3.15 Consider the function f????,d(????) = |????| d2????, ???? d, where ???? is a real parameter. Then f????,d can be viewed as

3.15 Consider the function f????,d(????) = |????|

−d−2????, ???? ∈ ℝd, where ???? ∈ ℝ is a real parameter. Then f????,d can be viewed as the spectral density of an isotropic stochastic process on ℝd (ordinary intrinsic if ???? > 0, generalized stationary if ???? < 0 and generalized intrinsic if ???? = 0). In Section