Journal ArticleDOI

# A higher dimensional fractional Borel‐Pompeiu formula and a related hypercomplex fractional operator calculus

15 Jul 2019--Vol. 42, Iss: 10, pp 3633-3653

AbstractIn this paper we develop a fractional integro-differential operator calculus for Clifford-algebra valued functions. To do that we introduce fractional analogues of the Teodorescu and Cauchy-Bitsadze operators and we investigate some of their mapping properties. As a main result we prove a fractional Borel-Pompeiu formula based on a fractional Stokes formula. This tool in hand allows us to present a Hodge-type decomposition for the fractional Dirac operator. Our results exhibit an amazing duality relation between left and right operators and between Caputo and Riemann-Liouville fractional derivatives. We round off this paper by presenting a direct application to the resolution of boundary value problems related to Laplace operators of fractional order.

### 1 Introduction

• Properties and applications of ∗The final version is published in Mathematical Methods in the Applied Science, in press.
• Additionally, in [4] the authors also investigated some interesting connections between the Teodorescu operator and Hermitian regular functions.
• Actually, in classical three-dimensional vector analysis it is nothing else than the decomposition of an arbitrary sufficiently regular vector field into the sum of a divergence free field (having a vector potential) and a curl free vector field (having a scalar potential).
• In Section 3, the authors present the fundamental solutions of the fractional Laplace and Dirac operators in Rn, defined by left Riemann-Liouville and Caputo fractional derivatives.

### 3 Fundamental solutions revisited

• In [10] and [12] the authors considered the so-called three-parameter fractional Laplace and Dirac operators defined in terms of the left Riemann-Liouville and Caputo fractional derivatives, and obtained families of eigenfunctions and fundamental solutions for both operators.
• For the fractional Dirac operator CDαa+ the authors can obtain a family of fundamental solutions by applying the operator CDαa+ to the family of fundamental solutions of the operator C∆αa+ .
• Now the authors present the corresponding results for the Riemann-Liouville case.

### 4 Fractional Teodorescu and Cauchy-Bitsadze operators

• In this section the authors introduce and study the main properties of the fractional analogues of the classical Teodorescu and Cauchy-Bitsadze operators described in [17].
• Suppose that f and g satisfy the above mentioned conditions, also known as Proof.
• Before the authors deduce two properties of the fractional integral operators (59) and (60), they need to understand the behaviour of their fractional derivatives when the argument of the function over which they apply the derivatives is only translated.
• Concerning (63) the deduction is even more direct because the operator C a+k ∂ 1+αk 2 xk only acts on the functions g0 and g1.

### 5 Hodge-type decomposition

• The aim of this section is to obtain a Hodge-type decomposition and to present an immediate application of this decomposition for the resolution of boundary value problems involving the fractional Laplace operator.
• To realize this the authors need first the following lemma.
• Hence, the intersection of these subspaces only contains the zero function, which implies that the sum is direct.
• Since f ∈ Lq(Ω) was arbitrarily chosen their decomposition is a direct decomposition of the space Lq(Ω).
• The proof is based on applying the properties of the operator CTα and of the projector CQα.

### 6 Conclusion

• In this work the authors presented a generalization of several results of the classical continuous Clifford function theory developed in [17] in the context of fractional Clifford analysis.
• Due to the “double duality” indicated previously, some of the previous results admit alternative versions, for instance, for the operator RLDαa+ .
• Moreover, it is desirable to obtain an explicit expression for the fundamental solutions finding appropriate functions g0 and g1.

