On Kottler's path: origin and evolution of the premetric program in gravity and in electrodynamics

Understand

In 1922, Kottler put forward the program to remove the gravitational potential, the metric of spacetime, from the fundamental equations in physics as far as possible.

• He successfully applied this idea to Newton's gravitostatics and to Maxwell's electrodynamics, where Kottler recast the field equations in premetric form and specified a metric-dependent constitutive law.
• We will discuss the basics of the premetric approach and some of its beautiful consequences, like the division of universal constants into two classes.
• We show that classical electrodynamics can be developed without a metric quite straightforwardly: the Maxwell equations, together with a local and linear response law for electromagnetic media, admit a consistent premetric formulation.