5
Comparison of Definition of Several Fractional Derivatives Yun Ouyang 1, a and Wusheng Wang 1, b* 1 School of Mathematics and Statistics, Hechi University, Guangxi, Yizhou 546300, P. R. China a [email protected], b [email protected] *The corresponding author Keywords: Riemann-liouville fractional derivatives; Caputo's fractional derivative; Grunwald-letnikov fractional derivatives; Fractional integral. Abstract. The idea of fractional derivatives was raised first by L'Hospital in 1695. The fractional calculus and its mathematical consequences attracted many mathematicians such as Fourier, Euler, Laplace. Various definitions of non-integer order integral or derivative was given by many mathematicians. In this paper, firstly, we discuss the positive integer higher order derivative of a function, and obtain general formula of high order derivative. Secondly, we introduce the definitions of Gr\"unwald-Letnikov, Riemann-Liouville and Caputo. Finally, we point out the relationship between these definitions. Caputo's integral definition and Gr\"unwald-Letnikov integral definition are consistent with the Riemann-Liouville integral definition. When f has 1 m order continuous derivative and 1 m p m , Gr\"unwald-Letnikov positive non-integer order derivative definition is consistent with the Riemann-Liouville positive non-integer order derivative definition. Introduction The idea of fractional derivatives was raised first by L'Hospital in 1695. The fractional calculus and its mathematical consequences attracted many mathematicians such as Fourier, Euler, Laplace. Various definitions of non-integer order integral or derivative was given by many mathematicians (see [1]). For fractional derivative, the most popular definitions are Riemann- Liouville and Caputo definitions as follows, respectively. Recently, the fractional calculus methods have become increasingly more popular and successful in a large number of physical applications (see for example, [2, 3]). The theoretical and experimental scientists observed that certain materials admit anomalous, fractional behavior, as [4]. There are many systems which evolution is governed by some fractional differential equations (for example, [5]). Fractional calculus is nowadays a broad and interesting field of very active research (see [6-12]). In this paper, firstly, we discuss the positive integer high order derivative of a function, and obtain general formula of high order derivative. Secondly, we introduce the definitions of Gr\" unwald-Letnikov, Riemann-Liouville and Caputo. Finally, we point out the relationship between these definitions. General Formula of High Order Derivative Suppose that function ) (t f has n order continuous differentiable derivative on ] , [ b a . From the definition of the derivative, we have h h t f t f dt df t f h ) ( ) ( lim ) ( ' 0 , (1) h h t f t f dt f d t f h ) ( ' ) ( ' lim ) ( ' ' 0 2 2 2016 6th International Conference on Education, Management and Computer Science (ICEMC 2016) © 2016. The authors - Published by Atlantis Press 553

Yun Ouyang1, a and Wusheng Wang1, b*Comparison of Definition of Several Fractional Derivatives Yun Ouyang1, a and Wusheng Wang1, b* 1 School of Mathematics and Statistics, Hechi University,

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  • Comparison of Definition of Several Fractional Derivatives

    Yun Ouyang1, a and Wusheng Wang1, b* 1School of Mathematics and Statistics, Hechi University, Guangxi, Yizhou 546300, P. R. China

    [email protected],

    [email protected]

    *The corresponding author

    Keywords: Riemann-liouville fractional derivatives; Caputo's fractional derivative; Grunwald-letnikov fractional derivatives; Fractional integral.

    Abstract. The idea of fractional derivatives was raised first by L'Hospital in 1695. The fractional

    calculus and its mathematical consequences attracted many mathematicians such as Fourier, Euler,

    Laplace. Various definitions of non-integer order integral or derivative was given by many

    mathematicians. In this paper, firstly, we discuss the positive integer higher order derivative of a

    function, and obtain general formula of high order derivative. Secondly, we introduce the definitions of

    Gr\"unwald-Letnikov, Riemann-Liouville and Caputo. Finally, we point out the relationship between

    these definitions. Caputo's integral definition and Gr\"unwald-Letnikov integral definition are

    consistent with the Riemann-Liouville integral definition. When f has 1m order continuous

    derivative and 1 mpm , Gr\"unwald-Letnikov positive non-integer order derivative definition is

    consistent with the Riemann-Liouville positive non-integer order derivative definition.

