Blasts of Light from Axions

The nature of dark matter is one of the longest-standing puzzles in science. Axions or axionlike particles are a key possibility and arise in mechanisms to solve the strong CP problem, but also in low-energy limits of string theory. Extensive experimental and observational efforts are actively looking for "axionic" imprints. Independent of their nature, abundance, and contribution to the dark matter problem, axions form dense clouds around spinning black holes, grown by superradiant mechanisms. It was recently suggested that once couplings to photons are considered, an exponential (quantum) stimulated emission of photons ensues at large enough axion number. Here we solve numerically the classical problem in different setups. We show that laserlike emission from clouds exists at the classical level, and we provide the first quantitative description of the problem.