The ground-state properties and thermodynamics of the one-dimensional SU(4)
symmetric spin system with orbital degeneracy are investigated using the q
uantum Monte Carlo loop algorithm. The spin spin correlation functions exhi
bit a 4-site periodicity, and their low-temperature behavior is controlled
by two correlation lengths that diverge like the inverse temperature, while
the entropy is linear in temperature and its slope is consistent with thre
e gapless modes of velocity pi/2. The physical implications of these result
s are discussed.