  Based on recently proposed U(1)xSU(2) Chern-Simons gauge field theory, an
interpretation of the transport and magnetic relaxation properties of
underdoped cuprates is proposed, taking into account the short range
antiferromagnetic order. The interplay of the doping-dependent spin gap
(explicitly derived by us) effect and dissipation due to gauge fluctuations
gives rise to a crossover from metallic to insulating behavior of conductivity
as temperature decreases, in semi-quantitative agreement with experimental
data. For the same reason the magnetic relaxation rate shows a maximum nearby.
Various crossover temperatures related to spin gap effects are shown to be
different manifestations of the same energy scale.
