Open Access
Issue
Wuhan Univ. J. Nat. Sci.
Volume 29, Number 6, December 2024
Page(s) 547 - 557
DOI https://doi.org/10.1051/wujns/2024296547
Published online 07 January 2025

© Wuhan University 2024

Licence Creative CommonsThis is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

0 Introduction

With the continuous development of mathematics and physics, fractional calculus has been widely discussed in recent years. Fractional-order model enables us to describe complex dynamics and physical behaviors better. Fractional calculus has important applications in fluid mechanics, nuclear magnetic resonance imaging, mechanics of complex viscoelastic materials, and so on[1-5]. Riewe[6,7] introduced fractional derivatives to deal with dissipative forces. After that, research on fractional derivatives has mainly focused on the left and right Riemann-Liouville, the left and right Caputo, the Riesz-Riemann-Liouville and the Riesz-Caputo fractional derivatives. Recently, a more general definition of fractional derivative, which is called combined fractional derivative, was introduced. For example, Malinowska and Torres[8] studied fractional calculus of variations based on a combined Caputo fractional derivative. Zhang[9] established the fractional differential equations of motion using a combined Riemann-Liouville fractional derivative. In 2015, Luo et al[10] presented the dynamics of a Birkhoffian system with both combined Caputo fractional derivatives and combined Riemann-Liouville fractional derivatives. Specifically, the four derivatives mentioned above are all special cases of the combined fractional derivative. Therefore, the combined fractional derivative is general.

The singular system refers to the procedure described by the singular Lagrangian. The singular system plays a vital role in modern quantum field theory, such as gravity theory, string (membrane) field theory, Yang-Mills theory, supersymmetry, and supergravity[11]. When a singular system is described by the canonical variables, there are several inherent constraints. In this case, the system is called the constrained Hamiltonian system, which is essential in condensed matter theory, gauge field theory and many other aspects[12-14].

Noether symmetry and Lie symmetry are two commonly used methods to study constrained mechanics systems. Noether symmetry was put forward by Noether[15]. Lie symmetry was introduced by Lutzky[16]. Then Noether and Lie symmetry were studied further[17,18]. Particularly, for singular systems, Lie symmetry and conserved quantity based on Riemann-Liouville fractional derivative[19], Noether symmetry and conserved quantity based on mixed order derivative and Caputo fractional derivative[20] are studied. Besides, based on the combined fractional derivative, Noether symmetry and conserved quantity for the Birkhoffian system are studied[21]. In this paper, we intend to study Noether symmetry and Lie symmetry for the singular system based on the combined fractional derivative.

Section 1 gives the preliminaries. In Section 2, the fractional Lagrange equation is analyzed using the combined fractional derivative. In Section 3 and Section 4, the fractional primary constraint is established and the Hamilton equation of the fractional constraint is given. In Section 5 and Section 6, the fractional Noether symmetry, Lie symmetry, and conserved quantities are studied, respectively. An example is given in Section 7 and the conclusion is given in Section 8.

1 Preliminaries

The following preliminaries are about the combined fractional derivatives, which can be seen in Ref. [8], Ref. [22] and Ref. [23]. The combined fractional derivative includes the combined Riemann-Liouville fractional derivative and the combined Caputo fractional derivative.

The combined Riemann-Liouville fractional derivative and combined Caputo fractional derivative are

R L D γ α , β f ( t ) = γ t 1 R L D t α f ( t ) + ( - 1 ) n ( 1 - γ ) t R L D t 2 β f ( t ) Mathematical equation(1)

C D γ α , β f ( t ) = γ t 1 C D t α f ( t ) + ( - 1 ) n ( 1 - γ ) t C D t 2 β f ( t ) Mathematical equation(2)

where t1RLDtαf(t)Mathematical equation, tRLDt2βf(t)Mathematical equation, t1CDtαf(t)Mathematical equation and tCDt2βf(t)Mathematical equation are the left and right Riemann-Liouville and Caputo fractional derivatives, t[t1,t2]Mathematical equation, 0γ1Mathematical equation, n-1α,β<nMathematical equation.

Under the condition 0<α,β<1Mathematical equation, we have

t 1 R L D t α f ( t ) = D t 1 C t α f ( t ) - 1 Γ ( 1 - α ) f ( t 1 ) ( t - t 1 ) α Mathematical equation(3)

t R L D t 2 β f ( t ) = D t C t 2 β f ( t ) + 1 Γ ( 1 - β ) f ( t 2 ) ( t 2 - t ) β Mathematical equation(4)

Additionally, the fractional partial integral formulae are

t 1 t 2 [ * ] D t 1 R L t α η d t = t 1 t 2 η D t C D t 2 α [ * ] d t - j = 0 n - 1 ( - 1 ) n + j D t 1 R L D t α + j - n η ( t ) D n - 1 - j [ * ] | t 1 t 2 Mathematical equation(5)

t 1 t 2 [ * ] D t R L t 2 β η d t = t 1 t 2 η D t 1 C D t β [ * ] d t - j = 0 n - 1 t R L D t 2 β + j - n η ( t ) D n - 1 - j [ * ] | t 1 t 2 Mathematical equation(6)

t 1 t 2 [ * ] D t 1 C t α η d t = t 1 t 2 η D t R L D t 2 α [ * ] d t + j = 0 n - 1 t R L D t 2 α + j - n [ * ] D n - 1 - j η ( t ) | t 1 t 2 Mathematical equation(7)

t 1 t 2 [ * ] D t 1 C t β η d t = t 1 t 2 η D t 1 R L D t β [ * ] d t + j = 0 n - 1 ( - 1 ) n + j D t 1 R L D t β + j - n [ * ] D n - 1 - j η ( t ) | t 1 t 2 Mathematical equation(8)

t 1 t 2 [ * ] D t 1 R t 2 α η d t = ( - 1 ) n t 1 t 2 η D t 1 R C D t 2 α [ * ] d t - j = 0 n - 1 ( - 1 ) n + j D t 1 R D t 2 α + j - n η ( t ) D n - 1 - j [ * ] | t 1 t 2 Mathematical equation(9)

t 1 t 2 [ * ] D t 1 R C t 2 α η d t = ( - 1 ) n t 1 t 2 η D t 1 R D t 2 α [ * ] d t + j = 0 n - 1 ( - 1 ) j D t 1 R D t 2 α + j - n [ * ] D n - 1 - j η ( t ) | t 1 t 2 Mathematical equation(10)

where D=d/dtMathematical equation represents the integer order derivative.

