Observational constraints on anisotropies for bouncing alternatives to inflation Agullo, Ivan Olmedo Nieto, Javier Antonio Wilson-Ewing, Edward We thank Jérome Quintin for helpful comments on an earlier version of this paper. I.A. is supported by the NSF grant PHY-2110273, and by the Hearne Institute for Theoretical Physics. J.O. is supported by the Spanish Government through the projects PID2020-118159GB-C43, PID2019- 105943GB-I00 (with FEDER contribution), and also by the \Operative Program FEDER2014-2020 Junta de Andalucía-Consejería de Economía y Conocimiento" under project E-FQM-262-UGR18 by Universidad de Granada. E.W.-E. is supported by the Natural Sciences and Engineering Research Council of Canada, and by the UNB Fritz Grein Research Award. We calculate how primordial anisotropies in the background space-time affect the evolution of cosmological perturbations for bouncing alternatives to inflation, like ekpyrosis and the matter bounce scenario. We find that the leading order effect of anisotropies in the contracting phase of the universe is to induce anisotropies in the cosmic microwave background with a very concrete form: a scale-invariant quadrupolar angular distribution. Sub-leading effects are the generation of higher-order moments in the angular distribution, as well as cross-correlations between scalar and tensor modes. We also find that observational constraints from the cosmic microwave background on the quadrupole moment provide strong bounds on allowed anisotropies for bouncing alternatives to inflation that are significantly more constraining than the bounds previously obtained using scaling arguments based on the conjectured Belinski-Khalatnikov-Lifshitz instability. 2022-11-28T11:57:20Z 2022-11-28T11:57:20Z 2022-08-23 journal article Published version: Ivan Agullo et al. Observational constraints on anisotropies for bouncing alternatives to inflation. JCAP10(2022)045 [DOI 10.1088/1475-7516/2022/10/045] https://hdl.handle.net/10481/78154 10.1088/1475-7516/2022/10/045 eng http://creativecommons.org/licenses/by-nc-nd/4.0/ open access Attribution-NonCommercial-NoDerivatives 4.0 Internacional