  Large (up to $\sim 100$ kt) liquid argon time-projection chamber detectors
are presently being considered for proton decay searches and neutrino
astrophysics, as well as for far detectors for the next generation of
long-baseline neutrino oscillation experiments that aim to determine neutrino
mass hierarchy and search for CP violation in the leptonic sector. These
detectors rely on the capabilities to assemble large volumes of LAr in
ultrahigh-purity conditions, possibly in an underground environment, and to
achieve relatively long drifts for the ionization charge. Several proposals
have been developed, each of which takes a different approach to the design of
the cryogenic vessels and has different scales of modularity to reach the final
mass dictated by physics. New detector concepts, with innovative designs of
readout electronics and novel methods for the readout of the ionization charge
and scintillation light, have been proposed.
