  Parametrically excited standing waves are observed on a cylindrical fluid
filament. These are the cylindrical analog of Faraday instability in a flat
surface or spherical droplet. Using the Floquet technique, linear stability
analysis has been investigated on a viscous cylindrical fluid surface, which is
subjected to a time-periodic radial acceleration. Viscosity has a significant
impact on the critical forcing amplitude as well as the dispersion relation of
the non-axis symmetric patterns. The effect of viscosity on onset parameters of
the pattern with azimuthal wavenumber, $m=1$, has shown different dependency
from $m>1$. The effect of viscosity increases with an increasing $m$ is also
observed.
