Axion driven cosmic magneto-genesis during the QCD crossover

Abstract

We propose a mechanism for the generation of a magnetic field in the early universe during the QCD crossover assuming that dark matter is made of axions. Thermoelectric fields arise at pressure gradients in the primordial plasma due to the difference in charge, energy density and equation of state between the quark and lepton components. The axion field is coupled to the EM field, so when its spatial gradient is misaligned with the thermoelectric field, an electric current is driven. Due to the finite resistivity of the plasma an electric field appears that is generally rotational. For a QCD axion mass consistent with observational constraints and a conventional efficiency for turbulent dynamo amplification --- driven by the same pressure gradients responsible for the thermoelectric fields --- a magnetic field is generated on subhorizon scales. After significant Alfvénic unwinding it reaches a present day strength of $B\sim 10^{-13}$ G on a characteristic scale $L_B\sim$ 20 pc. The resulting combination of $B{L}_B^{1/2}$ is significantly stronger than in any astrophysical scenario, providing a clear test for the cosmological origin of the field through $\gamma$-ray observations of distant blazars. The amplitude of the pressure gradients may be inferred from the detection of concomitant gravitational waves, while several experiments are underway to confirm or rule out the existence of axions.

Published in PRL

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Cited by in corpus (14)

• Progress on Cosmological Magnetic Fields
• Sensitivity of the Cherenkov Telescope Array for probing cosmology and fundamental physics with gamma-ray propagation
• Can we observe the QCD phase transition-generated gravitational waves through pulsar timing arrays?
• Constraints on the intergalactic magnetic field using Fermi-LAT and H.E.S.S. blazar observations
• The scalar, vector, and tensor modes in gravitational wave turbulence simulations
• Axion detection through resonant photon-photon collisions
• Simulating relic gravitational waves from inflationary magnetogenesis
• Neutrino-electron magnetohydrodynamics in an expanding Universe
• Modified Friedmann equations via conformal Bohm -- De Broglie gravity
• Exploring scalar-photon interactions in energetic astrophysical events
• Suppression of pair beam instabilities in a laboratory analogue of blazar pair cascades
• Cosmological chirality and magnetic fields from parity violating particle decays
• Gravitational wave signal from primordial magnetic fields in the Pulsar Timing Array frequency band
• LISA and $\gamma$-ray telescopes as multi-messenger probes of a first-order cosmological phase transition