RT Journal Article T1 Dark energy: the absolute electric potential of the universe A1 López Maroto, Antonio A1 Beltrán Jiménez, José AB Is there an absolute cosmic electric potential? The recent discovery of the accelerated expansion of the universe could be indicating that this is certainly the case. In this essay we show that the consistency of the covariant and gauge-invariant theory of electromagnetism is truly questionable when considered on cosmological scales. Out of the four components of the electromagnetic field, Maxwell's theory contains only two physical degrees of freedom. However, in the presence of gravity, one of the "unphysical" states cannot be consistently eliminated, thus becoming real. This third polarization state is completely decoupled from charged matter, but can be excited gravitationally, thus breaking gauge invariance. On large scales the new state can be seen as a homogeneous cosmic electric potential, whose energy density behaves as a cosmological constant. PB World Scientific Publ Co Pte Ltd SN 0218-2718 YR 2009 FD 2009-12-31 LK https://hdl.handle.net/20.500.14352/44299 UL https://hdl.handle.net/20.500.14352/44299 LA eng NO © World Scientific Publ Co Pte Ltd. This work has been supported by the Ministerio de Ciencia e Innovación (Spain) projects FIS 2008-01323 and FPA 2008 00592, UCM-Santander PR34/07-15875, CAM/UCM 910309 and MEC grant BES-2006-12059. NO Ministerio de Ciencia e Innovación (Spain) NO UCM-Santander NO CAM/UCM NO MEC DS Docta Complutense RD 6 abr 2025