Large-Scale Magnetic Fields, Dark Energy and QCD

Understand

Cosmological magnetic fields are being observed with ever increasing correlation lengths, possibly reaching the size of superclusters, therefore disfavouring the conventional picture of generation through primordial seeds later amplified by galaxy-bound dynamo mechanisms.

• In this paper we put forward a fundamentally different approach that links such large-scale magnetic fields to the cosmological vacuum energy.
• In our scenario the dark energy is due to the Veneziano ghost (which solves the $U(1)_A$ problem in QCD).
• The Veneziano ghost couples through the triangle anomaly to the electromagnetic field with a constant which is unambiguously fixed in the standard model.