The Hankel Transform of the Sum of Consecutive Generalized ...

The Hankel Transform of the Sum of Consecutive Generalized ... The Hankel Transform of the Sum of Consecutive Generalized ...

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13.07.2015 Views

10The characteristic equationhas the solutions4z 2 − 4 c z + 1 = 0z 1,2 = 1 2and the integral solution of (23) isλ n = E 1 z n 1 + E 2 z n 2(c ± √ )c 2 − 1 .(n ∈ N).We evaluate values E 1 and E 2 from the initial conditions (λ −1 = 0; λ 0 = 1).i.e,In other to solve our problem, we will choose c = − L+22 √ L . HenceFinally, we obtain:z k = −t k4 √ L (k = 1, 2), where t 1,2 = L + 2 ± √ L 2 + 4.λ n =(−1) n2 · 4 n L n 2√L2 + 4λ n =After replacing in (22), we obtain:( )t n+11 − t n+12(λ = −1, 0, 1, . . .),(−1)n2 · 4 n L n 2 ξ ψ n+1 (λ = −1, 0, 1, . . .).ˆα n = − L + 22 √ L + 14 √ L · ψn+2ψ n+1+ √ L · ψn+1ψ n+2, (32)ˆβ n = ψ nψ n+2. (33)4ψn+12If a new weight function ˜w(x) is introduced bythen we have˜w(x) = ŵ(ax + b)˜α n = ˆα n − b, ˜βn = ˆβ n(n ≥ 0).aa 2Now, by using x ↦→ x−L−12 √ , i.e., a = 1L 2 √ L+1and b = −L 2 √ , we have the weight functionLThusand˜w(x) = ŵ( x − L − 12 √ L ) = 1 ( x − L − 12 2 √ L+ L + 2 ) √2 √ 1 −L( x − L − 1) 2.2 √ L˜α n = −1 + 1 2 · ψn+2ψ n+1+ 2L · ψn+1ψ n+2(n ∈ N 0 ), (34)

11Example 4.2. For L = 4 we getwherefrom˜β 0 = (L + 2) π 2 , ˜βn = L ψ nψ n+2ψ 2 n+1P 0 (x) = 1, ‖P 0 ‖ 2 = 3π,P 1 (x) = x − 173 , ‖P 1‖ 2 = 32π3 ,P 2 (x) = x 2 − 434 x + 1014 , ‖P 2‖ 2 = 42π,(n ∈ N). (35)P 3 (x) = x 3 − 33121 x2 + 157921 x − 218921 , ‖P 3‖ 2 = 3520π21 ,˜α 0 = 17 3 , ˜β0 = 3π, ˜α 1 = 6112 , ˜β1 = 32 9 , ˜α 2 = 42184 , ˜β2 = 6316 .Introducing the weight˘w(x) = 2L π ˜w(x)will not change the monic polynomials and their recurrence relations, only it willmultiply the norms by the factor 2L/π, i.e.˘P k (x) ≡ P k (x), ‖ ˘P k ‖ 2˘w =∫ ba˘P k (x) ˘w(x) dx = 2L π ‖P k‖ 2 (k ∈ N 0 ),˘β 0 = L(L + 2), ˘βk = ˜β k (k ∈ N), ᾰ k = ˜α k (k ∈ N 0 ).Here is˘β 0 ˘β1 · · · ˘β n−1 = Ln2 · ψn+1ψ n. (36)In the book [?], W. Gautschi has treated the next problem: If we know all aboutthe MOPS orthogonal with respect to ˘w(x) what can we say about the sequence{Q n (x)} orthogonal with respect to a weightw d (x) = ˘w(x) (d /∈ support( ˜w)) ?x − dW. Gautshi has proved that, by the auxiliary sequence∫r −1 = − w d (x) dx, r n = d − ᾰ n − ˘β n(n = 0, 1, . . .),r n−1Rit can be determinedα d,0 = ᾰ 0 + r 0 , α d,k = ᾰ k + r k − r k−1 ,β d,0 = −r −1 , β d,k = ˘β k−1r k−1r k−2(k ∈ N).

11Example 4.2. For L = 4 we getwherefrom˜β 0 = (L + 2) π 2 , ˜βn = L ψ nψ n+2ψ 2 n+1P 0 (x) = 1, ‖P 0 ‖ 2 = 3π,P 1 (x) = x − 173 , ‖P 1‖ 2 = 32π3 ,P 2 (x) = x 2 − 434 x + 1014 , ‖P 2‖ 2 = 42π,(n ∈ N). (35)P 3 (x) = x 3 − 33121 x2 + 157921 x − 218921 , ‖P 3‖ 2 = 3520π21 ,˜α 0 = 17 3 , ˜β0 = 3π, ˜α 1 = 6112 , ˜β1 = 32 9 , ˜α 2 = 42184 , ˜β2 = 6316 .Introducing <strong>the</strong> weight˘w(x) = 2L π ˜w(x)will not change <strong>the</strong> monic polynomials and <strong>the</strong>ir recurrence relations, only it willmultiply <strong>the</strong> norms by <strong>the</strong> factor 2L/π, i.e.˘P k (x) ≡ P k (x), ‖ ˘P k ‖ 2˘w =∫ ba˘P k (x) ˘w(x) dx = 2L π ‖P k‖ 2 (k ∈ N 0 ),˘β 0 = L(L + 2), ˘βk = ˜β k (k ∈ N), ᾰ k = ˜α k (k ∈ N 0 ).Here is˘β 0 ˘β1 · · · ˘β n−1 = Ln2 · ψn+1ψ n. (36)In <strong>the</strong> book [?], W. Gautschi has treated <strong>the</strong> next problem: If we know all about<strong>the</strong> MOPS orthogonal with respect to ˘w(x) what can we say about <strong>the</strong> sequence{Q n (x)} orthogonal with respect to a weightw d (x) = ˘w(x) (d /∈ support( ˜w)) ?x − dW. Gautshi has proved that, by <strong>the</strong> auxiliary sequence∫r −1 = − w d (x) dx, r n = d − ᾰ n − ˘β n(n = 0, 1, . . .),r n−1Rit can be determinedα d,0 = ᾰ 0 + r 0 , α d,k = ᾰ k + r k − r k−1 ,β d,0 = −r −1 , β d,k = ˘β k−1r k−1r k−2(k ∈ N).

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