RT Journal Article T1 Cosmological electromagnetic fields and dark energy A1 López Maroto, Antonio A1 Beltrán Jiménez, José AB We show that the presence of a temporal electromagnetic field on cosmological scales generates an effective cosmological constant which can account for the accelerated expansion of the universe. Primordial electromagnetic quantum fluctuations produced during electroweak scale inflation could naturally explain the presence of this field and also the measured value of the dark energy density. The behavior of the electromagnetic field on cosmological scales is found to differ from the well studied short-distance behavior and, in fact, the presence of a non-vanishing cosmological constant could be signalling the breakdown of gauge invariance on cosmological scales. The theory is compatible with all the local gravity tests, and is free from classical or quantum instabilities. Thus we see that, not only the true nature of dark energy can be established without resorting to new physics, but also the value of the cosmological constant finds a natural explanation in the context of standard inflationary cosmology. This mechanism could be discriminated from a true cosmological constant by upcoming observations of CMB anisotropies and large scale structure. PB Iop Publishing Ltd SN 1475-7516 YR 2009 FD 2009-03 LK https://hdl.handle.net/20.500.14352/44343 UL https://hdl.handle.net/20.500.14352/44343 LA eng NO © 2009 IOP Publishing Ltd and SISSA.We would like to thank J.D. Barrow, J.A.R. Cembranos and C. Tamarit for useful comments and suggestions. This work has been supported by DGICYT (Spain) project numbers FPA 2004 02602 and FPA 2005-02327, UCM-Santander PR34/07-15875, CAM/UCM 910309 and MEC grant BES-2006-12059. NO DGICYT (Spain) NO UCM-Santander NO CAM/UCM NO MEC DS Docta Complutense RD 6 abr 2025