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A higher dimensional fractional Borel-Pompeiu formula
and a related hypercomplex fractional operator calculus
M. Ferreira
§,
, R.S. Kraußhar
]
, M.M. Rodrigues
, N. Vieira
§
School of Technology and Management,
Polytechnic Institute of Leiria
P-2411-901, Leiria, Portugal.
E-mail: milton.ferreira@ipleiria.pt
]
Fachgebiet Mathematik,
Erziehungswissenschaftliche Fakult¨at, Universit¨at Erfurt
Nordh¨auserstr. 63, 99089 Erfurt.
E-mail: soeren.krausshar@uni-erfurt.de
CIDMA - Center for Research and Development in Mathematics and Applications
Department of Mathematics, University of Aveiro
Campus Universit´ario de Santiago, 3810-193 Aveiro, Portugal.
E-mails: mferreira@ua.pt, mrodrigues@ua.pt, nloureirovieira@gmail.com
Abstract
In this paper we develop a fractional integro-diﬀerential operator calculus for Cliﬀord-algebra valued
functions. To do that we introduce fractional analogues of the Teodorescu and Cauchy-Bitsadze operators
and we investigate some of their mapping properties. As a main result we prove a fractional Borel-Pompeiu
formula based on a fractional Stokes formula. This tool in hand allows us to present a Hodge-type decom-
position for the fractional Dirac operator. Our results exhibit an amazing duality relation between left and
right operators and between Caputo and Riemann-Liouville fractional derivatives. We round oﬀ this paper
by presenting a direct application to the resolution of boundary value problems related to Laplace operators
of fractional order.
Keywords: Fractional Cliﬀord analysis; Fractional derivatives; Stokes’s formula; Borel-Pompeiu for-
mula; Cauchy’s integral formula; Hodge-type decomposition.
MSC 2010: 35R11; 30G35; 26A33; 35A08; 30E20; 45P05.
1 Introduction
Cliﬀord analysis oﬀers a higher dimensional generalization of the classical theory of complex holomorphic func-
tions. Its tools can be applied to several diﬀerent areas, for instance to quantum mechanics, quantum ﬁeld
theory [15], projective geometry, computer graphics [30], neural network theory [3] and to many other areas
of physics and engineering [17]. The corresponding analogy of the class of complex holomorphic functions is
that of monogenic functions. These are the null solutions to the Dirac operator. The latter operator factorizes
the Laplace operator and provides a ﬁrst order generalization of the well-known Cauchy-Riemann operator in
complex analysis (see [5,8]).
A main tool that Cliﬀord holomorphic function theory uses in the treatment of boundary value problems
is the Teodorescu operator, which is the right inverse of the Dirac operator. Properties and applications of
The ﬁnal version is published in Mathematical Methods in the Applied Science, in press. It as available via the website: ???.
1

