Proceedings of the 2nd IFAC Workshop on Fractional Differentiation and its Applications Porto, Portugal, July 19-21, 2006
N-FRACTIONAL CALCULUS OF SOME PRODUCTS OF SOME FUNCTION Katsuyuki Nishimoto ∗ ∗
Institute for Applied Mathematics, Descartes Press Co. 2- 13- 10 Kaguike, Koriyama, 963 - 8833, JAPAN Fax : + 81 - 24 - 922 - 7596
Abstract: In this article, N- fractional calculus of products of power functions (z − c)α and (z − c)β , (z − c = 0) and that of products of logarithmic functions (log(z − c))−α , and (log(z − c))−β , (z − c = 0, 1) are discussed . Keywords: Fractional Calculus, N- Fractional Calculus Operator, N-Fractional Calculus of Products
O ≤ arg(ζ − z) ≤ 2π f or C+ ,
1. INTRODUCTION ( DEFINITION OF FRACTIONAL CALCULUS )
ζ = z, z ∈ C, ν ∈ R,
(I) Definition. (Nishimoto, 1984)
Γ; Gamma f unction,
Let D = {D− , D+ } , C = {C− , C+ }, where C− be a curve along the cut joining two points z and −∞+iIm(z), C+ be a curve along the cut joining two points z and ∞ + iIm(z), D− be a domain surrounded by C− , D+ be a domain surrounded by C+ ( Here D contains the points over the curve C ). Moreover, let f = f (z) be a regular function in D(z ∈ D) , fν = (f )ν = C (f )ν Γ(ν + 1) f (ζ)dζ = 2πi (ζ − z)ν+1
then (f )ν is the fractional differintegration of arbitrary order ν ( derivatives of order ν for ν > 0, and integrals of order −ν for ν < 0 ), with respect to z , of the function f , if |(f )ν | < ∞. (II) On the fractional calculus operator N ν (Nishimoto, 1991) Theorem A. Let fractional calculus operator ( Nishimoto’s Operator ) N ν be Nν = (
(ν ∈ / Z − ), (1)
ν→−m
(2)
C
dζ ) (ζ − z)ν+1
with N −m = lim N ν ν→−m
where −π ≤ arg(ζ − z) ≤ π f or C− ,
(ν ∈ / Z − ), (3)
(Ref er to (N ishimoto, 1984))
C
(f )−m = lim (f )ν (m ∈ Z + ),
Γ(ν + 1) 2πi
(m ∈ Z + ),
and define the binary operation ◦ as
(4)
N β ◦ N α f = N β N α f = N β (N α f )
(5)
(α, β ∈ R),
2. N- FRACTIONAL CALCULUS OF PRODUCTS OF SOME POWER FUNCTIONS In the following α, β, γ ∈ R , for our convenience.
then the set {N ν } = {N ν |ν ∈ R}
(6)
is an Abelian product group ( having continuous index ν ) which has the inverse transform operator (N ν )−1 = N −ν to the fractional calculus operator N ν , for the function f such that f ∈ F = {f ; 0 = |fν | < ∞, ν ∈ R}, where f = f (z) and z ∈ C. ( vis. −∞ < ν < ∞ ). β
Theorem 1. Let P = P (α, β, γ) :=
sinπα · sinπ(γ − α − β) (1) sinπ(α + β) · sinπ(γ − α)
(|P (α, β, γ)| = M < ∞) and Q = Q(α, β, γ) := P (β, α, γ)
( For our convenience, we call N ◦ N as product of N β and N α ) ν
Theorem B. ” F.O.G. {N }) ” is an ” Action product group which has continuous index ν ” for the set of F . ( F.O.G. ; Fractional calculus operator group )
(|P (β, α, γ)| = M < ∞) When α, β, γ ∈ / Z0+ , we have ; (i) ((z − c)α · (z − c)β )γ = e−iπγ P (α, β, γ)
Γ(γ − α − β) Γ(−α − β)
×(z − c)α+β−γ .
(3)
Theorem C. Let
(Re(α + β + 1) > 0, (1 + α − γ) ∈ / Z0− ),
S := {± N ν } ∪ {0} = {N ν } ∪ {− N ν } ∪ {0} . (7) (ν ∈ R) Then the set S is a commutative ring for the function f ∈ F , when the identity Nα + Nβ = Nγ
(N α , N β , N γ ∈ S)
(ii) ((z − c)β · (z − c)α )γ = e−iπγ Q(α, β, γ)
Γ(γ − α − β) Γ(−α − β)
×(z − c)α+β−γ .
