  We investigate the nature of the interaction-driven Mott-Hubbard transition
of the half-filled $t_1{-}t_2$ Hubbard model in one dimension, using a
full-fledged variational Monte Carlo approach including a distance-dependent
Jastrow factor and backflow correlations. We present data for the evolution of
the magnetic properties across the Mott-Hubbard transition and on the
commensurate to incommensurate transition in the insulating state. Analyzing
renormalized excitation spectra, we find that the Fermi surface renormalizes to
perfect nesting right at the Mott-Hubbard transition in the insulating state,
with a first-order reorganization when crossing into the conducting state.
