We investigate the properties of single-walled armchair carbon nanotubes in
presence of transverse electric and magnetic fields. We find via band structure
calculations that these fields can break particle-hole symmetry as well as that of the two Dirac points. Additionally, the speed of the left and right movers
is generally different in the presence of both electric and magnetic fields. We consider the effect of these fields on Coulomb interactions within the tube and
show that they can be used to tune the interaction parameter K associated with the Luttinger liquid properties of the tube. Finally, we discuss finite size
effects and Coulomb blockade physics in this context.