It should be noted that in this paper, we set 0<α,β<1Mathematical equation.

2 Fractional Lagrange Equation

In this section, the fractional variational problems under combined fractional derivatives are studied.

We give a function

I R L [ q R L ( ) ] = t 1 t 2 L R L ( t , q R L , D R L D γ α , β q R L ) d t ,   q R L ( t 1 ) = q R L 1 ,   q R L ( t 2 ) = q R L 2 , Mathematical equation(11)

where qRL=(qRL1,qRL2,,qRLn)Mathematical equation, RLγα,βqRL=(RLDγα,βqRL1,DRLDγα,βqRL2,,Mathematical equationRLDγα,βqRLn)Mathematical equation, qRL1=(qRL11,qRL12,,qRL1n)Mathematical equation, qRL2=(qRL21,qRL22,,qRL2n)Mathematical equation, and the Lagrangian LRLMathematical equation is assumed to be a C2Mathematical equation function. If qRL()Mathematical equation is an extremal of Eq. (11), we obtain

d d ε R L I R L [ q R L + ε R L h R L ] | ε R L = 0 = 0 , Mathematical equation(12)

where εRLMathematical equation is a small parameter, hRL=(hRL1,hRL2,,hRLn)Mathematical equation, hRL(t1)=hRL(t2)=0Mathematical equation. Further, we get

t 1 t 2 ( L R L q R L k h R L k + L R L D R L D γ α , β q R L k D R L D γ α , β h R L k ) d t = 0 ,   k = 1,2 , , n . Mathematical equation(13)

Using fractional partial integral formulae (Eqs. (5) and (6)) in the second terms of Eq. (13), we obtain

t 1 t 2 L R L D R L D γ α , β q R L k D R L D γ α , β h R L k d t = - t 1 t 2 ( h R L k D C D 1 - γ β , α L R L R L D γ α , β q R L k ) d t + γ Γ ( 1 - α ) t 1 t 2 ( t 2 - t ) - α h R L k d t L R L ( t 2 ) R L D γ α , β q R L k - 1 - γ Γ ( 1 - β ) t 1 t 2 ( t - t 1 ) - β h R L k   d t L R L ( t 1 ) R L D γ α , β q R L k Mathematical equation(14)

where LRL(t1)RLDγα,βqRLk=LRL(t1,qRL(t1),RLDγα,βqRL(t1))RLDγα,βqRLkMathematical equation, LRL(t2)RLDγα,βqRLk=LRLRLDγα,βqRLkMathematical equation(t2,qRL(t2),RLDγα,βqRL(t2))Mathematical equation. Substituting Eq. (14) into Eq. (13), we obtain

t 1 t 2 [ L R L q R L k - D C D 1 - γ β , α L R L R L D γ α , β q R L k + γ ( t 2 - t ) - α Γ ( 1 - α ) L R L ( t 2 ) R L D γ α , β q R L k - ( 1 - γ ) ( t - t 1 ) - β Γ ( 1 - β ) L R L ( t 1 ) R L D γ α , β q R L k ] h R L k d t = 0 . Mathematical equation(15)

According to the fundamental lemma of variational calculation[24], we can deduce that

L R L q R L k - D C 1 - γ β , α L R L R L D γ α , β q R L k + γ ( t 2 - t ) - α Γ ( 1 - α ) L R L ( t 2 ) R L D γ α , β q R L k - ( 1 - γ ) ( t - t 1 ) - β Γ ( 1 - β ) L R L ( t 1 ) R L D γ α , β q R L k = 0 , k = 1,2 , , n . Mathematical equation(16)

Eq. (16) is called the fractional Lagrange equation within the combined Riemann-Liouville fractional derivative.

The fractional Lagrange equation has another form, which can be obtained from Eqs. (3), (4), (7), (8) and (13) as

L R L q R L k - D R L 1 - γ β , α L R L D R L D γ α , β q R L k = 0 , k = 1,2 , n . Mathematical equation(17)

Similarly, the fractional Lagrange equation within the combined Caputo fractional derivative can also be obtained as

L C q C k - D R L 1 - γ β , α L C C D γ α , β q C k = 0 ,   k = 1,2 , , n , Mathematical equation(18)

where the Lagrangian LC=LC(t,qC,DCDγα,βqC)Mathematical equation, LCMathematical equation is assumed to be a C2Mathematical equation function,qC=(qC1,qC2,,qCn)Mathematical equation, Cγα,βqC=(CDγα,βqC1,DCDγα,βqC2,,DCDγα,βqCn)Mathematical equation.

Remark 1   Eqs. (16) and (18) are general and universal, so we can select different values of γMathematical equation to get different results.

3 Fractional Primary Constraint

This section presents fractional primary constraints within the combined Riemann-Liouville fractional derivative and combined Caputo fractional derivative.

