  The interplay between quarter-filled and half-filled umklapp scattering has
been examined by applying the renormalization group method to a one-dimensional
quarter-filled electron system with dimerization, on-site (U) and
nearest-neighbor (V) repulsive interactions. The phase diagram on the U-V plane
is obtained at absolute zero temperature where the Mott insulator (the charge
ordered insulator) is found for smaller (larger) V. By choosing the moderate
parameter in the region of Mott insulator, it is shown that the resistivity
exhibits a crossover from behavior of quarter-filling to that of half-filling
with decreasing temperature.
