The fine-structure constant combines an extraordinary number of physical properties of our universe: the speed of light, the charge of an electron, energy differences in quantum mechanics, and more.
According to the theory of the renormalization group, the value of the fine-structure constant (the strength of the electromagnetic interaction) grows logarithmically as the energy scale is increased.
There is no known way to solve the horizon problem with variation of the fine-structure constant, because its variation does not change the causal structure of spacetime.
The coupling constant sets the magnitude of the force of interaction; for example, in quantum electrodynamics, the fine-structure constant is a coupling constant.
