Effect of transitions in the Planck mass during inflation on primordial power spectra

Ashoorioon, Amjad; Bruck, Carsten van de; Millington, Peter; Vu, Susan

doi:10.1103/physrevd.90.103515

Cited by 19 publications

(10 citation statements)

References 176 publications

(190 reference statements)

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“…Expressions (9) have been shown to be in very good agreement with the numerical results calculated using the Mukhanov-Sasaki formalism even for models that do not obey the usual slow-roll conditions ( V , |η V | 1) [18]. Significant inaccuracies may occur if inflation is interrupted by a brief period of fast roll, causing a feature in the scalar power spectrum [19,20]. This situation does not occur in our present investigation.…”

Section: Of 14supporting

confidence: 80%

Primordial Gravitational Waves and Reheating in a New Class of Plateau-Like Inflationary Potentials

Chongchitnan

2018

Universe

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Abstract:We study a new class of inflation model parametrized by the Hubble radius, such that aH ∝ exp(−αφ) n . These potentials are plateau-like, and reduce to the power-law potentials in the simplest case n = 2. We investigate the range of model parameters that is consistent with current observational constraints on the scalar spectral index and the tensor-to-scalar ratio. The amplitude of primordial gravitational waves in these models is shown to be accessible by future laser interferometers such as DECIGO. We also demonstrate how these observables are affected by the temperature and equation of state during reheating. We find that a large subset of this model can support instantaneous reheating, as well as very low reheating temperatures of order a few MeV, giving rise to interesting consequences for dark-matter production.

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Section: Of 14supporting

confidence: 80%

Primordial Gravitational Waves and Reheating in a New Class of Plateau-Like Inflationary Potentials

Chongchitnan

2018

Universe

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“…This implies either a relatively large 3 or s 2 (or both). This can be achieved in models which violate slow-roll, such as those in which the potential has features, for example, if the first and second derivatives of and c s are small and only higher derivatives are large (the type of models studied in [20][21][22] are not in this class of models). This would likely require fine tuning of the coefficients of the lower order terms in the effective potential.…”

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confidence: 99%

Running of the running and entropy perturbations during inflation

Bruck

Longden

2016

Phys. Rev. D

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In single field slow-roll inflation, one expects that the spectral index n s − 1 is first order in slow-roll parameters. Similarly, its running α s ¼ dn s =d log k and the running of the running β s ¼ dα s =d log k are second and third order and therefore expected to be progressively smaller, and usually negative. Hence, such models of inflation are in considerable tension with a recent analysis hinting that β s may actually be positive, and larger than α s . Motivated by this, in this work we ask the question of what kinds of inflationary models may be useful in achieving such a hierarchy of runnings, particularly focusing on twofield models of inflation in which the late-time transfer of power from isocurvature to curvature modes allows for a much more diverse range of phenomenology. We calculate the runnings due to this effect and briefly apply our results to assess the feasibility of finding jβ s j ≳ jα s j in some specific models. DOI: 10.1103/PhysRevD.94.021301 Constraining models of inflation is one of the most important goals of cosmology. By constraining or even ruling out models of inflation, cosmologists learn a great deal about model building in theories beyond the standard model. Even with the latest cosmological observations [1,2], there is still a plethora of inflationary models compatible with data [3]. It was recently pointed out that observations of the cosmic microwave background (CMB) radiation are consistent with a rather large running of the running of the spectral index, 1 [4,5]. The constraints on α s and β s given in [5] are α s ¼ 0.011 AE 0.010 and β s ¼ 0.027 AE 0.013 (fixing the pivot scale at k ¼ 0.05 Mpc −1 ), which implies β s > 0 at the 2σ confidence level and hints that the running of the running may be larger than the running itself. The running α s also appears to be positive (although less significantly), which leads to a slight tension with a wide range of inflationary models that predict a negative running [6]. Future CMB experiments are needed to determine these parameters more precisely, but given this first hint of what is potentially a powerful piece of evidence in early universe cosmology, it is interesting and worthwhile to consider the theoretical viability for such a hierarchy of runnings to be realized in inflation.In standard single field slow-roll models, the running is of second order in slow-roll parameters and the running of the running is third order [see Eqs. (5)- (7) below]. Thus, in such models of inflation, one would quite generally expect β s to be smaller than α s . These observational hints motivate the current work, in which we study predictions of α s and β s in single and two-field inflationary scenarios with the intention of understanding what kinds of inflationary models could be consistent with such a hierarchy of runnings.While almost all investigations of inflationary models make predictions for the spectral index, relatively few study the running [6][7][8][9], and almost none discuss the running of the running [4,10]. This is largely underst...

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“…To search for evidence, it is important to investigate the associated cosmological implications, in particular, applications to the very early universe and their observational consequences. In this sense, various theoretical models have been proposed to explain certain CMB anomalies such as step potentials [18,25,26,[35][36][37], transient sound speed reduction [27][28][29]38], massive fields [32,33,39], varying Planck mass models [40], pre-inflationary fast roll models [41], linear oscillations [30,31,42,43], logarithmic oscillations [44][45][46], and cutoff models [47][48][49].…”

Section: Discussionmentioning

confidence: 99%

Searching for features of a string-inspired inflationary model with cosmological observations

Cai

Ferreira

et al. 2015

Phys. Rev. D

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The latest Planck results show a power deficit in the temperature anisotropies near ≈ 20 in the cosmic microwave background (CMB). This observation can hardly be explained within the standard inflationary Λ-cold-dark-matter (ΛCDM) scenario. In this paper we consider a string theory inspired inflationary model (axion monodromy inflation) with a step-like modulation in the potential which gives rise to observable signatures in the primordial perturbations. One interesting phenomenon is that the primordial scalar modes experience a sudden suppression at a critical scale when the modulation occurs. By fitting to the CMB data, we find that the model can nicely explain the ≈ 20 power deficit anomaly as well as predict specific patterns in the temperature-polarization correlation and polarization autocorrelation spectra. Though the significance of the result is not sufficient to claim a detection, our analysis reveals that fundamental physics at extremely high energy scales, namely, some effects inspired by string theory, may be observationally testable in forthcoming cosmological experiments.

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Effect of transitions in the Planck mass during inflation on primordial power spectra

Cited by 19 publications

References 176 publications

Primordial Gravitational Waves and Reheating in a New Class of Plateau-Like Inflationary Potentials

Primordial Gravitational Waves and Reheating in a New Class of Plateau-Like Inflationary Potentials

Running of the running and entropy perturbations during inflation

Searching for features of a string-inspired inflationary model with cosmological observations

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