Define fractional generalized momentum and Hamiltonian as

p R L k = L R L ( t , q R L , D R L D γ α , β q R L ) D R L D γ α , β q R L k , Mathematical equation(19)

H R L = p R L k D R L γ α , β q R L k - L R L ( t , q R L , D R L D γ α , β q R L ) ,   k = 1,2 , , n . Mathematical equation(20)

Here, we consider that the LRL(t,qRL,DRLDγα,βqRL)Mathematical equation is singular, meaning that only a portion of the terms RLγα,βqRLkMathematical equation, k=1,2,,nMathematical equation can be solved. In this case, we assume the number is RMathematical equation, 0R<nMathematical equation.

Firstly, when 1R<nMathematical equation, we have

R L D γ α , β q R L σ = f R L σ ( t , q R L , p R L E , D R L D γ α , β q R L ρ ) ,   σ , E = 1,2 , , R ,   ρ = R + 1 , , n , Mathematical equation(21)

where pRLE=(pRL1,pRL2,,pRLR)Mathematical equation, RLDγα,βqRLρ=(RLDγα,βqRL(R+1),RLDγα,βqRL(R+2),,Mathematical equationRLDγα,βqRLn)Mathematical equation, 1R<nMathematical equation. Substituting Eq. (21) into Eq. (19), we have

p R L k = g R L k ( t , q R L , f R L σ ( t , q R L , p R L E , D R L D γ α , β q R L ρ ) , D R L D γ α , β q R L ρ ) = g R L k ( t , q R L , p R L E , D R L D γ α , β q R L ρ ) , k = 1,2 , , n . Mathematical equation(22)

If k=1,2,,RMathematical equation, Eq. (22) obviously holds. If k=R+1,,nMathematical equation, we have

p R L ρ = g R L ρ ( t , q R L , p R L E )   o r   p R L F = g R L F ( t , q R L , p R L E ) ,   1 R < n , Mathematical equation(23)

where pRLF=(pRL(R+1),,pRLn)Mathematical equation, gRLF=(gRL(R+1),,gRLn)Mathematical equation, ρ=R+1,,nMathematical equation. Another form of Eq. (23) is

ϕ R L ( t , q R L , p R L ) = p R L F - g R L F ( t , q R L , p R L E ) = 0 , Mathematical equation(24)

where ϕRL=(ϕRL1,ϕRL2,,ϕRL(n-R))Mathematical equation, pRL=(pRL1,pRL2,,pRLn)Mathematical equation, 1R<nMathematical equation.

Secondly, when R=0Mathematical equation, RLγα,βqRLkMathematical equation cannot be solved. Therefore, from Eq. (19), we have

p R L k = g R L k ( t , q R L ) ,   k = 1,2 , , n . Mathematical equation(25)

ϕ R L a ( t , q R L , p R L ) = p R L a - g R L a ( t , q R L ) = 0 ,   a = 1,2 , , n . Mathematical equation(26)

From Eq. (24) and Eq. (26), we can obtain

ϕ R L a ( t , q R L , p R L ) = 0 ,   0 R < n ,   a = 1,2 , , n - R . Mathematical equation(27)

Eq. (27) is called fractional primary constraint within a combined Riemann-Liouville fractional derivative.

Similarly, we can define

p C k = L C ( t , q C , D C D γ α , β q C ) D C D γ α , β q C k ,   k = 1,2 , , n , Mathematical equation(28)

H C = p C k D C γ α , β q C k - L C ( t , q C , D C D γ α , β q C ) ,   k = 1,2 , , n . Mathematical equation(29)

The fractional primary constraint within the combined Caputo fractional derivative can be obtained as

ϕ C a ( t , q C , p C ) = 0 ,   0 R < n ,   a = 1,2 , , n - R ,   p C = ( p C 1 , p C 2 , , p C n ) . Mathematical equation(30)

Remark 2   According to the definition of the fractional generalized momenta (Eqs. (19) and (28)) rather than the fractional Euler-Lagrange equations (Eqs. (16) and (18)), the fractional primary constraints (Eqs. (27) and (30)) are obtained.

4 Fractional Constrained Hamilton Equation

Firstly, the fractional constrained Hamilton equation within the combined Riemann-Liouville fractional derivative is studied.

From Eq. (20), we obtain

δ H R L = δ p R L k D R L γ α , β q R L k - L R L q R L k δ q R L k ,   k = 1,2 , , n . Mathematical equation(31)

Besides, because of the Hamiltonian HRL=HRL(t,qRL,pRL)Mathematical equation, we have

δ H R L = H R L q R L k δ q R L k + H R L p R L k δ p R L k ,   k = 1,2 , , n . Mathematical equation(32)

It follows from Eqs. (31) and (32) that

( R L D γ α , β q R L k - H R L p R L k ) δ p R L k - ( L R L q R L k + H R L q R L k ) δ q R L k = 0 . Mathematical equation(33)

Making use of Eqs. (16) and (19), the term LRL/qRLkMathematical equation in Eq. (33) can be replaced by C1-γβ,αpRLk-γ(t2-t)-αΓ(1-α)pRLk(t2)+(1-γ)(t-t1)-βΓ(1-β)pRLk(t1)Mathematical equation, thus we have

( R L D γ α , β q R L k - H R L p R L k ) δ p R L k - [ C D 1 - γ β , α p R L k - γ ( t 2 - t ) - α Γ ( 1 - α ) p R L k ( t 2 ) + ( 1 - γ ) ( t - t 1 ) - β Γ ( 1 - β ) p R L k ( t 1 ) + H R L q R L k ] δ q R L k = 0 ,   k = 1,2 , , n , Mathematical equation(34)

where pRLk(t1)=LRL(t1)RLDγα,βqRLkMathematical equation, pRLk(t2)=LRL(t2)RLDγα,βqRLkMathematical equation. When the system (Eq. (16)) is singular, we have

λ R L a ϕ R L a q R L k δ q R L k + λ R L a ϕ R L a p R L k δ p R L k = 0 . Mathematical equation(35)

It follows from Eqs. (34) and (35) that

C 1 - γ β , a p R L k = - H R L q R L k + γ ( t 2 - t ) - α Γ ( 1 - α ) p R L k ( t 2 ) - ( 1 - γ ) ( t - t 1 ) - β Γ ( 1 - β ) p R L k ( t 1 ) - λ R L a ϕ R L a q R L k , Mathematical equation

R L γ α , β q R L k = H R L p R L k + λ R L a ϕ R L a p R L k ,   a = 1,2 , , n - R ,   0 R < n ,   k = 1,2 , , n . Mathematical equation(36)

Eq. (36) is called fractional constrained Hamilton equation within a combined Riemann-Liouville fractional derivative.

