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Abstract: We present constraints on canonical single-field inflation derived from WMAPfive year, ACBAR, QUAD, BICEP data combined with the halo power spectrum fromSDSS LRG7. Models with a non-scale-invariant spectrum and a red tilt n s < 1are now preferred over the Harrison-Zel-dovich model n s = 1, tensor-to-scalarratio r = 0 at high significance. Assuming no running of the spectral indices,we derive constraints on the parameters n s, r and compare our results withthe predictions of simple inflationary models. The marginalised credibleintervals read n s = 0.962^{+0.028} {-0.026} and r < 0.17 at 95% confidencelevel. Interestingly, the 68% c.l. contours favour mainly models with a convexpotential in the observable region, but the quadratic potential model remainsinside the 95% c.l. contours. We demonstrate that these results are robust tochanges in the datasets considered and in the theoretical assumptions made. Wethen consider a non-vanishing running of the spectral indices by employingdifferent methods, non-parametric but approximate, or parametric but exact.With our combination of CMB and LSS data, running models are preferred overpower-law models only by a Delta chi^2 ~ 5.8, allowing inflationary stagesproducing a sizable negative running -0.063^{+0.061} {-0.049} and largertensor-scalar ratio r < 0.33 at the 95% c.l. This requires large values of thethird derivative of the inflaton potential within the observable range. Wederive bounds on this derivative under the assumption that the inflatonpotential can be approximated as a third order polynomial within the observablerange.



Author: Fabio Finelli, Jan Hamann, Samuel M. Leach, Julien Lesgourgues

Source: https://arxiv.org/



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