Biquaternionic Description of the Schrödinger Equation

This paper begins with the introduction of biquaternion algebra and its properties in compact, profound and comprehensible approach. The Schrödinger equation including both the scalar Aharonov-Bohm(sAB) and Aharonov-Casher(AC) effects, that are currently popular in particle physics and condensed-matter physics, has been rewritten by biquaternions. The newly biquaternionic Schrödinger equation, which is defined with various assumptions and approaches, also includes the biquaternionic generalized momentum in Hamiltonian.


INTRODUCTION
In view of mathematicians, Dirac matrices are the generators of Clifford algebra.Quaternion [1,2] and Dirac algebras are considered as the special cases of Clifford algebra [3][4][5].Since a spinor with two elements is seen as an element of quaternion algebra, the Dirac spinor with four elements can also be considered as an element of Clifford algebra.Nowadays, the abstract Clifford algebras play a significant role in the investigation, quantization, improvement of supersymmetry concepts of particles with two valued spin such as fermions fitting the Pauli principle and quantum gravity [6].
In recent years, quaternions have been increasingly used in all fields.Accordingly to this, the quaternion algebra has been developing parallel to increasing usage fields of quaternions.These structures with applying of quaternions and octonions to exceptional groups and geometry have placed in physics.Complex quaternions (also named biquaternions) composed of an association of complex number and quaternion have been frequently used in general and special relativity, quantum mechanics, particle mechanics, acoustic and electromagnetism.Besides biquaternions belonging to Clifford algebra have a non-commutative algebraically structure in eight-dimensions, and matrix representations.These special features appear as an alternative way in the formulation of physical events [7][8][9][10][11][12].
It is a phenomenon that electromagnetic fields produce observable effects on quantum mechanical attitudes of moving particles, which exist out of the electromagnetic fields and its influence on non-commutative quantum mechanics is effective nearly in all fields in physics.The main problem here is how to define the biquaternionic generalized momentum in Hamiltonian.Actually, starting with Dirac equation [13][14][15][16][17][18] both sAB and AC effects have been investigated separately.After writing Dirac Lagrangian [19][20][21][22][23][24][25][26] and Hamiltonian [27][28][29][30][31] the above-mentioned Schrödinger equation can be expressed.In nonrelativistic limit, an effective Lagrangian can describe the interaction between charged particle and a magnetic moment.These effects are called as scalar Aharonov-Bohm (sAB) and Aharonov-Casher (AC) effects [19][20][21]32].Aharonov and Casher investigated a situation where electrically neutral particle exhibits a magnetic AB type effect in the presence of a fixed distribution of charge.
In the recent work, these effects have been investigated in an arbitrary direction of magnetic dipole [20].These effects have already been investigated in a noncommutative space.Mirza and Zarei [21] developed a novel method to study the topological phase of the AC effect while Chaichaian et al. [22] and Krey [23] described AB effect.The AC effect for quantum motion of a neutral magnetized particle in the electric field is believed to be a topological effect closely related to the known AB effect [21].
In this work, we propose to investigate with a new method for both sAB and AC effects.In this formulation, the Schrödinger equation governing the sAB and AC effects can be expressed in compact, simple and elegant approach with biquaternions.The organization of the paper is presented as follows: In section 2, biquaternion algebra and its properties are introduced.Biquaternionic forms of Hamiltonian and Schrödinger equation responsible for sAB and AC effects have been expressed in section 3. Finally, some suggestions and discussions have been given in the last section.