Similarly, we can also get the Hamilton equation with fractional constraints within the combined Caputo fractional derivative

R L 1 - γ α , β p C k = - H C q C k - λ C a ϕ C a q C k , D C γ α , β q C k = H C p C k + λ C a ϕ C a p C k ,   k = 1,2 , , n ,   a = 1,2 , , n - R ,   0 R < n . Mathematical equation(37)

Remark 3   Because of the various values of γMathematical equation, different results can be obtained from Eqs. (36) and (37).

According to the above method of establishing the Hamilton equation with fractional constraints, it is very important to solve the Lagrange multiplier. Next, we will calculate the Lagrange multiplier by fractional Poisson bracket.

Let F=F(t,q,p)Mathematical equation, G=G(t,q,p)Mathematical equation, q=(q1,q2,,qn)Mathematical equation, p=(p1,p2,,pn)Mathematical equation, then we define

{ F , G } = F q k G p k - F p k G q k ,   k = 1,2 , , n . Mathematical equation(38)

Then we have

( { ϕ R L a , H R L } + λ R L b { ϕ R L a , ϕ R L b } ) ϕ R L a q R L j q ˙ R L j + ( ϕ R L a t + ϕ R L a p R L j p ˙ R L j ) × ϕ R L a q R L k D R L γ α , β q R L k - ( ϕ R L a p R L k ϕ R L a q R L j q ˙ R L j ) [ C D 1 - γ β , α p R L k - γ ( t 2 - t ) - α Γ ( 1 - α ) p R L k ( t 2 ) + ( 1 - γ ) ( t - t 1 ) - β Γ ( 1 - β ) p R L k ( t 1 ) ] = 0 , a , b = 1,2 , , n - R ,   k , j = 1,2 , , n ,   0 R < n , Mathematical equation(39)

and

( { ϕ C a , H C } + λ C b { ϕ C a , ϕ C b } ) ϕ C a q C j q ˙ C j + ( ϕ C a t + ϕ C a p C j p ˙ C j ) × ϕ C a q C k D C γ α , β q C k - ϕ C a p C k ϕ C a q C j q ˙ C j D R L 1 - γ β , α p C k = 0 , a , b = 1,2 , , n - R ,   k , j = 1,2 , , n ,   0 R < n . Mathematical equation(40)

From Eqs. (39) and (40), the Lagrange multipliers can be calculated.

5 Noether Theorem

Definition 1   A quantity CMathematical equation is called a conserved quantity if and only if dC/dt=0Mathematical equation.

5.1 Noether Theorem within the Combined Riemann-Liouville Fractional Derivative

The Hamilton action within the combined Riemann-Liouville fractional derivative is

I R L = t 1 t 2 [ p R L k D R L D γ α , β q R L k - H R L ( t , q R L , p R L ) ] d t . Mathematical equation(41)

The infinitesimal transformations are

t ¯ = t + Δ t ,   q ¯ R L k ( t ¯ ) = q R L k ( t ) + Δ q R L k ,    p ¯ R L k ( t ¯ ) = p R L k ( t ) + Δ p R L k ,   k = 1,2 , , n . Mathematical equation(42)

Namely,

t ¯ = t + θ R L ξ R L 0 ( t , q R L , p R L ) + o ( θ R L ) ,   q ¯ R L k ( t ¯ ) = q R L k ( t ) + θ R L ξ R L k ( t , q R L , p R L ) + o ( θ R L ) , p ¯ R L k ( t ¯ ) = p R L k ( t ) + θ R L η R L k ( t , q R L , p R L ) + o ( θ R L ) , Mathematical equation(43)

where θRLMathematical equation is a small parameter, ξRL0Mathematical equation, ξRLkMathematical equation, and ηRLkMathematical equation are infinitesimal generators, and o(θRL)Mathematical equation means the higher order of θRLMathematical equation.

Letting ΔIRLMathematical equation be the linear part of I¯RL-IRLMathematical equation, and without considering the higher order of θRLMathematical equation, we obtain

Δ I R L = θ R L t 1 t 2 [ p R L k D R L D γ α , β ( ξ R L k - q ˙ R L k ξ R L 0 ) + ( p R L k D R L D γ α , β q R L k - H R L ) ξ ˙ R L 0 + ( p R L k d d t D R L D γ α , β q R L k - H R L t ) ξ R L 0 - H R L q R L k ξ R L k + λ R L a ϕ R L a p R L k η R L k + q R L k ( t 2 ) ξ R L 0 ( t 2 ) × ( 1 - γ ) p R L k Γ ( 1 - β ) d d t ( t 2 - t ) - β - q R L k ( t 1 ) ξ R L 0 ( t 1 ) γ p R L k Γ ( 1 - α ) d d t ( t - t 1 ) - α ] d t Mathematical equation(44)

where ξRL0(t1)=ξRL0(t1,qRL(t1),pRL(t1))Mathematical equation and ξRL0(t2)=ξRL0(t2,qRL(t2),pRL(t2))Mathematical equation. Let ΔIRL=0Mathematical equation, then Eq. (44) gives

