One-dimensional SU(4) spin-orbital model: A low-energy effective theory

The one-dimensional spin-orbital model is studied by means of Abelian boson ization. We derive the low-energy effective theory which enables us to stud y small deviations from the SU(4) symmetric point. We show that there exist s a massless region with algebraically decaying correlation functions simil ar to cos[(pi/2a(0))x]x(-3/2). When entering the massive phase, the system displays an approximate SO(6) enlarged symmetry with a dimerization type of ordering consisting in alternating spin and orbital singlets.