  In this paper we describe physical properties arising in the vicinity of two
coupled quantum phase transitions. We consider a phenomenological model based
on two scalar order parameter fields locally coupled biquadratically and having
a common quantum critical point as a function of a quantum tuning parameter
such as pressure or magnetic field. A self-consistent treatment suggests that
the uniform static susceptibilities of the two order parameter fields may have
the same qualitative form at low temperature even where the forms differ
sharply in the absence of the biquadratic coupling. The possible limitations of
the self-consistent analysis leading to this prediction are considered.
