  Uniform-field effects for frustrated odd-leg integer-spin tubes (cylinder
type spin systems) are investigated in the weak interchain-coupling regime. We
predict that, as the field exceeds the spin gap, a two-component
Tomonaga-Luttinger liquid (TLL) appears due to the condensation of the doubly
degenerate lowest magnons. Furthermore, it is argued that when the uniform
field is so strong that the second lowest magnons are also condensed, the
two-component TLL is destroyed and a new one-component TLL emerges. This
quantum phase transition may be detected as a magnetization cusp.