p R L k R L D γ α , β ( ξ R L k - q ˙ R L k ξ R L 0 ) + ( p R L k D R L D γ α , β q R L k - H R L ) ξ ˙ R L 0 + λ R L a ϕ R L a p R L k η R L k + ( p R L k d d t D R L D γ α , β q R L k - H R L t ) ξ R L 0 - H R L q R L k ξ R L k + q R L k ( t 2 ) ξ R L 0 ( t 2 ) × ( 1 - γ ) p R L k Γ ( 1 - β ) d d t ( t 2 - t ) - β - q R L k ( t 1 ) ξ R L 0 ( t 1 ) γ p R L k Γ ( 1 - α ) d d t ( t - t 1 ) - α = 0 Mathematical equation(45)

Equation (45) is called the fractional Noether identity within the combined Riemann-Liouville fractional derivative.

Theorem 1   If ξRL0Mathematical equation, ξRLkMathematical equation, and ηRLkMathematical equation satisfy Eq. (45), then there exists a conserved quantity

C R L = ( p R L k D R L D γ α , β q R L k - H R L ) ξ R L 0 + t 1 t { p R L k D R L D γ α , β ( ξ R L k - q ˙ R L k ξ R L 0 ) + ( ξ R L k - q ˙ R L k ξ R L 0 ) [ C D 1 - γ β , α p R L k - γ ( t 2 - τ ) - α Γ ( 1 - α ) p R L k ( t 2 ) + ( 1 - γ ) ( τ - t 1 ) - β Γ ( 1 - β ) p R L k ( t 1 ) ] } d τ + q R L k ( t 2 ) ξ R L 0 ( t 2 ) 1 - γ Γ ( 1 - β ) t 1 t p R L k d d τ ( t 2 - τ ) - β d τ - q R L k ( t 1 ) ξ R L 0 ( t 1 ) γ Γ ( 1 - α ) t 1 t p R L k d d τ ( τ - t 1 ) - α d τ Mathematical equation(46)

for the system within the combined Riemann-Liouville fractional derivative.

Proof   Using Eqs. (27), (36), and (45), we have

d C R L d t = ( p R L k D R L D γ α , β q R L k - H R L ) ξ ˙ R L 0 + ξ R L 0 ( p ˙ R L k D R L D γ α , β q R L k + p R L k d d t D R L D γ α , β q R L k - H R L t - H R L q R L k q ˙ R L k - H R L p R L k p ˙ R L k ) Mathematical equation

+ p R L k R L D γ α , β ( ξ R L k - q ˙ R L k ξ R L 0 ) + ( ξ R L k - q ˙ R L k ξ R L 0 ) [ C D 1 - γ β , α p R L k - γ ( t 2 - t ) - α Γ ( 1 - α ) p R L k ( t 2 ) + ( 1 - γ ) ( t - t 1 ) - β Γ ( 1 - β ) p R L k ( t 1 ) ] Mathematical equation

+ q R L k ( t 2 ) ξ R L 0 ( t 2 ) 1 - γ Γ ( 1 - β ) p R L k d d t ( t 2 - t ) - β - q R L k ( t 1 ) ξ R L 0 ( t 1 ) γ Γ ( 1 - α ) p R L k d d t ( t - t 1 ) - α Mathematical equation

= H R L q R L k ξ R L k - λ R L a ϕ R L a p R L k η R L k + ξ R L 0 ( p ˙ R L k λ R L a ϕ R L a p R L k - H R L q R L k q ˙ R L k ) + ( ξ R L k - q ˙ R L k ξ R L 0 ) ( - H R L q R L k - λ R L a ϕ R L a q R L k ) = - λ R L a ϕ R L a p R L k ( η R L k - p ˙ R L k ξ R L 0 ) - λ R L a ϕ R L a q R L k ( ξ R L k - q ˙ R L k ξ R L 0 ) = - λ R L a δ ϕ R L a = 0 . Mathematical equation

The proof is completed.

5.2 Noether Theorem within the Combined Caputo Fractional Derivative

The Hamilton action within the combined Caputo fractional derivative is

I C = t 1 t 2 [ p C k D C D γ α , β q C k - H C ( t , q C , p C ) ] d t . Mathematical equation(47)

The infinitesimal transformations are

t ¯ = t + Δ t ,   q ¯ C k ( t ¯ ) = q C k ( t ) + Δ q C k , p ¯ C k ( t ¯ ) = p C k ( t ) + Δ p C k ,   k = 1,2 , , n . Mathematical equation(48)

Namely,

t ¯ = t + θ C ξ C 0 ( t , q C , p C ) + o ( θ C ) ,   q ¯ C k ( t ¯ ) = q C k ( t ) + θ C ξ C k ( t , q C , p C ) + o ( θ C ) ,   p ¯ C k ( t ¯ ) = p C k ( t ) + θ C η C k ( t , q C , p C ) + o ( θ C ) Mathematical equation(49)

where θCMathematical equation is a small parameter, ξC0Mathematical equation, ξCkMathematical equation, and ηCkMathematical equation are infinitesimal generators. Letting ΔIC=I¯C-IC=0Mathematical equation, we have

p C k D C γ α , β ( ξ C k - q ˙ C k ξ C 0 ) + ( p C k D C D γ α , β q C k - H C ) ξ ˙ C 0 + ( p C k d d t D C D γ α , β q C k - H C t ) ξ C 0 - H C q C k ξ C k + λ C a ϕ C a p C k η C k + q ˙ C k ( t 2 ) ξ C 0 ( t 2 ) ( 1 - γ ) p C k Γ ( 1 - β ) ( t 2 - t ) - β - q ˙ C k ( t 1 ) ξ C 0 ( t 1 ) γ p C k Γ ( 1 - α ) ( t - t 1 ) - α = 0 Mathematical equation(50)

Equation (50) is called fractional Noether identity within a combined Caputo fractional derivative.

