  Under the application of a force, a material will deform and, hence, the
crystal lattice will experience strain. This induced strain will alter the
electronic properties of the material. In particular, strain in graphene
generates an artificial vector potential which, if spatially varying, admits a
pseudo-magnetic field. Current theories for spatially varying strain use linear
or finite strain theory whose derivation is based on small displacements of
infinitesimal length vectors. Here we apply a differential geometry method to
derive a strain theory for large displacements of finite length vectors. This
method gives a finite displacement term whose contribution is comparable to
that of the linear strain term. Further to this, we show that a 'domain
wall'-like pseudo-magnetic field profile can be generated when a wide graphene
ribbon is subjected to a pair of opposing point forces (point stretch). The
resulting field is a function of the new finite displacement term only and
displays a maximum strength of over three times that which is predicted by the
linear strain theory. These results extend the current theories of strain,
which are based on the transformation of infinitesimal length vectors, to
finite length vectors, thus providing an accurate description of
pseudo-magnetic field structures in strained materials.
