1. Introduction
Any attempt to measure precisely the velocity of a subatomic particle, such as an electron, which is unpredictable, means that the simultaneous measurement of its position has no validity. This is the result of the principle of quantum mechanics (QM), formulated by Heisenberg [
1], that accurate measurement of the one of two related observable quantities, as position and momentum or energy and time, produces uncertainties in the measurement of the other one, such that the product of the uncertainties of both quantities is equal to or greater than ℏ/2
π, where ℏ is the Planck’s constant. Heisenberg's uncertainty principle is often expressed as the limitation of operational possibilities imposed by QMs. The Heisenberg’s uncertainty principle (HUP) has been extended to contain the existence of a minimal uncertainty in momentum. Therefore, we have another modified form of Heisenberg uncertainty principle in an (anti)-de Sitter background in which the Heisenberg uncertainty principle should be modified by introducing some corrections proportional to the cosmological constant with the (anti)-de Sitter radius. The de Sitter space was introduced by Willem de Sitter [
2]. In the de Sitter background, space has a positive radius and in the anti-de Sitter background it has a negative radius. The modified form of the Heisenberg relations in both spaces is referred to as extended uncertainty principle (EUP). Then, we know that EUP has a minimal uncertainty in the momentum. The HUP should break down at energies near to Planck scale [
1], and produce a sentence of Planck scale, that is a modified Heisenberg uncertainty relation and leads to deformed canonical commutator due to generalized uncertainty principle (GUP). On the other hand, GUP predicts the existence of a minimal length. Some approaches in physics predict this minimal length, Gedanken experiment [
3], String theory [
4–
6], and black hole [
7]. In the String theory, a GUP approach was introduced by Amati and
et al [
8]. This approach leads to finding a distance smaller than characteristic string length [
4–
6,
9]. Kempf introduced a minimal length scale to the mathematical basis of QM [
10–
13]. Thus, QM and quantum gravity are in agreement for the existence of a minimal uncertainty in position. These results are consistent with the non-commutative space–time discussed in [
12,
14,
15] in the Minkowski spacetime.
In this paper we investigate the Heisenberg algebra using momentum representation by modified (anti)-Snyder based on GUP. In the second section, we introduce different modified anti-de Sitter and de Sitter models. In section 3, we obtain the different representations in the position space and the momentum space for the introduced commutation relations. Then, we obtain eigenstates of momentum in the position space in section 4. In section 5, we assume a new algebraic approach for these commutation relations and obtain the wave function in the momentum representation, and we calculate the Heisenberg algebra for a free particle in the modified anti-de Sitter and de Sitter models in section 6. We calculate the Heisenberg algebra by solving through the successive approximation method with Hamiltonian by considering harmonic oscillator potential for all commutation relations. In section 7, we introduce the GUP in Snyder and anti-Snyder space and obtain the modified kinetic energies, velocities and coordinates from the Poisson bracket in Snyder background and we obtain the modified frequency from solving Heisenberg algebra by considering Hamiltonian with Harmonic oscillator potential in the momentum representation for GUP in the Snyder and anti-Snyder space.