the hypercomplex Teodorescu operator have been studied by many authors (see for instance [29] for a list of
references). In the context of quaternionic and Cliﬀord analysis, K. urlebeck and W. Spr¨oßig studied among
many others particular mapping and regularity properties of this integral operator. Furthermore, they studied
its connections to elliptic boundary value problems (see [17]). Additionally, in [4] the authors also investigated
some interesting connections between the Teodorescu operator and Hermitian regular functions. An extension
to the time-dependent case addressing the heat and the Schr¨odinger operator has been presented subsequentially
in [6].
Another central aspect that appears in the classical vector calculus and in generalized Cliﬀord holomorphic
function theories is the Helmholtz decomposition of L
2
-spaces. Actually, in classical three-dimensional vector
analysis it is nothing else than the decomposition of an arbitrary suﬃciently regular vector ﬁeld into the sum
of a divergence free ﬁeld (having a vector potential) and a curl free vector ﬁeld (having a scalar potential).
This particular space decomposition together with the Teodorescu operator calculus provides a very elegant
resolution toolkit for boundary value problems in the corresponding scales of Hilbert-Sobolev spaces. For more
details we also refer to the survey paper [27]. For the time-dependent case, see for instance [7, 22, 23].
A parallel development over the last years consists of a rapidly increasing interest in the theory of derivatives
and integrals of non-integer order. Apart from several applications of fractional order models, as for example,
to kinetic theories, statistical mechanics, to the dynamics in complex media, and to many other ﬁelds (see [28]
and the references indicated therein), those methods provide an important counterpart and extension of the
classical integer order models. The advantage of fractional models consists in the possibility of using fractional
derivatives to describe the memory and hereditary properties of various materials and processes. Another ﬁeld
of application consists in addressing diﬀerential equations related to ﬂows with permeable boundaries, such
as for instance dam-ﬁll problems which provides a further important motivation to develop three-dimensional
generalizations of harmonic and Cliﬀord analysis tools for the fractional setting. Preceding work pointing in
this direction can be found in [18,19] where the fractional p-Laplace equation has been treated.
Behind this background, the development of links between Cliﬀord analysis and fractional diﬀerential calcu-
lus represents a very recent topic of research. In particular, some ﬁrst steps in the direction of an introduction
of a fractional Cliﬀord analytic function theory have been made in [10–12, 14]. In these papers, the authors
determined series representations for the fundamental solution related to some stationary and non-stationary
fractional Dirac-type operators. The knowledge of explicit representation formulas of these fundamental so-
lutions represents a corner stone in the development of a fractional version of Cliﬀord analysis. The latter
functions serve as kernels for fractional integral operators, such as the fractional Teodorescu operator that we
are going to introduce and to investigate in this paper.
The aim of this paper is to apply the fundamental solutions obtained in [10, 12] in order to develop the
fundamentals of a fractional operator calculus related to the fractional Dirac operator that depends on a vector
of fractional parameters α = (α
1
, . . . , α
n
) with α
i
]0, 1], i = 1, . . . , n. We introduce fractional analogues of
the Teodorescu operator and of the Cauchy-Bitsadze operator, and we investigate some important mapping
properties. Moreover, we present a Hodge-type decomposition for the fractional Dirac operator deﬁned via
left Caputo fractional derivatives. The results that we obtain exhibit an amazingly interesting “double duality”
between left and right operators and between Caputo and Riemann-Liouville fractional derivatives. This double
duality appears in a non-trivial generalization of the Stokes formula as well as in the fractional Borel-Pompeiu
formula and in the Hodge-type decomposition that we are going to present subsequentially. Throughout the
paper we show that we can always re-obtain the results of the classical function theory for the Dirac operator
when switching to the limit case when α = (1, . . . , 1). The analogous of the results presented in this paper for
the case of the time-fractional parabolic Dirac operator can be found in [13].
The structure of the paper reads as follows. In the Preliminaries section we recall some basic deﬁnitions
from the fractional calculus, special functions, and Cliﬀord analysis. In Section 3, we present the fundamental
solutions of the fractional Laplace and Dirac operators in R
n
, deﬁned by left Riemann-Liouville and Caputo
fractional derivatives. Moreover, we prove that these functions belong to the function space L
1
(Ω) under certain
conditions. Throughout the whole paper we assume that is a bounded open rectangular domain. In Section
4, we introduce and study the main properties of the fractional analogues of the Teodorescu operator and of the
Cauchy-Bitsadze operator. Finally, in Section 5 we present a Hodge-type decomposition for the L
q
-space, where
one of the components is the kernel of the fractional Dirac operator deﬁned in terms of left Caputo fractional
2

