Bouncing alternatives to inflation

Although the inflationary paradigm is the most widely accepted explanation for the current cosmological observations, it does not necessarily correspond to what actually happened in the early stages of our Universe. To decide on this issue, two paths can be followed: first, all the possible predictions it makes must be derived thoroughly and compared with available data, and second, all the imaginable alternatives must be ruled out. Leaving the first task to all other contributors of this volume, we concentrate here on the second option, focusing on the bouncing alternatives and their consequences. Among the bouncing alternatives we have: the exotic hydrodynamical fluids that violate the null-energy condition, the minimally coupled scalar fields theories, and the conformal galileons