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Applied Modeling Techniques and Data Analysis 2


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: 1 ≤ inh + 1 } of non-negative integers such that

image

      For the sake of simplicity, we have omitted the last three arguments of the function uBS and all arguments of the functions image and image.

      To define image, consider the differential operator

image

      where

      and

image

      are the terms of the Taylor expansions of the functions aij(z) and ai(z) around the point image.

      Following Pagliarani and Pascucci (2017), define the vector image by

image

      the matrix image by

image

      and the operator image by

      [2.8]image

image

      and the operator image as the differential operator acting on the z-variable and defined by (Pagliarani and Pascucci 2017, Equation D.2) as

image

      [2.9]image

      Here, we wrote all the arguments of the function imageto show that it

      does not depend on y and z.

      Note that a11(z) = -a1(z). It follows that

image

      and equation [2.9] can be written as

image

      where the operator image is given by (Lorig et al. 2017, Equation 3.14) as

      It is well-known that

image

      The first term on the right-hand side of equation [2.6] takes the form of (Lorig et al. 2017, Equation 3.13)

image image

      (see Lorig et al. (2017), Equation 3.15). This is because the function image does not depend on y and z.

      From Lorig et al. (2017), Lemma 3.4, we have

      where

image

      and where

image

      is the mth Hermite polynomial.

      We must still calculate the expression in the third line of equation [2.6] for h ≥ 2 (it is equal to 1 when h = 1). From Lorig et al. (2017), Proposition 3.5, we have

      [2.12]image

      where the coefficients ch,h−2q are defined recursively by

image image

      and

image

      where the dots denote the terms containing image and image∙ The functions image take the form

image