  We present a novel approach for setting initial conditions on the mode
functions of the Mukhanov Sazaki equation. These conditions are motivated by
minimisation of the renormalised stress-energy tensor, and are valid for
setting a vacuum state even in a context where the spacetime is changing
rapidly. Moreover, these alternative conditions are potentially observationally
distinguishable. We apply this to the kinetically dominated universe, and
compare with the more traditional approach.