2. General extension of the (anti)-de Sitter model
We have another modified relation of the HUP [
1] in an (anti)-de Sitter background. The HUP should be modified by introducing some corrections proportional to the cosmological constant , , with
LH the (anti)-de Sitter radius and [
10,
16]. Also we know de Sitter’s space–time is an exact solution of the equations of ordinary general relativity discovered in 1917 [
2]. Also it can be defined as a sub manifold of a generalized Minkowski space of one higher dimension. In quantum field theory based on a curved space, the anti-de Sitter space–time (Ads) is a maximally symmetric with a negative cosmology constant (negative radius with
LH > 0) and the cosmology constant is positive in the de Sitter space–time. In the case of zero curvature of this space–time, we have Minkowski space. As such, they are exact solutions of Einstein’s field equations for an empty universe with a positive, zero or negative cosmological constants, respectively. This space–time was named after Willem de Sitter [
17]. Modified Heisenberg equation under the EUP in the de Sitter space is represented as [
18]
Also, in the anti-de Sitter space for EUP we have [
19,
20]
In this representation for EUP in the de Sitter and anti-de Sitter we have
This representation leads to
The relation between the EUP position and the canonical position in anti-de Sitter model is obtained as
Then, we have the modified position and its ordinary form as
in which
X and
x represent the modified position and its ordinary form, respectively. We can find the limits from above equations as
The EUP in the de Sitter background can be generalized into the following form [
21]
where
a = 1 gives the ordinary EUP model. The relation between the EUP position and canonical position is
Then, we can write the extended following relations for EUP
Now, we obtain another different representation for EUP
where
From the self-adjointness of the operator
P we have the following inner product
And the expectation value of the operator
where
φ(
X) obey
and the normalization condition
first we will incorporate that
which implies that cannot be zero for all normalized wave functions
φ(
X). Let us assume that
L = 0. Then we have
Because , we have
φ(
X) = 0 for all . Then, we have
That contradicts equation (
18). Therefore and 0 <
L < 1. Because for all we get
Thus, we have
Therefore, it has been shown that the modified (anti)-de Sitter model (
13) has the non-zero minimal momentum.
3. Three representations of the modified (anti)-de Sitter model
For the modified anti-de Sitter and de Sitter model we have three types of representations.
3.1. EUP position representation
The EUP position representation for algebra (
13) is as [
22]
The EUP position representation acts on the square integrable functions
and the norm of
ψ(
X) is given by
The Schrödinger equation reads
3.2. EUP momentum representation
The momentum representation for the EUP (
13)
The momentum representation acts on the square integrable functions
and the norm of
φ is given by
The Schrödinger equation reads
3.3. Canonical position representation
The canonical position representation for the (
13) algebra is obtained from the momentum representation with replacing , as
The canonical position representation acts on the square integrable functions
and the norm of
ψ is given by
the Schrödinger equation reads
4. Eigenstates of momentum operator in the EUP position space
The momentum operators generating EUP position-space eigenstates are given by
or
This differential equation can be solved to obtain formal momentum eigenvectors
for the case of the equation (
36) reduces to , that is the plane wave. The wave function
ψp(
X) obeys the normalization condition
or
which means . Then, the normalized plane wave in the modified anti-de Sitter model is
Also, we can be calculate the Wave Function in a momentum representation and deformed exponential function by using the Jackson's
q-derivative [
23–
25] or Tsallis's
q-derivative [
26–
28].
5. Heisenberg algebra for a free particle by modified (anti)-de Sitter models
In this section, we write the Heisenberg algebra for both anti-de Sitter and de Sitter models for a free particle.
We assume the following algebra in anti-de Sitter space
and we have the following representation for above introduced commutation
On the other hand, we know the relation between commutator brackets in QM and Poisson brackets in CM is as follow
That is Poisson brackets.
Hamiltonian for a free particle is . Then, we obtain time evolution equations for position and momentum operators as [
29]
Then, by using equation (
46) and substituting in equation (
45) we obtain the following differential equation
By solving this differential equation, we obtain
which leads to
Now, we solve (anti)-de Sitter model for a free particle by using Heisenberg algebra
we obtain time evolution equations as
and substituting equation (
52) into equation (
51) leads to
For small values of
α in tan we have
In figure
1, we have plotted
X versus
t by using of equations (
49) and (
54).
