  Majorana representation of quantum states by a constellation of n 'stars'
(points on the sphere) can be used to describe any pure state of a simple
system of dimension n+1 or a permutation symmetric pure state of a composite
system consisting of n qubits. We analyze the variance of the distribution of
the stars, which can serve as a measure of the degree of non-coherence for
simple systems, or an entanglement measure for composed systems. Dynamics of
the Majorana points induced by a unitary dynamics of the pure state is
investigated.
