  Subcritical transition to turbulence in spatially developing boundary layer
flows can be triggered efficiently by finite amplitude perturbations. In this
work, we employ adjoint-based optimization to identify optimal initial
perturbations in the Blasius boundary layer, culminating in the computation of
the subcritical transition critical energy threshold and the associated fully
localized critical optimum in a spatially extended configuration, the so called
minimal seed. By dynamically rescaling the variables with the local boundary
layer thickness, we show that the identified edge trajectory approaches the
same attracting phase space region as previously reported edge trajectories,
and reaches the region more efficiently.