derivatives. This decomposition represents a main result in the paper apart from proving the generalizations of
the Borel-Pompeiu formulae in the context of Caputo derivatives. In the analysis of the mapping properties and
the regularity properties there still appear some further peculiarities that require special attention. We round
oﬀ this paper by giving an immediate application to the resolution of boundary value problems involving the
fractional Laplace operators.
2 Preliminaries
2.1 Fractional calculus and special functions
Let a, b R with a < b let α > 0. The left and right Riemann-Liouville fractional integrals I
α
a
+
and I
α
b
of order
α are given by (see [21])
(I
α
a
+
f) (x) =
1
Γ(α)
Z
x
a
f(t)
(x t)
1α
dt, x > a (1)
(I
α
b
f) (x) =
1
Γ(α)
Z
b
x
f(t)
(t x)
1α
dt, x < b. (2)
By
RL
D
α
a
+
and
RL
D
α
b
we denote the left and right Riemann-Liouville fractional derivatives of order α > 0 on
[a, b] R, which are deﬁned by (see [21])
RL
D
α
a
+
f
(x) =
D
m
I
mα
a
+
f
(x) =
1
Γ(m α)
d
m
dx
m
Z
x
a
f(t)
(x t)
αm+1
dt, x > a (3)
RL
D
α
b
f
(x) = (1)
m
D
m
I
mα
b
f
(x) =
(1)
m
Γ(m α)
d
m
dx
m
Z
b
x
f(t)
(t x)
αm+1
dt, x < b. (4)
Here, m = [α] + 1 and [α] means the integer part of α. Let
C
D
α
a
+
and
C
D
α
b
denote, respectively, the left and
right Caputo fractional derivative of order α > 0 on [a, b] R, which are deﬁned by (see [21])
C
D
α
a
+
f
(x) =
I
mα
a
+
D
m
f
(x) =
1
Γ(m α)
Z
x
a
f
(m)
(t)
(x t)
αm+1
dt, x > a (5)
C
D
α
b
f
(x) = (1)
m
I
mα
b
D
m
f
(x) =
(1)
m
Γ(m α)
Z
b
x
f
(m)
(t)
(t x)
αm+1
dt, x < b. (6)
We denote by I
α
a
+
(L
1
) the class of functions f that are represented by the fractional integral (1) of a summable
function, that is f = I
α
a
+
ϕ, with ϕ L
1
(a, b). A description of this class of functions is given in [26].
Theorem 2.1 (cf. [26]) A function f belongs to I
α
a
+
(L
1
), α > 0, if and only if I
mα
a
+
f belongs to AC
m
([a, b]),
m = [α] + 1 and (I
mα
a
+
f)
(k)
(a) = 0, k = 0, . . . , m 1.
In Theorem 2.1, AC
m
([a, b]) denotes the class of functions f which are continuously diﬀerentiable on the segment
[a, b] up to the order m 1 and f
(m1)
is supposed to be absolutely continuous on [a, b]. We note that the
conditions (I
mα
a
+
f)
(k)
(a) = 0, k = 0, . . . , m1, imply that f
(k)
(a) = 0, k = 0, . . . , m1 (see [25,26]). Removing
the last condition in Theorem 2.1 we obtain the class of functions that admit a summable fractional derivative.
Deﬁnition 2.2 (see [26]) A function f L
1
(a, b) has a summable fractional derivative
D
α
a
+
f
(x) if
I
mα
a
+
f
(x)
belongs to AC
m
([a, b]), where m = [α] + 1.
If a function f admits a summable fractional derivative, then we have the following composition rules (see [26]
and [25], respectively)
I
α
a
+
RL
D
α
a
+
f
(x) = f(x)
m1
X
k=0
(x a)
αk1
Γ(α k)
I
mα
a
+
f
(mk1)
(a), m = [α] + 1 (7)
I
α
a
+
C
D
α
a
+
f
(x) = f(x)
m1
X
k=0
f
(k)
(a)
k!
(x a)
k
, m = [α] + 1. (8)
3