    Introduction

    The idea of fractional derivatives was raised first by L'Hospital in 1695. The fractional calculus and its

    mathematical consequences attracted many mathematicians such as Fourier, Euler, Laplace. Various

    definitions of non-integer order integral or derivative was given by many mathematicians (see [1]). For

    fractional derivative, the most popular definitions are Riemann- Liouville and Caputo definitions as

    follows, respectively. Recently, the fractional calculus methods have become increasingly more

    popular and successful in a large number of physical applications (see for example, [2, 3]). The

    theoretical and experimental scientists observed that certain materials admit anomalous, fractional

    behavior, as [4]. There are many systems which evolution is governed by some fractional differential

    equations (for example, [5]). Fractional calculus is nowadays a broad and interesting field of very

    active research (see [6-12]).

    In this paper, firstly, we discuss the positive integer high order derivative of a function, and obtain

    general formula of high order derivative. Secondly, we introduce the definitions of Gr\"

    unwald-Letnikov, Riemann-Liouville and Caputo. Finally, we point out the relationship between these

    definitions.

    General Formula of High Order Derivative

    Suppose that function )(tf has n order continuous differentiable derivative on ],[ ba . From the

    definition of the derivative, we have

    h

    htftf

    dt

    dftf

    h

    )()(lim)('

    0

    , (1)

    h

    htftf

    dt

    fdtf

    h

    )(')('lim)(''

    02

    2

    2016 6th International Conference on Education, Management and Computer Science (ICEMC 2016)

    © 2016. The authors - Published by Atlantis Press 553

  • h

    htfhtf

    h

    htftf

    hh

    )2()()()(1lim

    0

    20

    )2()(2)(lim

    h

    htfhtftf

    h

    , (2)

    By induction we can obtain

    ),()1(1

    lim)(0

    0

    )( rhtfr

    n

    hdt

    fdtf

    n

    r

    r

    nhn

    nn

    (3)

    where n is a natural number,

    !

    )1()2)(1(

    r

    rnnnn

    r

    n

    (4)

    Let p be any arbitrary integer, define a new derivative (see [9,10])

    0

    0

    lim ( 1)n

    p p r

    a th

    rnh t a

    pD f t h f t rh

    r

    , (5)

    where nath /)( ,

    !

    )1()2)(1(

    r

    rpppp

    r

    p

    . (6)

    If ,0p let ,pq

    !

    )1()2)(1(

    r

    rqqqq

    r

    q

    , (7)

    then

    r

    q

    r

    rqqqq

    r

    pr)1(

    !

    )1()2)(1( , (8)

    or,

    r

    q

    r

    pr)1( . (9)

    From (5) and (9), we have

    0

    0

    lim , 0, 0.n

    q q

    a th

    rnh t a

    qD f t h f t rh p q p

    r

    (10)

    In particular, we have

    10

    0

    1lim

    n

    a th

    rnh t a

    D f t h f t rhr

    00

    0

    lim ,n t a t

    ahrnh t a

    h f t rh f t s ds f s ds

    (11)

    554

  • 2 2 20 0

    0 0

    2lim lim 1

    n n

    a th h

    r rnh t a nh t a

    D f t h f t rh h r f t rhr

    1

    001

    lim ,n t a t

    ahrnh t a

    h rh f t h rh sf t s ds t f d

    (12)

    3 3 30 0

    0 0

    3 1 2lim lim

    2!

    n n

    a th h

    r rnh t a nh t a

    r rD f t h f t rh h f t rh

    r

    21 1

    2

    0 01 1

    lim lim2! 2!

    n n

    h hr rnh t a nh t a

    h hrh f t h rh rh f t h rh

    22

    0

    1 1,

    2! 3

    t a t

    as f t s ds t f d

    (13)

    Generally, for any positive integer p , define the p order derivative of a function )(tf

    0 0

    0 0

    1 2 1lim lim

    !

    n np p p

    a th h

    r rnh t a nh t a

    p p p p p rD f t h f t rh h f t rh

    r r

    00

    1 2 1lim

    ( 1)!

    np

    hrnh t a

    p p p p rh f t rh

    p

    11

    01

    lim1 !

    np

    hrnh t a

    hrh f t h rh

    p

    2 12

    0 01 0

    lim lim2 2 !

    n np p

    h hr rnh t a nh t a

    phrh f t h rh h f t rh

    p

    11

    0

    1 1.

