Inflation and the scale dependent spectral index: prospects and strategies

Adshead, Peter; Easther, Richard; Pritchard, Jonathan R.; Loeb, Abraham

doi:10.1088/1475-7516/2011/02/021

Cited by 164 publications

(185 citation statements)

References 92 publications

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“…However, because the running is second order in slow-roll, we expect it to be small, α s ∼ (n s − 1) 2 . Current bounds on α s are still two orders of magnitude larger than this target, but future galaxy surveys may allow such a measurement [157] (see also [158]). Any detection of a larger level of running would be a challenge for slow-roll inflation and would require additional physics to explain.…”

Section: Scalar Tilt and Runningmentioning

confidence: 98%

“…largest and smallest) eigenvalues of a random matrix. For a large class of random matrix ensembles, including the W W W ensemble [469], one finds [470][471][472] 158) where the function Ψ(ζ), which depends on the particular ensemble and is computable in simple cases, is N -independent at leading order in large N . In summary, eigenvalue repulsion dictates that the probability that a Hessian matrix in the ensemble defined by (3.149) has only positive eigenvalues is given by…”

Section: Random Supergravitymentioning

confidence: 99%

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Inflation and String Theory

2015

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Section: Scalar Tilt and Runningmentioning

confidence: 98%

Section: Random Supergravitymentioning

confidence: 99%

Inflation and String Theory

2015

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“…They are well described by a simple power-law spectrum, whose slope is consistent with a single scalar field driving inflation while slowly rolling down a very flat potential [8,9]. Proposed experiments like EUCLID [10] and PRISM [11] will measure the inflationary parameters even more precisely, and possibly extract additional quantities, such as the running of the scalar tilt [12]. This should further constrain the form of the inflaton potential during the quasi-de-Sitter phase.…”

Section: Introductionmentioning

confidence: 99%

Primordial non-gaussianity from the bispectrum of 21-cm fluctuations in the dark ages

2015

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A measurement of primordial non-gaussianity will be of paramount importance to distinguish between different models of inflation. Cosmic microwave background (CMB) anisotropy observations have set unprecedented bounds on the non-gaussianity parameter fNL but the interesting regime fNL 1 is beyond their reach. Brightness-temperature fluctuations in the 21-cm line during the dark ages (z ∼ 30 − 100) are a promising successor to CMB studies, giving access to a much larger number of modes. They are, however, intrinsically non-linear, which results in secondary non-gaussianities orders of magnitude larger than the sought-after primordial signal. In this paper we carefully compute the primary and secondary bispectra of 21-cm fluctuations on small scales. We use the flat-sky formalism, which greatly simplifies the analysis, while still being very accurate on small angular scales. We show that the secondary bispectrum is highly degenerate with the primordial one, and argue that even percent-level uncertainties in the amplitude of the former lead to a bias of order ∆fNL ∼ 10. To tackle this problem we carry out a detailed Fisher analysis, marginalizing over the amplitudes of a few smooth redshift-dependent coefficients characterizing the secondary bispectrum. We find that the signal-to-noise ratio for a single redshift slice is reduced by a factor of ∼ 5 in comparison to a case without secondary non-gaussianities. Setting aside foreground contamination, we forecast that a cosmic-variance-limited experiment observing 21-cm fluctuations over 30 ≤ z ≤ 100 with a 0.1-MHz bandwidth and 0.1-arcminute angular resolution could achieve a sensitivity of order f local NL ∼ 0.03, f equil NL ∼ 0.04 and f ortho NL ∼ 0.03.

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“…The approach we use here was discussed in Refs. [12][13][14][15][16] and applied postPlanck to power-law potentials in Ref. [17].…”

Section: Introductionmentioning

confidence: 99%

Equation-of-state parameter for reheating

2015

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Constraints to the parameters of inflation models are often derived assuming some plausible range for the number-e.g., N k = 46 to N k = 60-of e-folds of inflation that occurred between the time that our current observable Universe exited the horizon and the end of inflation. However, that number is, for any specific inflaton potential, related to an effective equation-of-state parameter wre and temperature Tre, for reheating. Although the physics of reheating is highly uncertain, there is a finite range of reasonable values for wre. Here we show that by restricting wre to this range, more stringent constraints to inflation-model parameters can be derived than those obtained from the usual procedure. To do so, we focus in this work in particular on natural inflation and inflation with a Higgs-like potential, and on power law models as limiting cases of those. As one example, we show that the lower limit to the tensor-to-scalar ratio r, derived from current measurements of the scalar spectral index, is about 20%-25% higher (depending on the model) with this procedure than with the usual approach.

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Inflation and the scale dependent spectral index: prospects and strategies

Cited by 164 publications

References 92 publications

Inflation and String Theory

Inflation and String Theory

Primordial non-gaussianity from the bispectrum of 21-cm fluctuations in the dark ages

Equation-of-state parameter for reheating

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