The axion is an hypothetical particle, which has never been detected. It was born as an elegant solution to the problem of CP in strong interactions and is one of the candidates for dark matter.
It deals with the PHYSICal properties of the universe.
particle physics is the branch of physics that studies the elementary constituents of matter and radiation
Conduction
They're not. Fundamental particles (mostly subatomic) are the carriers of the fundamental forces. Most of these particles are bosons.
A neutron