http://arxiv.org/abs/2002.08269
We present a new class of non-singular bounce cosmology free from instabilities, using a single scalar field coupled to gravity within the framework of the Degenerate Higher-Order Scalar-Tensor (DHOST) theories. In this type of scenarios, the gradient instability that widely exists in non-singular bounce cosmologies in the framework of scalar-tensor and Horndeski/Galileon theories is removed by the effects of new operators introduced by the DHOST, due to the modification that they later bring about to the dispersion relation of perturbations. Hence, our results demonstrate that there is indeed a loophole for this type of bounce scenarios to be free from pathologies when primordial perturbations evolve through the bounce phase, and thus the theoretical {\it no-go} theorem for non-singular bounce cosmology of Horndeski/Galileon theories can be delicately evaded in DHOST extensions.
A. Ilyas, M. Zhu, Y. Zheng, et. al.
Thu, 20 Feb 20
23/61
Comments: 22 pages, 2 main figures, comments are welcome