Ponderomotive Effects of Ultralight Dark Matter

TL;DR

This paper introduces a new class of second-order quadratic effects caused by ultralight dark matter, which influence Standard Model particles and could be detectable through precision experiments.

Contribution

It demonstrates how ultralight dark matter can produce ponderomotive-like effects on particles, expanding the understanding of dark matter interactions beyond first-order effects.

Findings

Second-order effects scale with the square of dark matter field amplitude.

Calculated observables in electron g-2 experiments match previous field theory results.

Current electron g-2 experiments do not surpass astrophysical bounds, but other experiments might.

Abstract

I exhibit a new class of quadratic effects of ultralight dark matter. Axions, dark photons, and dilatons can exert rapidly oscillating forces, torques, and mass shifts on Standard Model particles. These effects average to zero at first order, but shift particle properties at second order, in analogy to the ponderomotive force in optics. Remarkably, these effects scale with the square of the amplitude of the dark matter field, even when the field's direct physical effects depend only on its derivatives. I calculate the resulting observables in electron $g_e - 2$ experiments using classical mechanics, recovering results previously derived using field theory. When considered properly, these particular experiments do not beat astrophysical bounds, but other precision experiments may have interesting sensitivity.