  We revisit the quantum phase transition from a paraelectric state to a
ferroelectric one and in particular the widespread distinction between a
longitudinal modes to transverse one. In contrast to transitions at finite
temperature, for a quantum phase transition breaking a discrete symmetry the
splitting between the modes is irrelevant. We show that an anisotropy in the
context of a quantum phase transition leads to a different behavior, compared
to a classical transition, and suggest an experiment to observe it. The result
is essential for explaining the pairing mechanism in strontium titanate.