We remark that if f I
α
a
+
(L
1
) then (7) and (8) reduce to
I
α
a
+
RL
D
α
a
+
f
(x) =
I
α
a
+
C
D
α
a
+
f
(x) = f(x). Nev-
ertheless we note that D
α
a
+
I
α
a
+
f = f in both cases. This is a particular case of a more general property
(cf. [25, (2.114)])
D
α
a
+
I
γ
a
+
f
= D
αγ
a
+
f, α γ > 0. (9)
One important function used in this paper is the two-parameter Mittag-Leﬄer function E
µ,ν
(z) (see [16]),
which is deﬁned in terms of the power series by
E
µ,ν
(z) =
X
n=0
z
n
Γ(µn + ν)
, µ > 0, ν > 0, z C. (10)
In particular, the function E
µ,ν
(z) is entire of order ρ =
1
µ
and type σ = 1. From the power series (10) and the
operators (1), (3) and (5), we can obtain by straightforward calculations the following fractional integral and
diﬀerential formulae involving E
µ,ν
(z) (see [16, pp. 87-88]):
I
α
a
+
(x a)
ν1
E
µ,ν
(k(x a)
µ
)
= (x a)
α+ν1
E
µ,ν+α
(k(x a)
µ
) (11)
for all α > 0, k C, x > a, µ > 0, ν > 0,
RL
D
α
a
+
(x a)
ν1
E
µ,ν
(k(x a)
µ
)
= (x a)
να1
E
µ,να
(k(x a)
µ
) (12)
for all α > 0, k C, x > a, µ > 0, ν > 0, ν 6= α p, where p = 0, . . . , m 1 with m = [α] + 1, and
C
D
α
a
+
(x a)
ν1
E
µ,ν
(k(x a)
µ
)
= (x a)
να1
E
µ,να
(k(x a)
µ
) (13)
for all α > 0, k C, x > a, µ > 0, ν > 0, ν 6= p, where p = 1, . . . , m with m = [α] + 1.
Remark 2.3 For ν = α p with p = 0, . . . , m 1, we have that
RL
D
α
a
+
((x a)
αp1
) = 0 which implies that
the ﬁrst term in the series expansion of (x a)
ν1
E
µ,ν
(k(x a)
µ
) vanishes. Therefore, the derivation rule (12)
must be replaced in these cases by the following derivation rule:
RL
D
α
a
+
(x a)
αp1
E
µ,αp
(k(x a)
µ
)
= (x a)
µp1
k E
µ,µp
(k(x a)
µ
) , p = 0, . . . , m 1. (14)
Remark 2.4 For ν = p with p = 1, . . . , m, we have that
C
D
α
a
+
((x a)
p1
) = 0 which implies that the ﬁrst
term in the series expansion of (x a)
ν1
E
µ,ν
(k(x a)
µ
) vanishes. Therefore, the derivation rule (13) must
be replaced in these cases by the following derivation rule:
C
D
α
a
+
(x a)
p1
E
µ,p
(k(x a)
µ
)
= (x a)
µ+pα1
k E
µ,µ+pα
(k(x a)
µ
) , p = 1, . . . , m. (15)
The approach presented in this paper is based on the Laplace transform and leads to the solution of a linear
Abel integral equation of the second kind.
Theorem 2.5 ( [16, Thm. 4.2]) Let f L
1
[a, b], α > 0 and λ C. Then the integral equation
u(x) = f(x) +
λ
Γ(α)
Z
x
a
(x t)
α1
u(t) dt, x [a, b]
has a unique solution
u(x) = f(x) + λ
Z
x
a
(x t)
α1
E
α,α
(λ(x t)
α
)f(t) dt. (16)
Now we recall the formula for fractional integration by parts for 0 < α < 1 and x [a, b] (see [1])
Z
b
a
g(x)
C
D
α
a
+
f
(x) dx =
Z
b
a
f(x)
RL
D
α
b
g
(x) dx + [f(x) (I
α
b
g) (x)]
b
a
,
Z
b
a
g(x)
C
D
α
b
f
(x) dx =
Z
b
a
f(x)
RL
D
α
a
+
g
(x) dx [f(x) I
α
a
+
g(x)]
b
a
.
We end this section by recalling an important result about the boundedness of the fractional integrals I
α
a
+
and
I
α
b
(see Theorem 3.5 in [26]).
Theorem 2.6 If 0 < α < 1 and 1 < p <
1
α
then the operators I
α
a
+
and I
α
b
are bounded from L
p
(a, b) into
L
q
(a, b), where q =
p
1αp
and [a, b] R.
4

