Dobado González, AntonioLlanes Estrada, Felipe JoséRodríguez Fernández, David2023-06-172023-06-172016-07-300217-751X10.1142/S0217751X16501189https://hdl.handle.net/20.500.14352/18993© World scientific publ co pte LTD. We thank Antonio Maroto for a critical reading of the cosmology aspects of the work. Supported by the Spanish Excellence Network on Hadronic Physics FIS2014-57026-REDT, and by grants UCM:910309, MINECO:FPA2011-27853-C02-01, MINECO:FPA2014- 53375-C2-1-P and CPAN Consolider-Ingenio 2010. DRF was partially supported by a GRUPIN 14-108 research grant from Principado de Asturias.We point out that in the early universe, for temperatures in the approximate interval 150-80 MeV (after the quark-gluon plasma), pions carried a large share of the entropy and supported the largest inhomogeneities. Its thermal conductivity (previously calculated) allows the characterization of entropy production due to equilibration (damping) of thermal fluctuations. Simple model distributions of thermal fluctuations are considered and the associated entropy production evaluated.engjournal articlehttp://dx.doi.org/10.1142/S0217751X16501189http://www.worldscientific.com/https://arxiv.org/abs/1507.06386open access53Entropy productionPion gasParticle cosmologyHadron and lepton eraFísica (Física)22 Física