N-FRACTIONAL CALCULUS OF SOME PRODUCTS OF SOME FUNCTION

N-FRACTIONAL CALCULUS OF SOME PRODUCTS OF SOME FUNCTION

Proceedings of the 2nd IFAC Workshop on Fractional Differentiation and its Applications Porto, Portugal, July 19-21, 2006 N-FRACTIONAL CALCULUS OF SO...

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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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