2.2 Cliﬀord analysis
Let {e
1
, ··· , e
n
} be the standard basis of the Euclidean vector space in R
n
. The associated Cliﬀord algebra
R
0,n
is the free algebra generated by R
n
modulo x
2
= −||x||
2
e
0
, where x R
n
and e
0
is the neutral element
with respect to the multiplication operation in the Cliﬀord algebra R
0,n
. The deﬁning relation induces the
multiplication rules
e
i
e
j
+ e
j
e
i
= 2δ
ij
, (17)
where δ
ij
denotes the Kronecker’s delta. In particular, e
2
i
= 1 for all i = 1, . . . , n. The standard basis vectors
thus operate as imaginary units. A vector space basis for R
0,n
is given by the set {e
A
: A {1, . . . , n}} with
e
A
= e
l
1
e
l
2
. . . e
l
r
, where 1 l
1
< . . . < l
r
n, 0 r n, e
:= e
0
:= 1. Each a R
0,n
can be written in the
form a =
P
A
a
A
e
A
, with a
A
R. The conjugation in the Cliﬀord algebra R
0,n
is deﬁned by a =
P
A
a
A
e
A
,
where e
A
= e
l
r
e
l
r1
. . . e
l
1
, and e
j
= e
j
for j = 1, . . . , n, e
0
= e
0
= 1. Each non-zero vector a R
n
has a
multiplicative inverse given by
a
||a||
2
.
An R
0,n
valued function f over R
n
has the representation f =
P
A
e
A
f
A
with components f
A
:
R
0,n
. Properties such as continuity or diﬀerentiability have to be understood componentwise. Next, we recall
the Euclidean Dirac operator D =
P
n
j=1
e
j
x
j
. This operator satisﬁes D
2
= ∆, where is the n-dimensional
Euclidean Laplacian. An R
0,n
-valued function f is called left-monogenic if it satisﬁes Du = 0 on (resp.
right-monogenic if it satisﬁes uD = 0 on Ω).
For more details about Cliﬀord algebras and basic concepts of its associated function theory we refer the
interested reader for example to [8].
3 Fundamental solutions revisited
In [10] and [12] the authors considered the so-called three-parameter fractional Laplace and Dirac operators
deﬁned in terms of the left Riemann-Liouville and Caputo fractional derivatives, and obtained families of
eigenfunctions and fundamental solutions for both operators. In this section we present the generalization of
these results for R
n
. Let =
Q
n
i=1
]a
i
, b
i
[ be any bounded open rectangular domain, let α = (α
1
, . . . , α
n
), with
α
i
]0, 1], i = 1, . . . , n, and let us consider the n-parameter fractional Laplace operators
RL
α
a
+
and
C
α
a
+
deﬁned over by means of the left Riemann-Liouville and left Caputo fractional derivatives, respectively, given
by
RL
α
a
+
=
n
X
i=1
RL
a
+
i
1+α
i
x
i
,
C
α
a
+
=
n
X
i=1
C
a
+
i
1+α
i
x
i
. (18)
Associated to them there are the corresponding fractional Dirac operators
RL
D
α
a
+
and
C
D
α
a
+
deﬁned by
RL
D
α
a
+
=
n
X
i=1
e
i
RL
a
+
i
1+α
i
2
x
i
,
C
D
α
a
+
=
n
X
i=1
e
i
C
a
+
i
1+α
i
2
x
i
. (19)
For i = 1, . . . , n the partial derivatives
RL
a
+
i
1+α
i
x
i
,
RL
a
+
i
1+α
i
2
x
i
,
C
a
+
i
1+α
i
x
i
and
C
a
+
i
1+α
i
2
x
i
are the left Riemann-Liouville
and Caputo fractional derivatives (3) and (5) of orders 1 + α
i
and
1+α
i
2
, with respect to the variable x
i
]a
i
, b
i
[.
Under certain conditions we have that
RL
α
a
+
=
RL
D
α
a
+
RL
D
α
a
+
(see [10]), and
C
α
a
+
=
C
D
α
a
+
C
D
α
a
+
(see
[12]). Due to the nature of the eigenfunctions and the fundamental solution of these operators we additionally
need to consider the variable bx = (x
2
, . . . , x
n
)
b
=
Q
n
i=2
]a
i
, b
i
[, and the fractional Laplace and Dirac operators
acting on bx deﬁned by
RL
b
α
a
+
=
n
X
i=2
RL
a
+
i
1+α
i
x
i
,
C
b
α
a
+
=
n
X
i=2
C
a
+
i
1+α
i
x
i
,
RL
b
D
α
a
+
=
n
X
i=2
e
i
RL
a
+
i
1+α
i
2
x
i
,
C
b
D
α
a
+
=
n
X
i=2
e
i
C
a
+
i
1+α
i
2
x
i
. (20)
We start by addressing the Caputo case. Consider the eigenfunction problem
C
α
a
+
v(x) = λv(x), (21)
5