Theorem 2   If ξC0Mathematical equation, ξCkMathematical equation, and ηCkMathematical equation satisfy Eq. (50), then there exists a conserved quantity

C C = ( p C k D C D γ α , β q C k - H C ) ξ C 0 + t 1 t [ p C k D C D γ α , β ( ξ C k - q C k ξ C 0 ) + ( ξ C k - q ˙ C k ξ C 0 ) D R L D 1 - γ β , α p C k ] d τ + q ˙ C k ( t 2 ) ξ C 0 ( t 2 ) 1 - γ Γ ( 1 - β ) t 1 t p C k ( t 2 - τ ) - β d τ - q ˙ C k ( t 1 ) ξ C 0 ( t 1 ) γ Γ ( 1 - α ) t 1 t p C k ( τ - t 1 ) - α d τ Mathematical equation(51)

for the system within a combined Caputo fractional derivative.

Proof   Using Eqs. (30), (37), and (50), it is easy to obtain

d C C d t = ( p C k D C D γ α , β q C k - H C ) ξ ˙ C 0 + ξ C 0 ( p ˙ C k D C D γ α , β q C k + p C k d d t D C D γ α , β q C k - H C t - H C q C k q ˙ C k - H C p C k p ˙ C k ) + p C k D C γ α , β ( ξ C k - q ˙ C k ξ C 0 ) + ( ξ C k - q ˙ C k ξ C 0 ) D R L 1 - γ β , α p C k + q ˙ C k ( t 2 ) ξ C 0 ( t 2 ) ( 1 - γ ) p C k Γ ( 1 - β ) ( t 2 - t ) - β - q ˙ C k ( t 1 ) ξ C 0 ( t 1 ) γ p C k Γ ( 1 - α ) ( t - t 1 ) - α + q ˙ C k ( t 2 ) ξ C 0 ( t 2 ) ( 1 - γ ) p C k Γ ( 1 - β ) ( t 2 - t ) - β - q ˙ C k ( t 1 ) ξ C 0 ( t 1 ) γ p C k Γ ( 1 - α ) ( t - t 1 ) - α = H C q C k ξ C k - λ C a ϕ C a p C k η C k + ξ C 0 ( p ˙ C k λ C a ϕ C a p C k - H C q C k q ˙ C k ) - ( ξ C k - q C k ξ C 0 ) ( H C q C k + λ C a ϕ C a q C k ) = - λ C a ϕ C a p C k ( η C k - ξ C 0 p ˙ C k ) - λ C a ϕ C a q C k ( ξ C k - q ˙ C k ξ C 0 ) = - λ C a δ ϕ C a = 0 Mathematical equation

The proof is completed.

6 Lie Symmetry Conserved Quantity

6.1 Lie Symmetry Conserved Quantity within the Combined Riemann-Liouville Fractional Derivative

Eq. (36) can be expressed as

R L D γ α , β q R L k = h R L k ( t , q R L , p R L ) ,   k = 1,2 , , n , Mathematical equation(52)

C 1 - γ β , α p R L k = f R L k ( t , q R L , p R L ) ,   k = 1,2 , , n . Mathematical equation(53)

We then study Eqs. (52) and (53) under the infinitesimal transformations (Eq. (43)). For Eq. (52), we obtain

R L D γ ¯ α , β q ¯ R L k - h R L k ( t ¯ , q ¯ R L k , p ¯ R L k ) = D R L γ α , β q R L k - h R L k ( t , q R L , p R L ) + θ R L [ R L D γ α , β ( ξ R L k - q ˙ R L k ξ R L 0 ) + ξ R L 0 d d t D R L D γ α , β q R L k - X R L ( 0 ) ( h R L k ) - q R L k ( t 1 ) γ ξ R L 0 ( t 1 ) Γ ( 1 - α ) d d t ( t - t 1 ) - α + q R L k ( t 2 ) ξ R L 0 ( t 2 ) 1 - γ Γ ( 1 - β ) d d t ( t 2 - t ) - β ] Mathematical equation(54)

where XRL(0)=ξRL0t+ξRLiqRLi+ηRLipRLi, i=1,2,,n. For Eq. (53), we haveMathematical equation

C 1 - γ β , α p ¯ R L k = f R L k ( t ¯ , q ¯ R L , p ¯ R L ) = D C 1 - γ β , α p R L k - f R L k ( t , q R L , p R L ) + θ R L [ C D 1 - γ β , α ( η R L k - p ˙ R L k ξ R L 0 ) + ξ R L 0 d d t D C D 1 - γ β , α p R L k - X R L ( 0 ) ( f R L k ) - 1 - γ Γ ( 1 - β ) ( t - t 1 ) - β p ˙ R L k ( t 1 ) ξ R L 0 ( t 1 ) + γ Γ ( 1 - α ) ( t 2 - t ) - α p ˙ R L k ( t 2 ) ξ R L 0 ( t 2 ) ] Mathematical equation(55)

The fractional primary constraint (Eq. (27)) gives

ϕ R L a ( t , q ¯ R L , p ¯ R L ) = ϕ R L a ( t , q R L , p R L ) + θ R L X R L ( 0 ) ( ϕ R L a ) . Mathematical equation(56)

