Unclear symbol use in step acceptance criteria:

[NAThompson]

In the docs for the adaptive steppers, the following statement relates the absolute and relative tolerances to the acceptance criteria via

For the Runge-Kutta controller the error made during one step is compared with eps_abs + eps_rel * ( ax * |x| + adxdt * dt * |dxdt| ).

What are the definitions of the symbols a_x and a_dxdt?

What norm is used to define |x| and |dxdt|?

[NAThompson]

My bad, sry.