  The ground state of chromonic liquid crystals, as revealed by a number of
recent experiments, is quite different from that of ordinary nematic liquid
crystals: it is twisted instead of uniform. The common explanation provided for
this state within the classical elastic theory of Frank demands that one
Ericksen's inequality is violated. Since in general such a violation makes
Frank's elastic free-energy functional unbounded below, the question arises as
to whether the twisted ground state can be locally stable. We answer this
question in the affirmative. In reaching this conclusion, a central role is
played by the specific boundary conditions imposed in the experiments on the
boundary of rigid containers and by a general formula that we derive here for
the second variation of Frank's elastic free energy.
