  String-localized quantum field theory allows renormalizable couplings
involving massive vector bosons, without invoking negative-norm states and
compensating ghosts. We analyze the most general coupling of a massive vector
boson to a scalar field, and find that the scalar field necessarily comes with
a quartic potential which has the precise shape of the shifted Higgs potential.
In other words: the shape of the Higgs potential has not to be assumed, but
arises as a consistency condition among fundamental principles of QFT: Hilbert
space, causality, and covariance. The consistency can be achieved by relaxing
the localization properties of auxiliary quantities, including interacting
charged fields, while observable fields and the S-matrix are not affected. This
is an instance of the "L-V formalism" - a novel model-independent scheme that
can be used as a tool to "renormalize the non-renormalizable" by adding a total
derivative to the interaction.
