Axionic extension of the Einstein-aether theory: How does dynamic aether
  regulate the state of axionic dark matter?
  In the framework of axionic extension of the Einstein-aether theory we
establish the model, which describes a stiff regulation of the behavior of
axionic dark matter by the dynamic aether. The aether realizes this procedure
via the modified Higgs potential, designed for modeling of nonlinear
self-interaction of pseudoscalar (axion) field; the modification of this
potential is that its minima are not fixed, and their positions and depths
depend now on the square of the covariant derivative of the aether velocity
four-vector. Exact solutions to the master equations, modified correspondingly,
are obtained in the framework of homogeneous isotropic cosmological model. The
effective equation of state for axionic dark matter is of the stiff type.
Homogeneous perturbations of the pseudoscalar (axion) field, of the Hubble
function and of the scale factor are shown to fade out with cosmological time,
there are no growing modes, the model of stiff regulation is stable.
