  We investigate the consistency conditions for matter fields coupled to the
four-dimensional (${\cal N} = 1$ supersymmetric) $\mathbb{CP}(1)$ nonlinear
sigma model (the coset space $SU(2)_G/U(1)_H$). We find that consistency
requires that the $U(1)_H$ charge of the matter be quantized, in units of half
of the $U(1)_H$ charge of the Nambu-Goldstone (NG) boson, if the matter has a
nonsingular kinetic term and the dynamics respect the full group $SU(2)_G$. We
can then take the linearly realized group $U(1)_H$ to comprise the weak
hypercharge group $U(1)_Y$ of the Standard Model. Thus we have charge
quantization without a Grand Unified Theory (GUT), completely avoiding problems
like proton decay, doublet-triplet splitting, and magnetic monopoles. We
briefly investigate the phenomenological implications of this model-building
framework. The NG boson is fractionally charged and completely stable. It can
be naturally light, avoiding constraints while being a component of dark matter
or having applications in nuclear physics. We also comment on the extension to
other NLSMs on coset spaces, which will be explored more fully in a followup
paper.
