  We show that strong Luttinger correlations of the electron liquid in armchair
carbon nanotubes lead to a significant enhancement of the onset temperature of
the putative twist Peierls instability. The instability results in a
spontaneous uniform twist deformation of the lattice at low temperatures, and a
gapped ground state. Depending on values of the coupling constants the umklapp
electron scattering processes can assist or compete with the twist instability.
In case of the competition the umklapp processes win in wide tubes. In narrow
tubes the outcome of the competition depends on the relative strength of the
e-e and e-ph backscattering. Our estimates show that the twist instability may
be realized in free standing (5,5) tubes.
