Quantization of Fractional Singular Lagrangian Systems with Second-Order Derivatives Using Path Integral Method ()
1. Introduction
The quantization of singular Lagrangian systems has been studied with increasing interest and treated first by Dirac [1] [2], for quantizing physical systems. Following Dirac’s, researchers have developed a theory for investigating these systems using the canonical formalism [3]. The set of HJPDEs is constructed, and they wrote equations of motion as total differential equations. Then, the WKB approximation and path integral technique are quantized by using this formalism [4]-[8].
Fractional calculus with singular systems has been treated with more interest and importance [9]-[18]. Recently, the Euler-Lagrange formalism is analyzed for second-order Lagrangian systems within fractional calculus and the fractional Hamilton-Jacobi formalism for these systems is discussed [15] [16]. More recently, authors have constructed a formalism using the canonical method for quantizing singular systems for first-order derivatives [17] [18]. In this paper, we would like to extend our work for Lagrangians having second-order derivatives.
The most important definitions of fractional calculus [9] are:
1) The left Riemann-Liouville fractional derivative
. (1)
2) The right Riemann-Liouville fractional derivative
. (2)
where
is the Euler gamma function,
,
,
is an integer and these derivatives can be defined as follows:
,
, (3)
Definition: Given a function
. Then, for all
,
, let
. (4)
where
is called the conformal fractional derivative of
of order of
[17].
In this work, we aim to construct the formalism for quantizing singular Lagrangian systems with second-order derivatives in fractional form.
2. Fractional Path Integral Quantization and Fractional
Second-Order Singular Lagrangian
Following Hasan [19], we will use a formalism for second-order fractional singular Lagrangian systems to be applicable for quantizing these systems using the path integral approach. The Lagrangian formalism of second-order derivatives in fractional form is given by [19]:
. (5)
where
are the conformal fractional derivatives of the coordinates
[17].
The Lagrangian and Hamiltonian formalism for second-order derivatives have been studied by Ostrogradski [20] and these derivatives have been treated as coordinates. Therefore, we can treat these derivatives
and
as coordinates. Thus, the Poisson brackets can be defined as:
. (6)
where, the functions
and
are described in term of the canonical variables
,
,
and
. Thus, the generalized momenta
and
are conjugated to the generalized coordinates
and
respectively.
Now, the fractional of the Hessian matrix is defined as [19]:
,
(7)
The fractional Lagrangian is called regular if it’s rank is
otherwise the Lagrangian is singular
,
. Dirac showed in his formalism for investigating Lagrangians having singular nature that the number of degrees of freedom can be reduced from
to
due to the constraints [1] [2]. Thus, we can define the momenta
conjugated to the coordinates
as [19]:
,
(8)
,
. (9)
Also, the momenta
conjugated to the coordinates
can be defined as [19]:
; (10)
, (11)
where
(12)
and
(13)
Thus, Equations (12) and (13) represent primary constraints [1] [2] and can be written as:
; (14)
. (15)
We can calculate the Hamiltonian
in fractional form as:
(16)
A natural of singular Lagrangian indicates that the momenta
and
are not independent of
and
. Thus, we can write the set of fractional (HJPDEs) as:
; (17a)
; (17b)
. (17c)
where
is the fractional Hamilton’s principal function. Considering the definitions of the generalized momenta as
and
.
Researchers in Reference [5] wrote the equations of motion and Hamilton’s principal function as total differential equations, also we can write these equations in fractional form as follows [5]:
(18)
(19)
(20)
(21)
(22)
The set of Equations (18)-(22) are integrable if the total derivative of Equation (17) is zero [3] [5],
;
;
. (23)
Thus, the degrees of freedom are reduced from
to
, and the canonical phase space coordinates have been reduced from
to
. Therefore, the path integral approach can be represented in the fractional form as:
(24)
3. Example
We will discuss an example of second-order fractional singular Lagrangian has primary and secondary constraints:
(25)
The generalized momenta read:
; (26a)
; (26b)
; (26c)
; (26d)
; (26e)
. (26f)
Here, Equations (26c) and (26f) can be written as:
; (27)
. (28)
and represent as primary constraints [1] [2].
We calculate the fractional Hamiltonian
as:
(29)
The set of HJPDEs, are written as:
(30)
; (31)
. (32)
Using the fundamental Poisson brackets
and
,
, where
.
Thus,
. It gives secondary constraint [1] [2]:
. (33)
Following Dirac’s classification [1] [2], the constraint (32) is first-class and (31) and (33) are second-class. There are no further constraints.
The equations of motion (18)-(22) can be calculated as:
(34)
(35)
(36)
(37)
(38)
(39)
(40)
(41)
(42)
(43)
(44)
Considering
,
(45)
Integrate Equation (45), the action function becomes:
(46)
Finally, by obtaining the fractional action function
, we can represent the path integral approach in fractional form as:
(47)
Taking into account,
,
thus,
.
Thus, Equation (47) becomes:
(48)
4. Conclusion
In this work, we constructed a formalism for quantizing singular systems using fractional path integral technique. We wrote Hamilton’s principal function and equations of motion in fractional form as total differential equations. Calculating the fractional Hamilton’s principal function enabled us to formulate the fractional path integral technique. Then, the quantization can be carried out. Finally, we discussed a mathematical example to demonstrate our formalism.