Therefore, we have

R L D γ α , β ( ξ R L k - q ˙ R L k ξ R L 0 ) + ξ R L 0 d d t D R L γ α , β q R L k - X R L ( 0 ) ( h R L k ) - q R L k ( t 1 ) γ ξ R L 0 ( t 1 ) Γ ( 1 - α ) d d t ( t - t 1 ) - α + q R L k ( t 2 ) ξ R L 0 ( t 2 ) 1 - γ Γ ( 1 - β ) d d t ( t 2 - t ) - β = 0 , Mathematical equation(57)

C 1 - γ β , α ( η R L k - p ˙ R L k ξ R L 0 ) + ξ R L 0 d d t D C 1 - γ β , α p R L k - X R L ( 0 ) ( f R L k ) - 1 - γ Γ ( 1 - β ) ( t - t 1 ) - β p ˙ R L k ( t 1 ) ξ R L 0 ( t 1 ) + γ Γ ( 1 - α ) ( t 2 - t ) - α p ˙ R L k ( t 2 ) ξ R L 0 ( t 2 ) = 0 , Mathematical equation(58)

and

X R L ( 0 ) ( ϕ R L a ) = 0 . Mathematical equation(59)

Equations (57) and (58) are called the determined equations within the combined Riemann-Liouville fractional derivative, and Eq. (59) is called the limited equation within the combined Riemann-Liouville fractional derivative.

Besides, if we consider the deduction process of the system (Eq. (36)), an extra additional limited equation

ϕ R L a q R L i ( ξ R L i - q ˙ R L i ξ R L 0 ) + ϕ R L a p R L i ( η R L i - p ˙ R L i ξ R L 0 ) = 0 Mathematical equation(60)

can be obtained. Then we have

Theorem 3   For the system within the combined Riemann-Liouville fractional derivative (Eq. (36)), when Eqs. (45), (57) and (58) are satisfied, Eq. (46) gives a Lie symmetry conserved quantity; when Eqs. (45), (57)-(59) are satisfied, Eq. (46) gives a weak Lie symmetry conserved quantity; when Eqs. (45), (57)-(60) are satisfied, Eq. (46) gives a strong Lie symmetry conserved quantity.

6.2 Lie Symmetry Conserved Quantity within the Combined Caputo Fractional Derivative

Eq. (37) can be expressed as

C γ α , β q C k = h C k ( t , q C , p C ) ,   k = 1,2 , , n , Mathematical equation(61)

R L 1 - γ β , α p C k = f C k ( t , q C , p C ) ,   k = 1,2 , , n . Mathematical equation(62)

Using the similar way, we can obtain the determined equations within the combined Caputo fractional derivative

C D γ α , β ( ξ C k - q ˙ C k ξ C 0 ) + ξ C 0 d d t D C γ α , β q C k - X C ( 0 ) ( h C k ) - q ˙ C k ( t 1 ) γ ξ C 0 ( t 1 ) Γ ( 1 - α ) ( t - t 1 ) - α + q ˙ C k ( t 2 ) ξ C 0 ( t 2 ) 1 - γ Γ ( 1 - β ) ( t 2 - t ) - β = 0 , Mathematical equation(63)

R L 1 - γ β , α ( η C k - p ˙ C k ξ C 0 ) + ξ C 0 d d t D R L 1 - γ β , α p C k - X C ( 0 ) - 1 - γ Γ ( 1 - β ) p C k ( t 1 ) ξ C 0 ( t 1 ) d d t ( t - t 1 ) - β + γ Γ ( 1 - α ) p C k ( t 2 ) ξ C 0 ( t 2 ) d d t ( t 2 - t ) - α = 0 , Mathematical equation(64)

the limited equation within the combined Caputo fractional derivative

X C ( 0 ) ( ϕ C a ) = 0 , Mathematical equation(65)

and the additional limited equation within the combined Caputo fractional derivative

ϕ C a q C i ( ξ C i - q ˙ C i ξ C 0 ) + ϕ C a p C i ( η C i - p ˙ C i ξ C 0 ) = 0 , Mathematical equation(66)

where XC(0)=ξC0t+ξCiqCi+ηCipCi, i=1,2,,nMathematical equation. Then we have

Theorem 4   For the system within the combined Caputo fractional derivative (Eq. (37)), when Eqs. (50), (63) and (64) are satisfied, Eq. (51) gives a Lie symmetry conserved quantity; when Eqs. (50), (63)-(65) are satisfied, Eq. (51) gives a weak Lie symmetry conserved quantity; when Eqs. (50), (63)-(66) are satisfied, Eq. (51) gives a strong Lie symmetry conserved quantity.

7 An Example

The singular Lagrangian is

L R L = - c 2 ( q R L 1 ) 2 + b 2 ( q R L 2 ) 2 + 1 2 ( q R L 2 R L D γ α , β q R L 1 - q R L 1 R L D γ α , β q R L 2 ) . Mathematical equation(67)

Try to study its Noether symmetry and conserved quantity.

From Eqs. (19) and (20), we can obtain

p R L 1 = L R L R L D γ α , β q R L 1 = 1 2 q R L 2 ,   p R L 2 = L R L R L D γ α , β q R L 2 = - 1 2 q R L 1 , Mathematical equation(68)

H R L = p R L 1 R L D γ α , β q R L 1 + p R L 2 R L D γ α , β q R L 2 - L R L = c 2 ( q R L 1 ) 2 - b 2 ( q R L 2 ) 2 . Mathematical equation(69)

Then Eq. (27) gives two fractional primary constraints

ϕ R L 1 = p R L 1 - 1 2 q R L 2 = 0 ,   ϕ R L 2 = p R L 2 + 1 2 q R L 1 = 0 . Mathematical equation(70)

