Large-scale perturbations from the waterfall field in hybrid inflation

Fonseca, José; Sasaki, Misao; Wands, David

doi:10.1088/1475-7516/2010/09/012

Cited by 32 publications

(62 citation statements)

References 30 publications

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“…The case with φ 2 c < 12M 2 P is somewhat similar to standard hybrid inflation as studied in [7][8][9][10][11]. We shall come back to this limit in section VI.…”

mentioning

confidence: 75%

“…In comparison, in standard hybrid inflation this problem does not show up. As shown in recent analysis [7][8][9][10][11] the curvature perturbations from the waterfall field in standard hybrid inflation with φ c ≪ M P and κ ψ ≫ 1 scales like (k/k c ) 3 ∼ e −3Nc which is totally negligible on the cosmological scales.…”

Section: A Power Spectrum and Spectral Tiltmentioning

confidence: 90%

“…(2.7). For φ 2 c > 12M 2 P this leads to a period of chaotic inflation where φ evolves as 9) where φ p indicates the value of φ at the time of n p . As in chaotic inflation, inflation ends at φ = φ f where the slow-roll conditions are violated.…”

Section: Hybrid Inflation and Its Parameters Spacementioning

confidence: 99%

“…This should be compared with the standard hybrid inflation where it is found that n s ≃ 4 [7][8][9][10][11], a very blue-tilted spectrum. This is the key property which renders the curvature perturbations from the waterfall field harmless in standard hybrid inflation.…”

Section: A Power Spectrum and Spectral Tiltmentioning

confidence: 99%

“…As shown in [7][8][9][10][11] the induced curvature perturbation from the waterfall field is highly blue-tilted and is completely negligible on large scales. We would like to search the parameter space of hybrid inflation in general and examine the dynamics of waterfall phase transition and its contribution to power spectrum.…”

Section: General Parameter Space Of Hybrid Inflationmentioning

confidence: 99%

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Curvature perturbation and waterfall dynamics in hybrid inflation

Abolhasani

Firouzjahi

Sasaki

2011

J. Cosmol. Astropart. Phys.

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We investigate the parameter spaces of hybrid inflation model with special attention paid to the dynamics of waterfall field and curvature perturbations induced from its quantum fluctuations. Depending on the inflaton field value at the time of phase transition and the sharpness of the phase transition inflation can have multiple extended stages. We find that for models with mild phase transition the induced curvature perturbation from the waterfall field is too large to satisfy the COBE normalization. We investigate the model parameter space where the curvature perturbations from the waterfall quantum fluctuations vary between the results of standard hybrid inflation and the results obtained here.

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“…The case with φ 2 c < 12M 2 P is somewhat similar to standard hybrid inflation as studied in [7][8][9][10][11]. We shall come back to this limit in section VI.…”

mentioning

confidence: 75%

Section: A Power Spectrum and Spectral Tiltmentioning

confidence: 90%

Section: Hybrid Inflation and Its Parameters Spacementioning

confidence: 99%

Section: A Power Spectrum and Spectral Tiltmentioning

confidence: 99%

Section: General Parameter Space Of Hybrid Inflationmentioning

confidence: 99%

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Curvature perturbation and waterfall dynamics in hybrid inflation

Abolhasani

Firouzjahi

Sasaki

2011

J. Cosmol. Astropart. Phys.

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Natural hybrid inflation model with large non-Gaussianity

Choi

Kyae

2012

Physics Letters B

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We propose an inflationary model ("natural hybrid model"), which combines the supersymmetric hybrid model and the natural inflation model to achieve the spectral index of 0.96, and the axion decay constant smaller than the Planck scale, f ≪ M P . By introducing both U(1) R and a shift symmetry and employing the minimal Kähler potential, the eta-problem can be still avoided. The two inflaton fields in this model can admit large non-Gaussianity.Inflation [1] is known to be the best solution to the fine tuning problems associated with the initial conditions of the universe in the standard big bang cosmology: it resolves so-called the "homogeneity problem" and "flatness problem." Moreover, quantum fluctuation of the inflaton fields generated during inflation can eventually provide seeds of large scale structure (LSS) observed in our universe [2]. Thus, it has been tested by observing the fluctuations in the LSS, the temperature anisotropy in the cosmic microwave background (CMB), and so on through the satellite experiments such as COBE [3] and Wilkinson Microwave Anisotropy Probe (WMAP) [4] so far, and also will be more precisely checked by Planck [5] in the near future.The recent WMAP seven data [4] shows that the initial density perturbation is almost scale invariant and Gaussian with n ζ = 0.96 +0.014 −0.013 and −10 < f local NL < 74 at the 95% confidence level. The single field chaotic inflation is well consistent with the current observation, implying very small non-Gaussianity suppressed by the slow-roll parameters [6]. If sizable non-Gaussianity will be detected in Planck satellite experiment in the near future, however, it will play the role of the criterion to select a realistic inflationary model.Inflationary scenario is based on scalar field theory. Although inflationary scenario seems to be inevitable in cosmology, it is very non-trivial to realize in quantum field theory. In order to keep the small inflaton mass against quantum corrections, introduction of supersymmetry (SUSY) is helpful as in particle physics. Unless an inflationary model is not very elaborately constructed, however, introduction of SUSY is not enough: the positive vacuum energy in supergravity (SUGRA) induces the Hubble scale inflaton mass, yielding η ∼ O(1) during inflation, which destroys the slow-roll condition. It is called the "eta-problem.""Hybrid inflation" [7] is basically an two field model with one as inflaton and the other, called waterfall field, to terminate the inflation when it becomes tachyonic. The advantage of it is that the inflaton's field value is small compared to the Planck scale, and thus it is legitimate to use the low energy effective theory. In the SUSY version of hybrid inflation [8,9], the potential can be made flat enough, avoiding the eta-problem: fortunately the Hubble induced mass term is accidentally cancelled out with the minimal Kähler potential and the Polonyi type superpotential during inflation. The specific form of the superpotential can be guaranteed by the introduced U(1) R symmetry.By the log...

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A density spike on astrophysical scales from an N-field waterfall transition

et al. 2015

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Hybrid inflation models are especially interesting as they lead to a spike in the density power spectrum on small scales, compared to the CMB, while also satisfying current bounds on tensor modes.Here we study hybrid inflation with N waterfall fields sharing a global SO(N ) symmetry. The inclusion of many waterfall fields has the obvious advantage of avoiding topologically stable defects for N > 3.We find that it also has another advantage: it is easier to engineer models that can simultaneously (i) be compatible with constraints on the primordial spectral index, which tends to otherwise disfavor hybrid models, and (ii) produce a spike on astrophysically large length scales. The latter may have significant consequences, possibly seeding the formation of astrophysically large black holes. We calculate correlation functions of the time-delay, a measure of density perturbations, produced by the waterfall fields, as a convergent power series in both 1/N and the field's correlation function (x). We show that for large N , the two-point function is δt(x) δt(0) ∝ 2 (|x|)/N and the three-point function is δt(x) δt(y) δt(0) ∝ (|x − y|) (|x|) (|y|)/N 2 . In accordance with the central limit theorem, the density perturbations on the scale of the spike are Gaussian for large N and non-Gaussian for small N .

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Large-scale perturbations from the waterfall field in hybrid inflation

Cited by 32 publications

References 30 publications

Curvature perturbation and waterfall dynamics in hybrid inflation

Curvature perturbation and waterfall dynamics in hybrid inflation

Natural hybrid inflation model with large non-Gaussianity

A density spike on astrophysical scales from an N-field waterfall transition

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