(4)
(8)
holds. (Nishimoto, 2003) (III)Lemma. We have (Nishimoto, 1984) (i) ((z − c)β )α = e−iπα
(2)
α
Γ(α − β) (z − c)β−α Γ(−β) Γ(α − β) (| | ≤ ∞) Γ(−β)
(Re(α + β + 1) > 0, (1 + β − γ) ∈ / Z0− ), Γ(γ − α − β) (iii) ((z − c)α+β )γ = e−iπγ (z − c)α+β−γ .(5) Γ(−α − β) where Γ(γ − α − β) z − c = 0, | | < ∞. Γ(−α − β) Proof of ( i ). We have ((z − c)α · (z − c)β )γ =
∞ k=0
Γ(γ + 1) k!Γ(γ + 1 − k)
× ((z − c)α )γ−k ((z − c)β )k
(ii) (log(z − c))α = −eiπα Γ(α)(z − c)−α (|Γ(α)| ≤ ∞)
(6) by Lemma (iv). Next we have
(iii) ((z − c)−α )−α
1 = −eiπα log(z − c), Γ(α) (|Γ(α)| ≤ ∞)
where z − c = 0 in (i), and z − c = 0, 1 in (ii) and (iii) , (iv) (u · v)α :=
∞ k=0
((z − c)α )γ−k = e−iπ(γ−k)
(|
Γ(γ − k − α) | < ∞). Γ(−α)
and ((z − c)β )k = e−iπk
Γ(α + 1) uα−k vk k!Γ(α + 1 − k) (u = u(z), v = v(z))
Γ(γ − k − α) (z − c)α−γ+k (7) Γ(−α)
Γ(k − β) (z − c)β−k Γ(−β)
by Lemma (i), respectively. Substitute (7) and (8) into (6), we have then
(8)
((z − c)α · (z − c)β )γ ∞ Γ(γ + 1)Γ(γ − α − k)Γ(k − β) = e−iπγ k!Γ(γ + 1 − k)Γ(−α)Γ(−β) k=0 α+β−γ
×(z − c) . Γ(γ − α) = e−iπγ (z − c)α+β−γ Γ(−α) ∞ [−β]k [−γ]k × k![1 + α − γ]k
(9)
(10)
k=0
using the relationship Γ(λ + 1 − k) = (−1)−k
Γ(λ + 1)Γ(−λ) Γ(k − λ)
((z − c)α+β )γ = e−iπγ
×(z − c)α+β−γ Γ(γ − α − β) | < ∞) Γ(−α − β) directly by Lemma (i). (|
Note. (u · v)α , (which have · ) means the calculation by the use of generalized Leibniz rule, that is, the use of Lemma (iv).
(11)
[λ]k = λ(λ + 1) · · · (λ + k − 1) = Γ(λ + k)/Γ(λ),
3. N- FRACTIONAL CALCULUS OF PRODUCTS OF SOME LOGARITHMIC FUNCTIONS Theorem 2. When α, β, γ ∈ / Z0+ , we have ;
with [λ]0 = 1. (notation of P ochhammer).
(i)
Therefore, applying the following relationships
k=0
k![c]k
(((log(z − c))−α · (log(z − c))−β )γ = eiπ(α+β−γ) P (α, β, γ)T (α, β, γ)(z − c)α+β−γ
= 2 F1 (a, b; c; 1) =
(1)
Γ(c)Γ(c − a − b) Γ(c − a)Γ(c − b)
(Re(α + β + 1) > 0, (1 + α − γ) ∈ /
(12)
(((log(z − c))−β · (log(z − c))−α )γ
and
= eiπ(α+β−γ) Q(α, β, γ)T (α, β, γ)(z − c)α+β−γ
(λ ∈ / Z)
(13)
(2) (Re(α + β + 1) > 0, (1 + β − γ) ∈ /
to (10), we obtain
×(z − c)α+β−γ
(iii) (((log(z − c))−α · (log(z − c))−β )γ = eiπ(α+β−γ) T (α, β, γ)(z − c)α+β−γ (3) where z − c = 0, 1, T (α, β, γ) = B(−α, −β)Γ(γ − α − β) (|T (α, β, γ)| = M < ∞),
(15) Z0− )
and P (α, β, γ) and Q(α, β, γ) are the ones shown by (1) and (2) , respectively. ( B(* ,* ) ; beta function ). (16)
Proof of ( i ). We have (log(z − c))−α = −eiπα Γ(−α)(z − c)α
We have then (3) from (16) using the notation (1), under the conditions. Proof of ( ii ) . In the same way as the proof of (i) we obtain (4) using (2) instead of (1), under the conditions. ( Simply, changing α and β in (3) we obtain (4), using (2). Proof of ( iii ). We have
Z0− ),
and
((z − c)α · (z − c)β )γ Γ(γ − α) = e−iπγ (z − c)α+β−γ Γ(−α) ×2 F1 (−β, −γ; 1 + α − γ; 1) (14) Γ(γ − α)Γ(1 + α + β)Γ(1 + α − γ) = e−iπγ Γ(−α)Γ(1 + α)Γ(1 + α + β − γ) (Re(α + β + 1) > 0, (1 + α − γ) ∈ / sinπα · sinπ(γ − α − β) = e−iπγ sinπ(α + β) · sinπ(γ − α) Γ(γ − α − β) × (z − c)α+β−γ . Γ(−α − β)
Z0− ),
(ii)
(Re(c − a − b) > 0, c ∈ / Z0− ) π Γ(λ)Γ(1 − λ) = sinπλ
(17)
(uv)α (without · ) means the calculation without the use of generalized Leibniz rule.
where
∞ [a]k [b]k
Γ(γ − α − β) Γ(−α − β)
(4)
(α ∈ / Z0+ ) and (log(z − c))−β = −eiπβ Γ(−β)(z − c)β (β ∈ / Z0+ ) by Lemma (ii) , respectively, hence we obtain
(5)
(((log(z − c))−α · (log(z − c))−β )γ iπ(α+β)
=e
α
β
Γ(−α)Γ(−β)((z − c) · (z − c) )γ(6)
from (4) and (5). Therefore, applylng (3) of section [1] to (6) we obtain (i) clearly, under the conditions. Proof of ( ii ). In the same way described as above, we obtain (ii) under the conditions stated before. Or change the order (log(z − c))α , and (log(z − c))β in (6), then applying (4) in section [1] to it we obtain (ii) clearly, under the conditions. Proof of ( iii ). We have (((log(z − c))−α (log(z − c))−β )γ = eiπ(α+β) Γ(−α)Γ(−β)((z − c)α (z − c)β )γ(7) = eiπ(α+β) Γ(−α)Γ(−β)((z − c)α+β )γ
(8)
applying (4) and (5). Therefore, we obtain (iii) from (8) and (5) of section [1], under the conditions.
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