  The Fermi liquid-Wigner crystal transition in a two dimensional electronic
system is revisited with a focus on the nature of the fixed node approximation
done in quantum Monte Carlo calculations. Recently, we proposed (Phys. Rev.
Lett. 94, 046801 (2005)) that for intermediate densities, a hybrid phase (with
the symmetry of the crystal but otherwise liquid like properties) is more
stable than both the liquid and the crystal phase. Here we confirm this result
both in the thermodynamic and continuum limit. The liquid-hybrid transition
takes place at rs=31.5 +/- 0.5. We find that the stability of the hybrid phase
with respect to the crystal one is tightly linked to its delocalized nature. We
discuss the implications of our results for various transition scenarii
(quantum hexatic phase, supersolid, multiple exchange, microemulsions) proposed
in the literature.
