Stability analysis of chromo-natural inflation and possible evasion of Lyth’s bound

Dimastrogiovanni, Emanuela; Peloso, Marco

doi:10.1103/physrevd.87.103501

Cited by 143 publications

(281 citation statements)

References 105 publications

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“…A full analysis at linear order in perturbation theory was later presented in [33], where the model was found to be highly unstable in the sub-horizon regime for:…”

Section: Introductionmentioning

confidence: 99%

Gauge-flation confronted with Planck

Namba¹,

Dimastrogiovanni²,

Peloso³

2013

J. Cosmol. Astropart. Phys.

Self Cite

110

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Gauge-flation is a recently proposed model in which inflation is driven solely by a non-Abelian gauge field thanks to a specific higher order derivative operator. The nature of the operator is such that it does not introduce ghosts. We compute the cosmological scalar and tensor perturbations for this model, improving over an existing computation. We then confront these results with the Planck data. The model is characterized by the quantity γ ≡H 2 (where g is the gauge coupling constant, Q the vector vev, and H the Hubble rate). For γ < 2, the scalar perturbations show a strong tachyonic instability. In the stable region, the scalar power spectrum n s is too low at small γ, while the tensor-to-scalar ratio r is too high at large γ. No value of γ leads to acceptable values for n s and r, and so the model is ruled out by the CMB data. The same behavior with γ was obtained in Chromo-natural inflation, a model in which inflation is driven by a pseudo-scalar coupled to a non-Abelian gauge field. When the pseudo-scalar can be integrated out, one recovers the model of Gauge-flation plus corrections. It was shown that this identification is very accurate at the background level, but differences emerged in the literature concerning the perturbations of the two models. On the contrary, our results show that the analogy between the two models continues to be accurate also at the perturbative level.

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“…A full analysis at linear order in perturbation theory was later presented in [33], where the model was found to be highly unstable in the sub-horizon regime for:…”

Section: Introductionmentioning

confidence: 99%

Gauge-flation confronted with Planck

Namba¹,

Dimastrogiovanni²,

Peloso³

2013

J. Cosmol. Astropart. Phys.

Self Cite

110

View full text Add to dashboard Cite

show abstract

“…(13), t ij and h ij , are transverse, traceless, synchronous tensors, following Refs. [38,39]. Additionally, t ij and h ij are invariant under general covariance and SU(2) gauge transformations.…”

Section: A Tensorsmentioning

confidence: 99%

“…We are following Subsection III A of [38] for developing the perturbation quantities. In general there are 9 perturbation degrees of freedom for the gauge field and 6 in the metric sector.…”

Section: Perturbation Equationsmentioning

confidence: 99%

“…In this case, we may adopt the WKB approximation developed here in order to solve for the more slowly-evolving envelope of the wave amplitude. We write (38) and define ∆θ ≡ θ η − θ ν . The functions we have to determine are η, ν and ∆θ.…”

Section: Short Wavelengthsmentioning

confidence: 99%

“…Some of the perturbation quantities are defined as gradients of scalars, just as in general scalar-vector-tensor decompositions. To simplify notation and make some calculations easier, without loss of generality due to rotational invariance, the authors of [38] choose the Fourier wave vectors k to be oriented along the z direction. We follow that convention.…”

Section: Perturbation Equationsmentioning

confidence: 99%

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Cosmological consequences of classical flavor-space locked gauge field radiation

Bielefeld

Caldwell

2015

Phys. Rev. D

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We propose a classical SU(2) gauge field in a flavor-space locked configuration as a species of radiation in the early universe, and show that it would have a significant imprint on a primordial stochastic gravitational wave spectrum. In the flavor-space locked configuration, the electric and magnetic fields of each flavor are parallel and mutually orthogonal to other flavors, with isotropic and homogeneous stress-energy. Due to the non-Abelian coupling, the gauge field breaks the symmetry between left-and right-circularly polarized gravitational waves. This broken chiral symmetry results in a unique signal: non-zero cross correlation of the cosmic microwave background temperature and polarization, T B and EB, both of which should be zero in the standard, chiral symmetric case. We forecast the ability of current and future CMB experiments to constrain this model. Furthermore, a wide range of behavior is shown to emerge, depending on the gauge field coupling, abundance, and allocation into electric and magnetic field energy density. The fluctuation power of primordial gravitational waves oscillates back and forth into fluctuations of the gauge field. In certain cases, the gravitational wave spectrum is shown to be suppressed or amplified by up to an order of magnitude depending on the initial conditions of the gauge field.

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Boosting GWs in supersolid inflation

Celoria

Comelli

Pilo

et al. 2021

J. High Energ. Phys.

102

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Inflation driven by a generic self-gravitating medium is an interesting alternative to study the impact of spontaneous spacetime symmetry breaking during a quasi de-Sitter phase, in particular the 4-dimensional diffeomorphism invariance of GR is spontaneously broken down to I SO(3). The effective description is based on four scalar fields that describe the excitations of a supersolid. There are two phonon-like propagating scalar degrees of freedom that mix non-trivially both at early and late times and, after exiting the horizon, give rise to non-trivial correlations among the different scalar power spectra. The non-linear structure of the theory allows a secondary gravitational waves production during inflation, efficient enough to saturate the present experimental bound and with a blue-tilted spectral index.

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Stability analysis of chromo-natural inflation and possible evasion of Lyth’s bound

Cited by 143 publications

References 105 publications

Gauge-flation confronted with Planck

Gauge-flation confronted with Planck

Cosmological consequences of classical flavor-space locked gauge field radiation

Boosting GWs in supersolid inflation

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