From Eq. (39), we obtain

b q ˙ R L 1 q R L 2 + λ R L 1 q ˙ R L 1 + p ˙ R L 2 R L D γ α , β q R L 1 - q ˙ R L 1 [ C D 1 - γ β , α p R L 2 - ( t 2 - t ) - α Γ ( 1 - α ) p R L 2 ( t 2 ) + ( 1 - γ ) ( t - t 1 ) - β Γ ( 1 - β ) p R L 2 ( t 1 ) ] = 0 , Mathematical equation(71)

c q R L 1 q ˙ R L 2 + λ R L 2 q ˙ R L 2 - p ˙ R L 1 R L D γ α , β q R L 2 + q ˙ R L 2 [ C D 1 - γ β , α p R L 1 - γ ( t 2 - t ) - α Γ ( 1 - α ) p R L 1 ( t 2 ) + ( 1 - γ ) ( t - t 1 ) - β Γ ( 1 - β ) p R L 1 ( t 1 ) ] = 0 . Mathematical equation(72)

Then, using Eq. (36), the fractional constrained Hamilton equation within the combined Riemann-Liouville fractional derivative is

R L D γ α , β q R L 1 = - 2 b q R L 2 + 2 [ C D 1 - γ β , α p R L 2 - γ ( t 2 - t ) - α Γ ( 1 - α ) p R L 2 ( t 2 ) + ( 1 - γ ) ( t - t 1 ) - β Γ ( 1 - β ) p R L 2 ( t 1 ) ] , Mathematical equation

R L D γ α , β q R L 2 = - 2 c q R L 1 - 2 [ C D 1 - γ β , α p R L 1 - γ ( t 2 - t ) - α Γ ( 1 - α ) p R L 1 ( t 2 ) + ( 1 - γ ) ( t - t 1 ) - β Γ ( 1 - β ) p R L 1 ( t 1 ) ] . Mathematical equation(73)

From Noether identity (Eq. (45)), we have

p R L 1 D R L γ α , β ( ξ R L 1 - q ˙ R L 1 ξ R L 0 ) + p R L 2 R L D γ α , β ( ξ R L 2 - q ˙ R L 2 ξ R L 0 ) - c q R L 1 ξ R L 1 + b q R L 2 ξ R L 2 + ( p R L 1 d d t D R L D γ α , β q R L 1 + p R L 2 d d t D R L D γ α , β q R L 2 ) ξ R L 0 + λ R L 1 η R L 1 + λ R L 2 η R L 2 + ( p R L 1 R L D γ α , β q R L 1 + p R L 2 R L D γ α , β q R L 2 - H R L ) ξ ˙ R L 0 + q R L 1 ( t 2 ) ξ R L 0 ( t 2 ) × ( 1 - γ ) p R L 1 Γ ( 1 - β ) d d t ( t 2 - t ) - β - q R L 1 ( t 1 ) ξ R L 0 ( t 1 ) γ p R L 1 Γ ( 1 - α ) d d t ( t - t 1 ) - α + q R L 2 ( t 2 ) ξ R L 0 ( t 2 ) × ( 1 - γ ) p R L 2 Γ ( 1 - β ) d d t ( t 2 - t ) - β - q R L 2 ( t 1 ) ξ R L 0 ( t 1 ) γ p R L 2 Γ ( 1 - α ) d d t ( t - t 1 ) - α = 0 Mathematical equation(74)

Then we can verify that

ξ R L 0 = - 1 ,   ξ R L 1 = ξ R L 2 = 0 ,   η R L 1 = η R L 2 = 0 Mathematical equation(75)

satisfy Eq. (74). Therefore, we have

C R L = - ( p R L 1 R L D γ α , β q R L 1 + p R L 2 R L D γ α , β q R L 2 - c 2 q R L 1 2 + b 2 q R L 2 2 ) + t 1 t { p R L 1 d d τ D R L D γ α , β q R L 1 + p R L 2 d d τ D R L D γ α , β q R L 2 + q ˙ R L 1 [ C D 1 - γ β , α p R L 1 - γ ( t 2 - τ ) - α Γ ( 1 - α ) p R L 1 ( t 2 ) + ( 1 - γ ) ( τ - t 1 ) - β Γ ( 1 - β ) p R L 1 ( t 1 ) ] + q ˙ R L 2 [ C D 1 - γ β , α p R L 2 - γ ( t 2 - τ ) - α Γ ( 1 - α ) p R L 2 ( t 2 ) + ( 1 - γ ) ( τ - t 1 ) - β Γ ( 1 - β ) p R L 2 ( t 1 ) ] } d τ Mathematical equation(76)

Specially, we degenerate the above fractional order to the integer order, namely α,β1Mathematical equation, so we can get

C R L 0 = - c 2 q R L 1 2 + b 2 q R L 2 2 . Mathematical equation(77)

If t[1,10]Mathematical equation, and let b=c=1,qRL1(1)=0,qRL2(1)=1,Mathematical equation the trajectory of CRL0Mathematical equation can be drawn as follows.

It follows from Fig. 1 that CRL0Mathematical equation is a constant.

Thumbnail: Fig. 1 Refer to the following caption and surrounding text. Fig. 1 The trajectory of CRL0Mathematical equation

8 Conclusion

Fractional calculus has important applications in various fields, and it is also a research hotspot. In this paper, based on the combined Riemann-Liouville fractional derivative and combined Caputo fractional derivative, we establish Noether theorem and Lie theorem for the fractional constrained Hamiltonian system. Besides, Noether identity, determined equation, limited equation and additional limited equation are presented.

In this paper, Noether-type conserved quantity is obtained from Lie symmetry, whether the Lie symmetry of the system can lead to another conserved quantity, called Hojman conserved quantity, remains to be studied. At the same time, Mei symmetry is also an effective method to solve the differential equation. Therefore, Mei symmetry is also a future research direction.

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All Figures

Thumbnail: Fig. 1 Refer to the following caption and surrounding text. Fig. 1 The trajectory of CRL0Mathematical equation
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