  We show strong numerical evidence in favor of an unexpected virtually gapless
spectrum, with edge states localized at the boundaries, in frustrated spin-1/2
antiferromagnetic ladders with an odd number of legs. These features can be
accurately reproduced by using a projected BCS wave function with a non-trivial
pairing, that mixes even and odd reflection symmetries. This approach gives the
correct classification of the excitations and provides a simple and very
appealing picture of an unconventional spin-liquid phase stabilized by
frustration.
