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Register a new userObservational constraints on inflation with the nonlinear sigma fields in light of Plank 2015
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Added by
Gansukh Tumurtushaa
Publication date
2015
fields
Physics
and research's language is
English
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We study an inflation model with a nonlinear sigma field which has $SO(3)$ symmetry. The background solution of the nonlinear sigma field is proportional to the space coordinates linearly while keeping the homogeneous and isotropic background spacetime. We calculate the observable quantities including the power spectra of the scalar and tensor modes, the spectral indices, the tensor-to-scalar ratio, and the running of the spectral indices, and then constrain our model with the Planck 2015 observational data.
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The constraints on a general form of the power-law potential and the dissipation coefficient in the framework of warm single field inflation imposed by Planck data will be investigated. {By Considering a quasi-static Universe, besides a slow-roll condition, the suitable regions in which a pair of theoretical free parameters are in good agreement with Planck results will be estimated}. In this method instead of a set of free parameters, we can visualize a region of free parameters that can satisfy the precision limits on theoretical results. On the other side, when we consider the preformed quantity for the amplitude of scalar perturbations, the conflict between obtained results for free parameters in different steps dramatically will be decreased. {As have done in prominent} literature, based on the friction of the environment, we can divide the primordial Universe to the two different epochs namely weak and strong dissipative regimes. For the aforementioned eras, the free parameters of the model will be constrained and the best regions will be obtained. To do so, the main inflationary observables such as tensor-to-scalar ratio, power-spectra of density perturbations and gravitational waves, scalar and tensor spectral indices, running spectral index and the number of e-folds in both weak and strong regimes will be obtained. Ultimately, it can be visualized, this model can make concord between theoretical results and data originated from cosmic microwave background and Planck $2013$, $2015$ and $2018$.
We study slow-roll inflation with a Gauss-Bonnet term that is coupled to an inflaton field nonminimally. We investigate the inflationary solutions for a specific type of the nonminimal coupling to the Gauss-Bonnet term and inflaton potential both analytically and numerically. We also calculate the observable quantities such as the power spectra of the scalar and tensor modes, the spectral indices, the tensor-to-scalar ratio and the running spectral indices. Finally, we constrain our result with the observational data by Planck and BICEP2 experiment.
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For the constant-roll tachyon inflation, we derive the analytical expressions for the scalar and tensor power spectra, the scalar and tensor spectral tilts and the tensor to scalar ratio up to the first order by using the method of Bessel function approximation. The derived $n_s-r$ results for the constant-roll inflation are also compared with the observations, we find that only one constant-roll inflation is consistent with the observations and observations constrain the constant-roll inflation to be slow-roll inflation. The tachyon potential is also reconstructed for the constant-roll inflation which is consistent with the observations.
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