  We present a numerical investigation of the density fluctuations in a model
glass under cyclic shear deformation. At low amplitude of shear, below
yielding, the system reaches a steady absorbing state in which density
fluctuations are suppressed revealing a clear fingerprint of hyperuniformity up
to a finite length scale. The opposite scenario is observed above yielding,
where the density fluctuations are strongly enhanced. We demonstrate that the
transition to this state is accompanied by a spatial phase separation into two
distinct hyperuniform regions, as a consequence of shear band formation above
the yield amplitude.
