Time-domain properties of electromagnetic signals in a dynamical axion background

Peter Adshead, Patrick Draper, Benjamin Lillard

Research output: Contribution to journalArticlepeer-review


Electromagnetic waves in a dynamical axion background exhibit superluminal group velocities at high frequencies and instabilities at low frequencies, altering how photons propagate through space. Local disturbances propagate causally, but unlike in ordinary Maxwell theory, propagation occurs inside as well as on the light cone. For the unstable modes, the energy density in the electromagnetic field grows exponentially along timelike displacements. In this paper we derive retarded Green functions in axion electrodynamics in various limits and study the time-domain properties of propagating signals.

Original languageEnglish (US)
Article number123011
JournalPhysical Review D
Issue number12
StatePublished - Dec 7 2020

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)


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