Reply to Reyes et al

Carmo, Thomas A.; Filho, Nivaldo Menezes Filgueiras; Andrade, Bruno B.; Akrami, Kevan

doi:10.1093/cid/ciaa1142

Cited by 19 publications

(31 citation statements)

References 3 publications

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“…With regard to the inflationary era observational quantities, we shall be interested in the spectral index of the primordial scalar curvature perturbations n S , the tensor-to-scalar ratio r, and the tensor spectral index which for the theoretical framework at hand are given in equations ( 29), ( 33) and ( 34) respectively. Recall that the scalar spectral index and the tensor-to-scalar ratio are constrained by the 2018 Planck data [61] as follows,…”

Section: Confrontation With Observations: a Power-law Einstein-gauss-...mentioning

confidence: 99%

A refined Einstein–Gauss–Bonnet inflationary theoretical framework

Oikonomou

2021

Class. Quantum Grav.

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We provide a refined and much more simplified Einstein–Gauss–Bonnet inflationary theoretical framework, which is compatible with the GW170817 observational constraints on the gravitational wave speed. As in previous works, the constraint that the gravitational wave speed is in natural units, results to a constraint differential equation that relates the coupling function of the scalar field to the Gauss–Bonnet invariant ξ(ϕ) and the scalar potential V(ϕ). Adopting the slow-roll conditions for the scalar field and the Hubble rate, and in contrast to previous works, by further assuming that , which is motivated by slow-roll arguments, we succeed in providing much more simpler expressions for the slow-roll indices and for the tensor and scalar spectral indices and for the tensor-to-scalar ratio. We exemplify our refined theoretical framework by using an illustrative example with a simple power-law scalar coupling function ξ(ϕ) ∼ ϕ ν and as we demonstrate the resulting inflationary phenomenology is compatible with the latest Planck data. Moreover, this particular model produces a blue-tilted tensor spectral index, so we discuss in brief the perspective of describing the NANOGrav result with this model as is indicated in the recent literature.

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Section: Confrontation With Observations: a Power-law Einstein-gauss-...mentioning

confidence: 99%

A refined Einstein–Gauss–Bonnet inflationary theoretical framework

Oikonomou

2021

Class. Quantum Grav.

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“…Specifically, in this work we shall consider the class known as universal attractors [70], and we shall investigate the implications of such non-minimally coupled scalar field theories on static NSs in the Einstein frame. These models are known to provide a uniform inflationary phenomenology and belong to the larger class of cosmological attractors, which provide a viable inflationary phenomenology compatible with the latest Planck data [101]. We shall solve numerically the Tolman-Oppenheimer-Volkoff (TOV) equations, using an 'LSODA' integrator python 3 based code, which is a modification of [102], and with regard to the EoS for the nuclear matter, we shall assume that the EoS is a piecewise polytropic EoS [103,104], with the low density part being the WFF1 [105], the SLy [106], of the APR EoS [107].…”

Section: Introductionmentioning

confidence: 99%

Universal inflationary attractors implications on static neutron stars

Oikonomou¹

2021

Class. Quantum Grav.

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We study static neutron stars in the context of a class of non-minimally coupled inflationary potentials, the universal attractors. Universal attractors are known to generate a viable inflationary era, and they fall into the same category of inflationary phenomenology as the R 2 model and other well-known cosmological attractors. We present the essential features of universal attractors in both the Einstein and Jordan frame, and we extract the Tolman-Oppenheimer-Volkoff equations in the Einstein frame using the usual notation of theoretical astrophysics. We use a python 3 based double shooting numerical code for our numerical analysis and we construct the M-R graphs for the universal attractor potential, using piecewise polytropic equation of state the small density part of which is the WFF1 or the APR or the SLy equation of state. As we show, all the studied cases predict larger maximum masses for the neutron stars, and all the results are compatible with the GW170817 constraints imposed on the radii of the neutron stars.

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“…To verify the accuracy and consistency of any inflationary models, it is required to compare theoretical predictions with observations, e.g. [103][104][105]. In this regard, the dissipative coefficient must be specified, which can be considered as a function of the scalar field, or in more general cases, it could be a function of both the scalar field and fluid temperature.…”

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confidence: 99%

Warm tachyon inflation and swampland criteria *

et al. 2020

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In this study, the scenario of a two-component warm tachyon inflation is considered, where the tachyon field plays the role of the inflaton by driving the inflation. During inflation, the tachyon scalar field interacts with the other component of the Universe, which is assumed to be photon gas, i.e., radiation. The interacting term contains a dissipation coefficient, and the study is modeled based on two different and familiar choices of the coefficient that were studied in the literature. By employing the latest observational data, the acceptable ranges for the free parameters of the model are obtained. For any choice within the estimated ranges, there is an acceptable concordance between the theoretical predictions and observations. Although the model is established based on several assumptions, it is crucial to verify their validity for the obtained values of the free parameters of the model. It is found that the model is not self-consistent for all values of the ranges, and for some cases, the assumptions are violated. Therefore, to achieve both self-consistency and agreement with the data, the parameters of the model must be constrained. Subsequently, we consider the recently proposed swampland conjecture, which imposes two conditions on the inflationary models. These criteria rule out some inflationary models; however, warm inflation is among those that successfully satisfy the swampland criteria. We conduct a precise investigation, which indicates that the proposed warm tachyon inflation cannot satisfy the swampland criteria for some cases. In fact, for the first case of the dissipation coefficient, in which, there is dependency only on the scalar field, the model agrees with observational data. However, it is in direct tension with the swampland criteria. Nevertheless, for the second case, wherein the dissipation coefficient has a dependency on both the scalar field and temperature, the model exhibits acceptable agreement with observational data, and suitably satisfies the swampland criteria.

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Reply to Reyes et al

Cited by 19 publications

References 3 publications

A refined Einstein–Gauss–Bonnet inflationary theoretical framework

A refined Einstein–Gauss–Bonnet inflationary theoretical framework

Universal inflationary attractors implications on static neutron stars

Warm tachyon inflation and swampland criteria *

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