Ruiz Cembranos, José AlbertoDelgado López, RafaelDobado González, Antonio2023-06-192023-06-192013-10-291550-799810.1103/PhysRevD.88.075021https://hdl.handle.net/20.500.14352/33420© 2013 American Physical Society. The authors thankfully acknowledge the computer resources, technical expertise, and assistance provided by the Barcelona Supercomputing Centre—Centro Nacional de Supercomputación—and the Tirant supercomputer support staff at Valencia. We are also pleased to thank Professor Antonio L. Maroto and Professor Torbjo¨rn Sjöstrand for their useful help and comments. This work has been supported by MICINN (Spain) Project Nos. FIS 2008-01323, FIS2011-23000, and FPA2011-27853-01 and Consolider-Ingenio MULTIDARK CSD2009-00064. R. L.D. is a fellow of FPI, Ref. BES-2012-056054.We explore the viscosities of a photon gas by means of the Euler-Heisenberg effective theory and quantum electrodynamics at zero electron chemical potential. We find parametric estimates that show a very large shear viscosity and an extremely small bulk viscosity (reflecting the very weak coupling simultaneously with a very approximate dilatation invariance). The system is of some interest because it exemplifies very neatly the influence of the breaking of scale invariance on the bulk viscosity.engjournal articlehttp://dx.doi.org/10.1103/PhysRevD.88.075021http://prd.aps.org/open access53Extra DimensionsCollider SignalsFluctuationsPhysicsFísica (Física)22 Física