Spectral Lines from Relic Quantum Nonequilibrium

In the de Broglie-Bohm pilot-wave formulation of quantum theory, standard quantum probabilities arise spontaneously through a process of dynamical relaxation that is broadly similar to thermal relaxation in classical physics. If we are to regard this process as the cause of the quantum probabilities we observe today, then we must infer a primordial ‘quantum nonequilibrium’ in the remote past. Such quantum nonequilibrium may have left observable traces today, perhaps in the cosmic microwave background, or in relic particle species that decoupled in the very early universe and that have been sufficiently minimally interacting ever since. The search for the dark matter–that we observe today only through its gravitational interactions–has provided a compendium of particle species that could at least in
principle carry quantum nonequilibrium. If they did indeed exist, nonequilibrium distributions would not only demonstrate the need to reevaluate the canonical quantum formalism, but also generate new phenomena that lie outside the domain of conventional quantum theory, potentially opening up a large domain for investigation. We will develop a simple, parameter free, quantum field theoretical model of spectral measurement, and use it to demonstrate some of the novel effects that could occur to the profiles of the line spectra of such relic particles. We find for instance, line broadening effects that scale with the resolution of the telescope, the possibility of line narrowing and other effects that could cause multiple bumps to form. We use this discussion to comment on possible implications on the indirect search for dark matter.