http://arxiv.org/abs/1801.04676
In recent years there are lots of interests to discuss frame dependences/independences of the cosmological perturbations under the conformal transformations. This problem was investigated in terms of the covariant approach for a single component universe, and it was found that the covariant approach is very powerful to pick out the perturbative variables which are both gauge and conformal invariant. In this work, we extend the covariant approach to the universe with multicomponent fluids. We find that similar results can be derived as expected. In addition, some other interesting perturbations are also identified to be conformal invariant, such as entropy perturbation between two different components.
Y. Zheng, Y. Mou, H. Rao, et. al.
Tue, 16 Jan 18
50/79
Comments: 10 pages, to be published in Chinese Physics C