“…Moreover, it is quite reasonable to conjecture that the exponent p c (n, ℓ, µ, ν 2 ) is critical even for higher dimensions. Indeed, for µ = ν 2 = 0 we have that p c (n, ℓ, 0, 0) = p Str (n, ℓ) for n 2 and p c (n, ℓ, 0, 0) = p Fuj (ℓ) for n = 1 (see [18,Remark 1.6] for the one-dimensional case) according to the results for (2) with power nonlinearity that we recalled in the introduction. In particular, when ℓ = 0 too we find that p c (n, 0, 0, 0) is the solution to the quadratic equation (n − 1)p 2 − (n + 1)p − 2 = 0, namely, the celebrated exponent named after the author of [31] which is the critical exponent for the semilinear wave equation.…”