  Conditions for existence, uniqueness and stability of bunch steady states are
considered. For the existence uniqueness problem, simple algebraic equations
are derived, showing the result both for the action and Hamiltonian domain
distributions. For the stability problem, van Kampen theory is used. Emerging
of discrete van Kampen modes show either loss of Landau damping, or
instability. This method can be applied for an arbitrary impedance, RF shape
and beam distribution function Available areas on intensity-emittance plane are
shown for resistive wall wake and single harmonic, bunch shortening and bunch
lengthening RF configurations.
