Eur. Phys. J. C (2019) 79: 1038
https://doi.org/10.1140/epjc/s10052-019-7571-0

Regular Article - Theoretical Physics

Constraining chameleon field driven warm inflation with Planck 2018 data

¹ School of Astronomy, Institute for Research in Fundamental Sciences (IPM), P. O. Box 19395-5531, Tehran, Iran
² Center for Space Research, North-West University, Mafikeng, South Africa
³ Department of Physics, Faculty of Science, University of Kurdistan, Sanandaj, Iran
⁴ Dipartimento di Fisica e Astronomia, Università di Bologna, via Irnerio 46, 40126, Bologna, Italy
⁵ Sanandaj Branch, Islamic Azad University, Sanandaj, Iran
⁶ Department of Physics, Babes-Bolyai University, Kogalniceanu Street, 400084, Cluj-Napoca, Romania
⁷ School of Physics, Sun Yat-Sen University, Xingang Road, Guangzhou, 510275, People’s Republic of China
⁸ Instituto de Física, Pontificia Universidad de Católica de Valparaíso, Casilla 4950, Valparaiso, Chile
⁹ Research Institute for Astronomy and Astrophysics of Maragha (RIAAM), P.O. Box 55134-441, Maragha, Iran
¹⁰ International Institute for Applicable Mathematics and Information Sciences (IIAMIS), B.M. Birla Science Centre, Adarsh Nagar, Hyderabad, 500 463, India

^* e-mail: h.sh.ahmadi@gmail.com
^** e-mail: h.sheikhahmadi@ipm.ir

Received: 27 August 2019
Accepted: 17 December 2019
Published online: 30 December 2019

Abstract

We investigate warm inflationary scenario in which the accelerated expansion of the early Universe is driven by chameleon-like scalar fields. Due to the non-minimal coupling between the scalar field and the matter sector, the energy-momentum tensor of each fluid component is not conserved anymore, and the generalized balance equation is obtained. The new source term in the energy equation can be used to model warm inflation. On the other hand, if the coupling function varies slowly, the model reduces to the standard model used for the description of cold inflation. To test the validity of the warm chameleon inflation model, the results for warm inflationary scenarios are compared with the observational Planck2018 Cosmic Microwave Background data. In this regard, the perturbation parameters such as the amplitude of scalar perturbations, the scalar spectral index and the tensor-to-scalar ratio are derived at the horizon crossing in two approximations, corresponding to the weak and strong dissipative regimes. As a general result it turns out that the theoretical predictions of the chameleon warm inflationary scenario are consistent with the Planck 2018 observations.