  We revisit Stoner instability, an old problem but in a modern point of view.
An idea is to extract out dynamics of directional fluctuations of spins
explicitly, resorting to the CP$^{1}$ representation and integrating over their
amplitude fluctuations. As a result, we derive an effective field theory for
ferromagnetic quantum phase transitions in terms of bosonic spinons and
fermionic holons. We show that this effective field theory reproduces
overdamped spin dynamics in a paramagnetic Fermi liquid and magnon spectrum in
a ferromagnetic Fermi liquid. An interesting observation is that the velocity
of spinons becomes zero, approaching the ferromagnetic quantum critical point,
which implies emergence of local quantum criticality. Based on this scenario,
we predict the $\omega/T$ scaling behavior near ferromagnetic quantum
criticality beyond the conventional scenario of the weak-coupling approach.