BIQUATERNION ALGEBRA
A biquaternion as an eight dimensional hypercomplex number can be defined as ] , , , ; , , , [ e e e e e e e e q q Q (1) where q and q are two quaternions and i is ordinary complex number ( 1 q q q q 3 2 1 0 , , , and all are real numbers., , e e e are the quaternion basis elements that obey the non-commutative multiplication rules as following equation: where jk  and jkl ε are the Kronecker delta and three-index Levi-Civita symbol respectively. Equation ( 1) can be written as Q are complex numbers.A biquaternion can be represented in terms of its scalar and vector parts as P   0 P P (4) where the scalar and vector parts of biquaternion, P , are 0 The product of two biquaternions as P and Q is where the dot and cross indicate the usual three-dimensional scalar and vector products respectively.The biquaternionic product is associative but not commutative.As in the familiar case of complex numbers, the biquaternionic conjugation is accomplished by changing the sign of the components of the imaginary basis elements, ] , , , ; , , , [ P and 0 Q are zero in eq.( 7), the products Q P. and Q P  can be transcribed by the following equations [10]: In general, the norm of a biquaternion Q is a complex number and is provided by however, the norm for biquaternions may be zero.Therefore, biquaternions do not form a division algebra.Biquaternions with unit norm are termed the unit biquaternions.The inverse of a biquaternion Q , whose norm is non-zero, is given by

BIQUATERNIONIC SCHRÖDINGER EQUATION FOR SAB AND AC EFFECTS
In this section, we aim to express the Schrödinger equation that contains sAB and AC effects in terms of biquaternions.
In former studies, there is a definition of Dirac Lagrangian with quaternions [25].The traditional form for the Dirac Lagrangian density is Also, as an alternative method, the novel Dirac equation and electron theory have been investigated by the above-mentioned algebras for different states and conditions, as mentioned in [7,9,10,18].Dirac equation, which obeys an electrically neutral spin half particle of rest mass m carrying a magnetic moment  and moving in an electromagnetic field, is where   is the Dirac matrices, ) , , (


and k  ' s are the usual Pauli matrices, E  and B  define the electric and the magnetic fields.The four spinor ψ can be expressed in terms of two-spinors  and  for the nonrelativistic limit [20]: The problem is to write the two-spinor equation as the biquaternionic Schrödinger equation in the nonrelativistic situation.
Using the vector identities, various assumptions and approaches, the Schrödinger equation governing the scalar Aharanov-Bohm and Aharanov-Casher effects has been suggested by Hyllus and Sjöqvist [20].If we think of an electrically neutral spin 2 1 particle of rest mass m carrying a magnetic moment mc e 2 /    and moving in an electromagnetic field, the two-spinor equation as the Schrödinger equation can be transcribed both vectors and matrices in different forms.
We introduce the biquaternionic generalized momentum П as: ] , , , the biquaternionic time operator, magnetic dipole and magnetic field, respectively The new biquaternionic Schrödinger equation responsible for the sAB and AC effects can be transcribed as the following equation: .On the right-hand side of eq.( 21), the first term is the biquaternionic Hamiltonian describing the interaction between a charged particle and a magnetic moment.At this stage, the sAB and the AC effects to arbitrary directions of the magnetic dipole have been extended with biquaternions.The non-commutative quantum mechanics can be defined with biquaternion by this equation.In the AB and sAB effects the conditions are given in terms of fields whereas in the AC and sAC effects the sources such as charges and currents take the role of fields.

CONCLUSIONS
The physics behind Aharonov-Bohm(AB) and Aharonov-Casher(AC) effects has been extensively discussed by using different methods and algebras.Although the quaternionic Dirac Lagrangian and biquaternionic Dirac equation have been expressed in different forms in literature.However, the formulations including sAB and AC effects have not been written by using biquaternionic algebra in literature before.For the first time, the biquaternionic Schrödinger equation (Eq.( 21)) governing the sAB and AC effects via biquaternionic Hamiltonian and biquaternionic generalized momentum (  ) has been derived and suggested.The Schrödinger equation has also been transcribed in eight dimensions (8D).The proposed method serves as a compact, useful, comprehensible and elegant formulations and it will also contribute to the existing studies in literature.By this formulation, the usage of different algebras together such as matrices, vectors, complex numbers in combined form is not needed.