Figure 1. Plot of the equation of motion under the EUP in the de Sitter space (black line) and the equation of motion under the EUP in the anti-de Sitter (dashed line) where we set P = m = 1 and α = 0.5. |
Full size|PPT slide
Then, by considering following commutation
From the Heisenberg algebra for a free particle, we write the time evolution equation as
and by substituting equation (
57) into equation (
56) we obtain
Then, by considering small values
α for sin
Also, in de Sitter model for a free particle
From the Heisenberg algebra, we write the time evolution equations as
Then, by substituting equation (
62) into equation (
61) we obtain
and for small values of
α for sinh, we have
Then, we know in equations (
49), (
54), (
59) and (
64) if
α tends to zero we obtain the standard equation.
6. Heisenberg algebra for Harmonic oscillator by modified (anti)-de Sitter models
In this section, we would like to obtain Heisenberg algebra by considering a harmonic oscillator potential [
30,
31].
Therefore, we consider the following modified (anti)-de Sitter models
For this commutation we have bellow representation
Considering the harmonic oscillator potential, Hamiltonian takes the following form
We write the Heisenberg equations of motion for X and P by using this representation and Hamiltonian
Now, we again use the Heisenberg equations of motion and Hamiltonian in order to obtain
in case
α = 0, equation (
70) leads to the ordinary relation
For nonzero values of
α, we have
For solving this equation using the successive approximation method, we consider
X as a function of the frequency
ω as [
32]
Substituting this term in equation (
72)
On the other hand, we have used expansion for the third term and considering it equals to zero
where
We see that deformed frequency in
α = 0 leads to the ordinary relation and is equal to ordinary frequency .
Now, in order to calculate the deformed frequency, we consider higher order
X in equation (
74) and we obtain the high order deformed frequency for EUP. Therefore, we add term to equation (
73) and by substituting it in equation (
72) we have
We neglect the sixth, seventh and eighth terms We regulate the terms versus coefficient and . Then, setting the first quantity in parentheses equal to zero gives the previous value for
ω in equation (
77)
where
Considering equation (
79) we obtain
Equation (
80) can be used to obtain the dynamical properties of the system.
In addition, we can use this method for solving the another commutation relation as
Thus, we obtain
Then, we obtain the modified equation
From the successive approximation method we have
And . Then, we obtain the dynamical properties of the system as
Also, we use this method for solving the following commutation
Then, we obtain the modified equation
From the successive approximation method, we have
And . Then, we obtain the dynamical properties of the system as
7. Particle in a uniform gravitational field for the GUP in (anti)-Snyder space
Heisenberg uncertainty principle modifies to GUP, by several investigations in string theory and quantum gravity (see, e.g. [
8,
9,
33]) GUP as
Where,
X and
P are position operator and momentum operator. Also, we define generalization parameter as . Where
β is of order the Planck mass and is of order the unity. Considering GUP and deformed momentum representation and we suggest the existence of the fundamental minimal length , which is of the order of the Planck’s length . The first algebra of this kind in the relativistic case was proposed by Snyder in 1947 [
34]. Also, recently Mignemi [
35] proposed the new model that is called the anti Snyder model by replacing
β with −
β as
The (anti)-Snyder models can be generalized into the following forms [
21]
The Hamiltonian equations of motion in space, in the uniform gravitation field are as follow
For anti-Snyder model, Considering Hamiltonian (
97), we have the following time evolution relations as [
29]
As a result, we obtain the momentum equation as
From the first equation, we obtain velocity as
As a result, by expanding these equations for small values of , we are able to obtain velocity and coordinate for anti-Snyder model as
When
β tends to zero, we will have the well known results
Considering Hamiltonian equation (
97), we obtain the following equations for Snyder model
Then, momentum can be obtained as
By substituting the previous equation in , we obtain velocity as
With using from expansion and Then for small values of for sinh and the sinh cubic terms, we obtain velocity and coordinate for the Snyder model as
Therefore, we are able to conclude time evolution equations for momentum and position for anti-Snyder model as
Then, from the second equation
By substituting
P in first equation we have
Therefore, for small values of , we can obtain these results for velocity and coordinate
We obtained the modified velocities and the modified coordinates in anti-Snyder and Snyder models which depends to
β parameter and in limited state changes to ordinary form.
