While considerable efforts in the form of numerical atomistic simulations have been expended to understand the mechanics of defect formation under applied strain, analogous analytical efforts have been rather few. In this work, based on the physics at the nanoscale, defect nucleation in single-walled carbon nanotubes is studied using both classical continuum field theory as well as gauge field theory of defects. Despite the inherent continuum assumption in our models, reasonably close qualitative and quantitative agreement with existing atomistic simulations is obtained. The latter lends credence to the belief that continuum formulations, with correct incorporation of the relevant physics, can be a powerful and yet simple tool for exploring nanoscale phenomena in carbon nanotubes. The results are more sensitive to chirality than to the size of the nanotubes. © 2005 American Institute of Physics.