises in a purely scalar theory where the inflaton mixes linearly with an additional massive scalar field.

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Lattice simulations of axion-U(1) inflation

Cited by 29 publications

References 75 publications

Axion inflation in the strong-backreaction regime: decay of the Anber-Sorbo solution

Axion inflation in the strong-backreaction regime: decay of the Anber-Sorbo solution

Dissipative inflation via scalar production

Cosmological correlators through the looking glass: reality, parity, and factorisation

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