We study the absorption and scattering of massless scalar waves propagating
in spherically symmetric spacetimes with dynamical cosmological constant both
in low-energy and high-energy zones. In the former low-energy regime, we solve
analytically the Regge-Wheeler wave equation and obtain an analytic absorption
probability expression which varies with MΛ​, where M is the
central mass and Λ is cosmological constant. The low-energy absorption
probability, which is in the range of [0,0.986701], increases monotonically
with increase in Λ. In the latter high-energy regime, the scalar
particles adopt their geometric optics limit value. The trajectory equation
with effective potential emerges and the analytic high-energy greybody factor,
which is relevant with the area of classically accessible regime, also
increases monotonically with increase in Λ, as long Λ is less
than or of the order of 104. In this high-energy case, the null cosmological
constant result reduces to the Schwarzschild value 27πrg2​/4.Comment: 12 pages, 6 figure