“…Quite differently from the case of a Schwarzschild background, the results for these test cases suggest an asymmetry between the cases µ = 0 and µ = 0. In the case of the wave equation, i.e., µ = 0, results point to the stability of the solutions [34,16,12,1,23,24], whereas for µ = 0, there are a number of results pointing in the direction of instability of the solutions under certain conditions [13,14,36,17,22,9,19].…”