@article{c5894717f04944edb2293d41a0e10b63,
title = "Time-domain properties of electromagnetic signals in a dynamical axion background",
abstract = "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.",
author = "Peter Adshead and Patrick Draper and Benjamin Lillard",
note = "Funding Information: We are grateful to Carlos Blanco, Nico Fernandez and Matt Reece for helpful conversations, and to Yoni Kahn for collaboration in the early stages of the work. The work of P. D. and B. L. is supported in part by the National Science Foundation Grant No. PHY-1719642, and the work of P. A., P. D. and B. L. is supported in part by the US Department of Energy Grant No. DE-SC0015655. P. A. acknowledges the hospitality of the Kavli Institute for Theoretical Physics, which is supported in part by the National Science Foundation under Grant No. NSF-PHY-1748958. B. L. thanks the Simons Center for Geometry and Physics, Stony Brook University at which some of the research for this paper was performed. Publisher Copyright: {\textcopyright} 2020 authors. Published by the American Physical Society.",
year = "2020",
month = dec,
day = "7",
doi = "10.1103/PhysRevD.102.123011",
language = "English (US)",
volume = "102",
journal = "Physical Review D",
issn = "2470-0010",
publisher = "American Physical Society",
number = "12",
}