  Strong interaction among charge carriers can make them move like viscous
fluid. Here we explore alternating current (AC) effects in viscous electronics.
In the Ohmic case, incompressible current distribution in a sample adjusts fast
to a time-dependent voltage on the electrodes, while in the viscous case,
momentum diffusion makes for retardation and for the possibility of propagating
slow shear waves. We focus on specific geometries that showcase interesting
aspects of such waves: current parallel to a one-dimensional defect and current
applied across a long strip. We find that the phase velocity of the wave
propagating along the strip respectively increases/decreases with the frequency
for no-slip/no-stress boundary conditions. This is so because when the
frequency or strip width goes to zero (alternatively, viscosity go to
infinity), the wavelength of the current pattern tends to infinity in the
no-stress case and to a finite value in a general case. We also show that for
DC current across a strip with no-stress boundary, there only one pair of
vortices, while there is an infinite vortex chain for all other types of
boundary conditions.