##### Citations
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Book ChapterDOI
01 Jan 2015

2,819 citations

Journal ArticleDOI
10 Sep 2021
Abstract: In this work, we investigate analytically the solutions of a nonlinear div-curl system with fractional derivatives of the Riemann–Liouville or Caputo types. To this end, the fractional-order vector operators of divergence, curl and gradient are identified as components of the fractional Dirac operator in quaternionic form. As one of the most important results of this manuscript, we derive general solutions of some non-homogeneous div-curl systems that consider the presence of fractional-order derivatives of the Riemann–Liouville or Caputo types. A fractional analogous to the Teodorescu transform is presented in this work, and we employ some properties of its component operators, developed in this work to establish a generalization of the Helmholtz decomposition theorem in fractional space. Additionally, right inverses of the fractional-order curl, divergence and gradient vector operators are obtained using Riemann–Liouville and Caputo fractional operators. Finally, some consequences of these results are provided as applications at the end of this work.

3 citations

Posted Content
Abstract: Quaternionic analysis relies heavily on results on functions defined on domains in $\mathbb R^4$ (or $\mathbb R^3$) with values in $\mathbb H$. This theory is centered around the concept of $\psi-$hyperholomorphic functions i.e., null-solutions of the $\psi-$Fueter operator related to a so-called structural set $\psi$ of $\mathbb H^4$. Fractional calculus, involving derivatives-integrals of arbitrary real or complex order, is the natural generalization of the classical calculus, which in the latter years became a well-suited tool by many researchers working in several branches of science and engineering. In theoretical setting, associated with a fractional $\psi-$Fueter operator that depends on an additional vector of complex parameters with fractional real parts, this paper establishes a fractional analogue of Borel-Pompeiu formula as a first step to develop a fractional $\psi-$hyperholomorphic function theory and the related operator calculus.

1 citations

Journal ArticleDOI

1 citations

Journal ArticleDOI
Abstract: In this paper, we study the fundamental solution of natural powers of the n-parameter fractional Laplace and Dirac operators defined via Riemann–Liouville fractional derivatives. To do this we use iteration through the fractional Poisson equation starting from the fundamental solutions of the fractional Laplace $$\Delta _{a^+}^\alpha$$ and Dirac $$D_{a^+}^\alpha$$ operators, admitting a summable fractional derivative. The family of fundamental solutions of the corresponding natural powers of fractional Laplace and Dirac operators are expressed in operator form using the Mittag–Leffler function.

1 citations

##### References
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Book
02 Mar 2006
Abstract: 1. Preliminaries. 2. Fractional Integrals and Fractional Derivatives. 3. Ordinary Fractional Differential Equations. Existence and Uniqueness Theorems. 4. Methods for Explicitly solving Fractional Differential Equations. 5. Integral Transform Methods for Explicit Solutions to Fractional Differential Equations. 6. Partial Fractional Differential Equations. 7. Sequential Linear Differential Equations of Fractional Order. 8. Further Applications of Fractional Models. Bibliography Subject Index

10,654 citations

### "A higher dimensional fractional Bor..." refers background or methods in this paper

• ...By D a+ and D b− we denote the left and right Riemann-Liouville fractional derivatives of order α > 0 on [a, b] ⊂ R, which are defined by (see [21]) ( D a+f ) (x) = ( DmIm−α a+ f ) (x) = 1 Γ(m− α) d dxm ∫ x...

[...]

• ...Let D a+ and D b− denote, respectively, the left and right Caputo fractional derivative of order α > 0 on [a, b] ⊂ R, which are defined by (see [21]) ( D a+f ) (x) = ( Im−α a+ D f ) (x) = 1 Γ(m− α) ∫ x...

[...]

• ...Taking into account its convolution and operational properties (see [9,21]), we obtain the following relations for each term in (22):...

[...]

• ...The left and right Riemann-Liouville fractional integrals I a+ and I α b− of order α are given by (see [21])...

[...]

Book
08 Dec 1993
Abstract: Fractional integrals and derivatives on an interval fractional integrals and derivatives on the real axis and half-axis further properties of fractional integrals and derivatives other forms of fractional integrals and derivatives fractional integrodifferentiation of functions of many variables applications to integral equations of the first kind with power and power-logarithmic kernels integral equations fo the first kind with special function kernels applications to differential equations.

