Planck 2015. XX. Constraints on inflation

By P. Ade, N. Aghanim, M. Arnaud, F. Arroja, M. Ashdown, J. Aumont, C. Baccigalupi, M. Ballardini, A. Banday, Rita Belén Barreiro and 236 more. 2015

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We analyse the implications of the Planck data for cosmic inflation. The Planck nominal mission temperature anisotropy measurements, combined with the WMAP large-angle polarization, constrain the scalar spectral index to $n_s = 0.9603 \pm 0.0073$, ruling out exact scale invariance at over 5 $\sigma$. Planck establishes an upper bound on the tensor-to-scalar ratio of r 2 do not provide a good fit to the data. Planck does not find statistically significant running of the scalar spectral index, obtaining $d n_s/d ln k = -0.0134 \pm 0.0090$. Several analyses dropping the slow-roll approximation are carried out, including detailed model comparison and inflationary potential reconstruction. We also investigate whether the primordial power spectrum contains any features. We find that models with a parameterized oscillatory feature improve the fit $\chi^2$ by ~ 10; however, Bayesian evidence does not prefer these models. We constrain several single-field inflation models with generalized Lagrangians by combining power spectrum data with bounds on $f_\mathrm{NL}$ measured by Planck. The fractional primordial contribution of CDM isocurvature modes in the curvaton and axion scenarios has upper bounds of 0.25% or 3.9% (95% CL), respectively. In models with arbitrarily correlated CDM or neutrino isocurvature modes, an anticorrelation can improve $\chi^2$ by approximatively 4 as a result of slightly lowering the theoretical prediction for the $\ell<40$ multipoles relative to the higher multipoles. Nonetheless, the data are consistent with adiabatic initial conditions.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/da10d4d469098c3ce50aca8c2a17358a2045b5fe

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In Astronomy and Astrophysics

1. A. Banday
2. H. Eriksen
3. Volker Springel
4. Andrei Linde
5. F. Hansen
6. R. Kallosh
7. J. J. Carrasco
8. P. Lilje

In Atomic and Molecular Physics, and Optics

1. Andrei Linde
2. M. Miville-Deschênes
3. P. Martin
4. Torsten A. Ensslin
5. J. J. Carrasco
6. R. Kallosh
7. J. Chluba
8. H. Dole

In Statistical and Nonlinear Physics

1. Andrei Linde
2. R. Kallosh
3. Benjamin Dan Wandelt
4. A. Banday
5. J. J. Carrasco
6. M. Hobson
7. Jacques Delabrouille
8. M. Liguori