RT Journal Article T1 Eternal versus singular observers in interacting dark-energy-dark-matter models A1 Álvarez Ortega, Diego A1 Olmo, Gonzalo J. A1 Rubiera García, Diego A1 Sáez Chillón Gómez, Diego AB Interacting dark-energy-dark-matter models have been widely analyzed in the literature in an attempt to find traces of new physics beyond the usual cosmological (Lambda CDM) models. Such a coupling between both dark components is usually introduced in a phenomenological way through a flux in the continuity equation. However, models with a Lagrangian formulation are also possible. A class of the latter assumes a conformal/disformal coupling that leads to a fifth force on the dark-matter component, which consequently does not follow the same geodesics as the other (baryonic, radiation, and dark-energy) matter sources. Here we analyze how the usual cosmological singularities of the standard matter frame are seen from the dark-matter one, concluding that by choosing an appropriate coupling, dark-matter observers will see no singularities but a non beginning, non ending universe. By considering two simple phenomenological models we show that such a type of coupling can fit observational data as well as the usual Lambda CDM model. PB Amer Physical Soc SN 2470-0010 YR 2022 FD 2022-07-26 LK https://hdl.handle.net/20.500.14352/71969 UL https://hdl.handle.net/20.500.14352/71969 LA eng NO © 2022 Amer Physical Soc.D. A. O. is funded by the JAE program of CSIC (Spain). D. R. G. is funded by the Atraccion de Talento Investigador program of the Comunidad deMadrid (Spain) No. 2018-T1/TIC-10431. D. S.-C. G. is funded by the University of Valladolid (Spain), Ref. POSTDOC UVA20. This work is supported by the SpanishGrantsNo. FIS2017-84440-C2-1-P, No. PID2019-108485 GB-I00, No. PID2020-116567 GBC21, and No. PID2020-117301GA-I00 funded by MCIN/AEI/10.13039/501100011033 ("ERDF A way of making Europe" and "PGC Generacion de Conocimiento"), the project PROMETEO/2020/079 (Generalitat Valenciana), the project H2020-MSCA-RISE-2017 Grant No. FunFiCO777740, the Project No. i-COOPB20462 (CSIC), the FCT Projects No. PTDC/FIS-PAR/31938/2017 and No. PTDC/FIS-OUT/29048/2017, and the Edital 006/2018 PRONEX (FAPESQ-PB/CNPQ, Brazil, Grant No. 0015/2019). This article is based upon work from COST Action CA18108, supported by COST (European Cooperation in Science and Technology). We are thankful for the anonymous referee's comments that allowed us to improve the manuscript as compared to its first version. NO Unión Europea. Horizonte 2020 NO Ministerio de Economía y Competitividad (MINECO)/FEDER NO Ministerio de Ciencia e Innovación (MICINN)/AEI NO Comunidad de Madrid NO Generalitat Valenciana NO Universidad de Valladolid NO Consejo Superior de Investigaciones Científicas (CSIC) NO Fundação para a Ciência e a Tecnologia (FCT) NO FAPESQ-PB/CNPQ, Brazil DS Docta Complutense RD 12 may 2025