  We consider the nonaxisymmetric linear theory of radially-stratified disks.
We work in a shearing-sheet-like approximation, where the vertical structure of
the disk is neglected, and develop equations for the evolution of a plane-wave
perturbation comoving with the shear flow (a shearing wave, or ``shwave''). We
calculate a complete solution set for compressive and incompressive
short-wavelength perturbations in both the stratified and unstratified
shearing-sheet models. We develop expressions for the late-time asymptotic
evolution of an individual shwave as well as for the expectation value of the
energy for an ensemble of shwaves that are initially distributed isotropically
in k-space. We find that: (i) incompressive, short-wavelength perturbations in
the unstratified shearing sheet exhibit transient growth and asymptotic decay,
but the energy of an ensemble of such shwaves is constant with time (consistent
with Afshordi, Mukhopadhyay & Narayan 2004); (ii) short-wavelength compressive
shwaves grow asymptotically in the unstratified shearing sheet, as does the
energy of an ensemble of such shwaves; (iii) incompressive shwaves in the
stratified shearing sheet have density and azimuthal velocity perturbations
\delta \Sigma,\delta v_y ~ t^{-Ri} (for |Ri| << 1), where Ri = N_x^2/(q
\Omega)^2 is the Richardson number, N_x^2 is the square of the radial
Brunt-Vaisala frequency and q\Omega is the effective shear rate; (iv) the
energy of an ensemble of incompressive shwaves in the stratified shearing sheet
behaves asymptotically as Ri t^{1-4Ri} for |Ri| << 1. For Keplerian disks with
modest radial gradients, |Ri| is expected to be << 1, and there will therefore
be weak growth in a single shwave for Ri < 0 and near-linear growth in the
energy of an ensemble of shwaves, independent of the sign of Ri.
