Oscillon of Ultra-Light Axion-like Particle

Understand

Ultra-light axion-like particle (ULAP) is one of attractive candidates for cold dark matter.

• Because the de Broglie wavelength of ULAP with mass $\sim 10^{-22} {\rm eV}$ is $\mathcal{O}({\rm kpc})$, the suppression of the small scale structure by the uncertainty principle can solve the core-cusp problem.
• Frequently, ULAP is assumed to be uniformly distributed in the present universe.
• In typical ULAP potentials, however, strong self-resonance at the beginning of oscillation invokes the large fluctuations, which may cause the formation of the dense localized object, oscillon.