6,805 citations

### "A higher dimensional fractional Bor..." refers background in this paper

• ...4 in [26]), leads to ∥∥∥∥ C a+k 1+αk 2 xk (CTαg) ∥∥∥∥ Lq(Ω) = ∥∥∥∥( C a+k 1+αk 2 xk G + ) ∗ g ∥∥∥∥ Lq(Ω) ≤ ∥∥∥∥ C a+k 1+αk 2 xk G + ∥∥∥∥ L1(Ω) ‖g‖Lq(Ω)...

[...]

• ...If a function f admits a summable fractional derivative, then we have the following composition rules (see [26] and [25], respectively) ( I a+ D a+f ) (x) = f(x)− m−1 ∑...

[...]

• ...2 (see [26]) A function f ∈ L1(a, b) has a summable fractional derivative ( D a+f ) (x) if ( Im−α a+ f ) (x) belongs to AC([a, b]), where m = [α] + 1....

[...]

• ...[26]) A function f belongs to I a+(L1), α > 0, if and only if I m−α a+ f belongs to AC ([a, b]), m = [α] + 1 and (Im−α a+ f) (a) = 0, k = 0, ....

[...]

• ...A description of this class of functions is given in [26]....

[...]

Book
01 Jan 1999
Abstract: Preface. Acknowledgments. Special Functions Of Preface. Acknowledgements. Special Functions of the Fractional Calculus. Gamma Function. Mittag-Leffler Function. Wright Function. Fractional Derivatives and Integrals. The Name of the Game. Grunwald-Letnikov Fractional Derivatives. Riemann-Liouville Fractional Derivatives. Some Other Approaches. Sequential Fractional Derivatives. Left and Right Fractional Derivatives. Properties of Fractional Derivatives. Laplace Transforms of Fractional Derivatives. Fourier Transforms of Fractional Derivatives. Mellin Transforms of Fractional Derivatives. Existence and Uniqueness Theorems. Linear Fractional Differential Equations. Fractional Differential Equation of a General Form. Existence and Uniqueness Theorem as a Method of Solution. Dependence of a Solution on Initial Conditions. The Laplace Transform Method. Standard Fractional Differential Equations. Sequential Fractional Differential Equations. Fractional Green's Function. Definition and Some Properties. One-Term Equation. Two-Term Equation. Three-Term Equation. Four-Term Equation. Calculation of Heat Load Intensity Change in Blast Furnace Walls. Finite-Part Integrals and Fractional Derivatives. General Case: n-term Equation. Other Methods for the Solution of Fractional-order Equations. The Mellin Transform Method. Power Series Method. Babenko's Symbolic Calculus Method. Method of Orthogonal Polynomials. Numerical Evaluation of Fractional Derivatives. Approximation of Fractional Derivatives. The "Short-Memory" Principle. Order of Approximation. Computation of Coefficients. Higher-order Approximations. Numerical Solution of Fractional Differential Equations. Initial Conditions: Which Problem to Solve? Numerical Solution. Examples of Numerical Solutions. The "Short-Memory" Principle in Initial Value Problems for Fractional Differential Equations. Fractional-Order Systems and Controllers. Fractional-Order Systems and Fractional-Order Controllers. Example. On Viscoelasticity. Bode's Analysis of Feedback Amplifiers. Fractional Capacitor Theory. Electrical Circuits. Electroanalytical Chemistry. Electrode-Electrolyte Interface. Fractional Multipoles. Biology. Fractional Diffusion Equations. Control Theory. Fitting of Experimental Data. The "Fractional-Order" Physics? Bibliography. Tables of Fractional Derivatives. Index.

3,556 citations

### "A higher dimensional fractional Bor..." refers methods in this paper

• ..., xn) to (68), taking into account the relations (24) to (28), and multiplying by ∏n p=2 s 1+αp p , we obtain the following second kind homogeneous integral equation of Volterra type:...

[...]

Book ChapterDOI
01 Jan 2015

2,819 citations

### "A higher dimensional fractional Bor..." refers background in this paper

• ...If a function f admits a summable fractional derivative, then we have the following composition rules (see [26] and [25], respectively) ( I a+ D a+f ) (x) = f(x)− m−1 ∑...

[...]

BookDOI
01 Jan 1992

787 citations