    1 !

    t a t pp

    as f t s ds t f d

    p p

    (14)

    Since

    2 11 .

    -1

    t pp p

    a t a ta

    dD f t t f d D f t

    dt p

    (15)

    Then

    1 2t t s

    p p p

    a t a t a ta a a

    D f t D f s ds ds D f d

    1 2 1 13

    1 2 3 3 1 2 .pt t t t t tp

    a t p pa a a a a adt dt D f t dt dt dt f t dt

    (16) It implies that the derivative of negative integer p- order and the p-fold integral (2.21) of the

    continuous function )(tf are equivalent.

    Several Fractional Derivatives

    Grunwald-Letnikov fractional derivative and integral definitions (see [9,10]): Let p be any arbitrary

    positive real number, define p order derivative and p order integral of a continuous function )(tf :

    0

    0

    lim -1)n

    G p p ra t

    hrnh t a

    pD f t h f t rh

    r

    ( , (17)

    and

    555

  • 0

    0

    limn

    G p pa t

    hrnh t a

    pD f t h f t rh

    r

    . (18)

    Riemann-Liouville fractional derivative and integral definitions (see [9]): Let m be positive integer,

    1 mpm , define Riemann-Liouville p order derivative and p order integral of a continuous

    function )(tf : 1

    ( ) ( ) ( ) ,

    mt

    R p m p

    a ta

    dD f t t f d

    dt

    (19)

    and

    11( ) ( ) ( ) .( )

    tR p p

    a ta

    D f t t f dp

    (20)

    Define Caputo's fractional derivative and integral definitions(see [9]): Suppose that )(tf

    has m order

    continuous derivative, define Caputo's p order derivative and p order integral: ( )

    1

    1 ( ),( 1 )

    ( ) ( )

    mt

    C p

    a t p ma

    fD d m p m

    m p t

    , (21)

    and

    11( ) ( ) ( ) .( )

    tC p p

    a ta

    D f t t f dp

    (22)

    Comparison of the Definition of Riemann-Liouville, Caputo and Grunwald-Letnikov

    Caputo's integral definition and Grunwald-Letnikov integral definition are consistent with the

    Riemann-Liouville integral definition

    11( )= ( )= ( ) ( ) ( ) .( )

    tG p R p C p p

    a a at t ta

    D f t D f t D f t t f dp

    (23)

    When p is positive integer and ),,2,1(0)()( pkaf k , Caputo's derivative definition and

    Grunwald-Letnikov derivative definition are consistent with the Riemann-Liouville derivative

    definition. ( )= = ( )G p R p C p pa t a t a tD D D f t . (24)

    If )(tf

    has 1m order continuous derivative and 1 mpm , then

    1

    ( ) ( ) ( )

    mt

    R p m p

    a ta

    dD f t t f d

    dt

    ( )( 1)

    0

    ( )( ) 1( ) ( )

    ( 1) ( 1)

    k p km tm p m

    ak

    f a t at f d

    p k p m

    ( ), 1.G pa tD f t m p m (25)

    It implies that Grunwald-Letnikov positive non-integer order derivative definition is consistent with the

    Riemann-Liouville positive non-integer order derivative definition.

    Summary

    Caputo's integral definition and Grunwald-Letnikov integral definition are consistent with the

    Riemann-Liouville integral definition. When p is positive integer and ),,2,1(0)()( pkaf k ,

    Caputo's derivative definition and Grunwald-Letnikov derivative definition are consistent with the

    Riemann-Liouville derivative definition. It implies that Grunwald-Letnikov positive non-integer order

    derivative definition is consistent with the Riemann-Liouville positive non-integer order derivative

    definition.

    556

  • Acknowledgements

    This research was supported by National Natural Science Foundation of China (Project No. 11161018,

    11561019) and Scientific Research Foundation of the Education Department of Guangxi Autonomous

    Region of China (No. 201106LX599).

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