  In a recent paper, W. She, J. Yu and R. Feng reported the slight deformations
observed upon transmission of a light pulse through a short length of a silica
glass nano-filament. Relating the shape and magnitude of these deformations to
the momentum of the light pulse inside and outside the filament, these authors
concluded that, within the fiber, the photons carry the Abraham momentum. We
present an alternative evaluation of force and momentum in a system similar to
the experimental setup of She et al. Using precise numerical calculations that
take into account not only the electromagnetic momentum inside and outside the
filament, but also the Lorentz force exerted by a light pulse in its entire
path through the nano-waveguide, we conclude that the net effect should be a
pull (rather than a push) force on the end face of the nano-filament.
