Axion and dilaton + metric emerge from local and linear electrodynamics

Understand

We take a quick look at the different possible universally coupled scalar fields in nature.

• Then, we discuss how the gauging of the group of scale transformations (dilations), together with the Poincare group, leads to a Weyl-Cartan spacetime structure.
• There the dilaton field finds a natural surrounding.
• Moreover, we describe shortly the phenomenology of the hypothetical axion field.