  We calculate the change in the correlation gap of armchair carbon nanotubes
with uniaxial elastic strain. We predict that such a stretching will enlarge
the correlation gap for all carbon nanotubes by a change that could be as large
as several meV per percent of applied strain, in contrast with pure band
structure calculations where no change for armchair carbon nanotubes is
predicted. The correlation effects are considered within a self-consistent
Hartree-Fock approximation to the Hubbard model with on-site repulsion only.
