  The role of domain wall junctions in Carter's pentahedral model is
investigated both analytically and numerically. We perform, for the first time,
field theory simulations of such model with various initial conditions. We
confirm that there are very specific realizations of Carter's model
corresponding to square lattice configurations with X-type junctions which
could be stable. However, we show that more realistic realizations, consistent
with causality constraints, do lead to a scaling domain wall network with
Y-type junctions. We determine the network properties and discuss the
corresponding cosmological implications, in particular for dark energy.