7.1. Kinetic energy in the (anti)-Snyder space and parameter of deformation
In this section, we assume each particle of the system moves by the same velocity [
29]. Let us rewrite the kinetic energy as a function of velocity. From the relation between velocity and momentum for anti-Snyder model in equation (
98) we have
Then the kinetic energy as a function of velocity in the first order approximation of
β becomes
We see that the modified kinetic energy depends on
β parameter. Then, we repeat this solution for the equation (
105) which is GUP commutator for the Snyder space.
Then, the kinetic energy as a function of velocity in the first order approximation over
β becomes
The above equation is the modified kinetic energy for the Snyder space and depends on deformation parameter which in the special case has the ordinary form.
Also, from equation (
111) we have
Then, the kinetic energy as a function of velocity for the Snyder space in the first order approximation for
β reads
7.2. Heisenberg algebra for Harmonic oscillator by modified (anti)-Snyder models
In this section, we consider the following GUP in the Snyder and the anti-Snyder models as
Considering GUP and deformed momentum representation as [
10]
We consider the Hamiltonian equation (
67) for a harmonic oscillator and according to KMM algebra [
12], we obtain the Heisenberg equations of motion for
X and
P, by using this representation and Hamiltonian [
15]
Now, applying the solution method in section
7, we will have
or
To solve this equation, we consider
P depends on
ω frequency as follows
And substituting this term in the equation (
143)
On the other hand, using the expansion for term, we obtain the deformed frequency [
30,
32] as
where
We see that deformed frequency for the case that
β tends to zero leads to ordinary relation and equals to the ordinary frequency .
Now, we calculate the deformed frequency by considering higher order
P in equation (
129) and we obtain the high order deformed frequency for the GUP. Therefore, we add term to equation (
130) and we obtain
We neglect the sixth, seventh and eighth terms Then, we regulate the terms versus coefficient and . Then, considering the first quantity in parentheses equals zero give us the previous value for
ω in equation (
133)
where
Substituting equation (
138) into equation (
126) we obtain
Above equation can be used to obtain the dynamical properties of the system. In figure
2, we have plotted
X versus
t by using of equations (
80) and (
139).
Figure 2. Plot of the EUP oscillator in the de Sitter space (black line) and GUP oscillator in the Snyder space (dashed line) where we set X0 = P0 = m = ω = 1 and α = β = 0.5. |
Full size|PPT slide
Then, we repeat this solution for the another commutator in the Snyder and anti-Snyder space. we will be able to obtain time evolution for position and momentum as
Then, we obtain the modified equation
From the successive approximation method we have [
32]
And we obtain . Then, the dynamical properties of the system becomes
In fact, we obtained dynamical properties for Gup in the Snyder and anti-Snyder backgrounds and for EUP in the anti-de Sitter and de Sitter space that give us important results in the modified EUP and GUP field.
8. Conclusion
We have shown that there is another modified EUP in anti-de Sitter and de Sitter space–time, which we have written the representation in the position and the momentum space for. Also, we show that Heisenberg algebra for a free particle gives us a modified position equation that in special case ordinary results have been recovered. We have shown the Heisenberg equation of motion for EUP for Harmonic oscillator potential by solving through the successive approximation method, gives us the well-known results in the case of . In the non-zero state, we obtained the modified frequency for EUP and with successive approximation method we have obtained an equation in which the dynamical properties of the system are included. Also we introduced the modified anti-Snyder and snyder space for GUP and we have represented the Heisenberg algebra in the gravitational field given a modified kinetic energy for each of the commutations introduced. We are able to interpret this energy and find that it is a deformed form of ordinary energy and in the special case (β tends to zero) changes to previous form. Also, we have obtained modified coordinates and momentum for GUP in the Snyder and anti-Snyder background with harmonic oscillator potential. As we know, if the deformation parameter equals zero, we obtain the basic forms.
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