Testing <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si95.svg" display="inline" id="d1e11063"><mml:mi>α</mml:mi></mml:math>-attractor quintessential inflation against CMB and low-redshift data

Giarè, William; Di Valentino, Eleonora; Linder, Eric V.; Specogna, Enrico

doi:10.1016/j.dark.2024.101713

Physics of the Dark Universe

2024

DOI: 10.1016/j.dark.2024.101713

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Testing α-attractor quintessential inflation against CMB and low-redshift data

William Giarè,

Eleonora Di Valentino,

Eric V. Linder

et al.

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Cited by 2 publications

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Testing scale-invariant inflation against cosmological data

Cecchini,

De Angelis,

Giarè

et al. 2024

J. Cosmol. Astropart. Phys.

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There is solid theoretical and observational motivation behind the idea of scale-invariance as a fundamental symmetry of Nature. We consider a recently proposed classically scale-invariant inflationary model, quadratic in curvature and featuring a scalar field non-minimally coupled to gravity. We go beyond earlier analytical studies, which showed that the model predicts inflationary observables in qualitative agreement with data, by solving the full two-field dynamics of the system — this allows us to corroborate previous analytical findings and set robust constraints on the model's parameters using the latest Cosmic Microwave Background (CMB) data from Planck and BICEP/Keck. We demonstrate that scale-invariance constrains the two-field trajectory such that the effective dynamics are that of a single field, resulting in vanishing entropy perturbations and protecting the model from destabilization effects. We derive tight upper limits on the non-minimal coupling strength, excluding conformal coupling at high significance. By explicitly sampling over them, we demonstrate an overall insensitivity to initial conditions. We argue that the model predicts a minimal level of primordial tensor modes set by r ≳ 0.003, well within the reach of next-generation CMB experiments. These will therefore provide a litmus test of scale-invariant inflation, and we comment on the possibility of distinguishing the model from Starobinsky and α-attractor inflation. Overall, we argue that scale-invariant inflation is in excellent health, and possesses features which make it an interesting benchmark for tests of inflation from future CMB data.

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Testing scale-invariant inflation against cosmological data

Cecchini,

De Angelis,

Giarè

et al. 2024

J. Cosmol. Astropart. Phys.

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Robust preference for Dynamical Dark Energy in DESI BAO and SN measurements

Giarè,

Najafi,

Pan

et al. 2024

J. Cosmol. Astropart. Phys.

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Recent Baryon Acoustic Oscillation (BAO) measurements released by DESI, when combined with Cosmic Microwave Background (CMB) data from Planck and two different samples of Type Ia supernovae (Pantheon-Plus and DESY5) reveal a preference for Dynamical Dark Energy (DDE) characterized by a present-day quintessence-like equation of state that crossed into the phantom regime in the past. A core ansatz for this result is assuming a linear Chevallier-Polarski-Linder (CPL) parameterization w(a) = w 0 + wa (1-a) to describe the evolution of the DE equation of state (EoS). In this paper, we test if and to what extent this assumption impacts the results. To prevent broadening uncertainties in cosmological parameter inference and facilitate direct comparison with the baseline CPL case, we focus on 4 alternative well-known models that, just like CPL, consist of only two free parameters: the present-day DE EoS (w0 ) and a parameter quantifying its dynamical evolution (wa ). We demonstrate that the preference for DDE remains robust regardless of the parameterization: w0 consistently remains in the quintessence regime, while wa consistently indicates a preference for a dynamical evolution towards the phantom regime. This tendency is significantly strengthened by DESY5 SN measurements. By comparing the best-fit χ2 obtained within each DDE model, we notice that the linear CPL parameterization is not the best-fitting case. Among the models considered, the EoS proposed by Barboza and Alcaniz consistently leads to the most significant improvement.

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Testing α-attractor quintessential inflation against CMB and low-redshift data

Cited by 2 publications

References 80 publications

Testing scale-invariant inflation against cosmological data

Testing scale-invariant inflation against cosmological data

Robust preference for Dynamical Dark Energy in DESI BAO and SN measurements

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