So as to anticipate a possible misunderstanding I remark that the
equations (93,
94,
95) with
from (89) and (91) are neither symmetric nor fully hyperbolic. Indeed the
underlying symmetry of the system (79,
80,
81), and (84) reveals itself only when the Lagrange multipliers
are used as variables. But (93,
94,
95,
89,
91) are equations for the physical variables
or in fact
, and
. Also the hyperbolicity in the whole state space is lost,
because the equations (89,
90) are restricted to linear terms. Therefore the system is
hyperbolic only in the neighbourhood of equilibrium. For a more
detailed discussion of these aspects, see Müller &
Ruggeri [39,
40].