  Angle resolved photoemission experiments by Kanigel, et al (cond-mat/0605499)
[Nature Physics 2, 447 (2006)] have made a remarkable observation that low
energy electronic excitations in the normal state of underdoped cuprate
superconductors exist on open ``Fermi arcs'' instead of a closed Fermi surface.
These arcs shrink upon cooling, with the arc length appearing to extrapolate to
nodal points at zero temperature. We show that this striking non-Fermi liquid
behavior could result from the underdoped normal state above Tc lying in the
vicinity of a quantum phase transition between a d-wave superconductor and a
correlated insulating phase.
