  T-Duality is a poorly understood symmetry of the space-time fields of string
theory that interchanges long and short distances. It is best understood in the
context of toroidal compactification where, loosely speaking, radii of the
torus are inverted. Even in this case, however, conventional techniques permit
an understanding of the transformations only in the case where the metric on
the torus is endowed with Abelian Killing symmetries. Attempting to apply these
techniques to a general metric appears to yield a non-local world-sheet theory
that would defy interpretation in terms of space-time fields. However, there is
now available a simple but powerful general approach to understanding the
symmetry transformations of string theory, which are generated by certain
similarity transformations of the stress-tensors of the associated conformal
field theories. We apply this method to the particular case of T-Duality and i)
rederive the known transformations, ii) prove that the problem of non-locality
is illusory, iii) give an explicit example of the transformation of a metric
that lacks Killing symmetries and iv) derive a simple transformation rule for
arbitrary string fields on tori.
