Physlib.QuantumMechanics.PoschlTeller.Basic
1d Pöschl-Teller
i. Overview
The Pöschl-Teller potential, ``, gives rise to a one-dimensional quantum system for which the energy eigenvalues, energy eigenstates and scattering data can be computed exactly. Notably, the potential is _reflectionless_ when the parameter controlling its depth is a positive integer.
ii. Key results
iii. Table of contents
- A. Potential function - B. Hilbert space - C. Operators - C.1. Kinetic energy - C.2. Potential energy - C.3. Hamiltonian - C.4. Creation and annihilation operators - C.4.1. On Schwartz functions - C.4.2. As unbounded operators - D. As a quantum system
iv. References
- https://arxiv.org/pdf/2411.14941
A. Potential function
B. Hilbert space
C. Operators
C.1. Kinetic energy
C.2. Potential energy
C.3. Hamiltonian
C.4. Creation and annihilation operators
#### C.4.1. On Schwartz functions
#### C.4.2. As unbounded operators
D. As a quantum system
28 declarations
Pöschl-Teller potential
The Pöschl-Teller potential function maps a position in one-dimensional space to the real value: where is the mass of the particle, is the reduced Planck's constant, is a parameter controlling the width of the potential, and is a parameter determining its depth.
Hilbert space for the Pöschl-Teller system
For a given Pöschl-Teller system, the Hilbert space is defined as , the space of square-integrable complex-valued functions on one-dimensional space.
Multiplication by as a continuous linear map
The continuous linear operator on the Schwartz space defined by pointwise multiplication by the function , where is the characteristic parameter of the Pöschl-Teller potential.
Creation operator for the Pöschl-Teller potential
The creation operator for a one-dimensional Pöschl-Teller system is a continuous linear map on the Schwartz space defined by the expression: where is the mass of the particle, is the characteristic parameter of the potential, is the momentum operator , is the reduced Planck constant, and is the imaginary unit. The operator involves the momentum operator and the pointwise multiplication by the hyperbolic tangent function .
Annihilation operator on the Schwartz space for the Pöschl-Teller potential
The annihilation operator for the one-dimensional Pöschl-Teller potential is defined as a continuous linear map on the Schwartz space . Given the system parameters for mass and the characteristic potential scale , the operator is expressed as: where is the momentum operator, is the reduced Planck constant, and denotes the operator for pointwise multiplication by the hyperbolic tangent function.
Multiplication operator by
The `tanhOperator` is the unbounded linear operator on the Hilbert space defined by the pointwise multiplication by the function , where is the characteristic parameter of the Pöschl-Teller potential. The operator maps a wave function to the product on the domain where this product remains square-integrable.
Creation operator for the Pöschl-Teller potential
For a one-dimensional Pöschl-Teller system with mass and characteristic parameter , the creation operator is an unbounded linear operator on the Hilbert space . It is defined as: where is the momentum operator, is the reduced Planck constant, and denotes the operator for pointwise multiplication by the hyperbolic tangent function.
Annihilation operator for the Pöschl-Teller system
The annihilation operator for the Pöschl-Teller system is an unbounded linear operator on the Hilbert space defined by the expression where is the momentum operator , is the mass of the particle, is the reduced Planck constant, and is the characteristic parameter of the Pöschl-Teller potential.
The Pöschl-Teller potential is even:
For the one-dimensional Pöschl-Teller potential , defined as the potential function is even, meaning that for any position in one-dimensional space, .
The function has temperate growth
For the one-dimensional Pöschl-Teller system with characteristic parameter , the function defined by has temperate growth. (A function has temperate growth if it and its derivatives are bounded by some polynomial at infinity).
The complexified function has temperate growth
For the parameter of the one-dimensional Pöschl-Teller potential, the complex-valued function defined by has temperate growth.
The Pöschl-Teller Potential Has Temperate Growth
The Pöschl-Teller potential function , defined as has temperate growth. A function is said to have temperate growth (or be slowly increasing) if it is smooth and all its derivatives are bounded by some polynomial. Here, is the particle mass, is the reduced Planck constant, and and are parameters characterizing the potential's shape.
The Complexified Pöschl-Teller Potential Has Temperate Growth
Let be the Pöschl-Teller potential defined by where is the mass of the particle, is the reduced Planck constant, and and are parameters characterizing the potential. Then the complex-valued function defined by the composition of the real-to-complex inclusion and (i.e., ) has temperate growth.
The Pöschl-Teller potential is continuous
The Pöschl-Teller potential function , defined as is continuous, where is the mass of the particle, is the reduced Planck constant, and and are parameters characterizing the potential.
1D Pöschl-Teller quantum system
The Pöschl-Teller system is defined as a one-dimensional quantum mechanical system (a `SpaceDQuantumSystem` with dimension ). It describes a particle of mass subject to the Pöschl-Teller potential: where is the reduced Planck's constant, and and are parameters determining the width and depth of the potential respectively. The structure includes the definition of the Hilbert space, the kinetic energy operator, the potential energy operator, and the total Hamiltonian .
The Dimension of the Pöschl-Teller System is
For a Pöschl-Teller quantum system , the spatial dimension of its underlying -dimensional quantum system structure is equal to .
The mass of the 1D Pöschl-Teller system equals
For a 1-dimensional Pöschl-Teller quantum system , the mass of the associated quantum mechanical system is equal to the mass defined within the Pöschl-Teller configuration.
The potential of the 1D Pöschl-Teller system is
For a one-dimensional Pöschl-Teller quantum system , the potential energy function is the Pöschl-Teller potential , which is defined as: where is the mass of the particle, is the reduced Planck's constant, is the width parameter, and is the depth parameter.
Action of the 1D Kinetic Energy Operator
For a one-dimensional Pöschl-Teller quantum system with particle mass , the kinetic energy operator (viewed as a continuous linear map on the Schwartz space ) acts on a Schwartz function according to: where is the momentum operator (the -th component in one dimension).
Pointwise Action of the Pöschl-Teller Potential Operator:
For a one-dimensional Pöschl-Teller quantum system , the potential operator (represented as a continuous linear map on the Schwartz space ) acts by pointwise multiplication. Specifically, for any Schwartz function and any position , the value of the resulting function at is: where is the Pöschl-Teller potential defined by .
The Pöschl-Teller potential operator is self-adjoint
In the one-dimensional Pöschl-Teller quantum system , the potential operator (the multiplication operator on the Hilbert space defined by the potential function ) is self-adjoint.
The Schwartz space is contained in the domain of the Pöschl-Teller potential operator
For a one-dimensional Pöschl-Teller quantum system , let denote the domain of the potential operator acting on the Hilbert space . The space of Schwartz functions is contained within the domain of the potential operator: This implies that for any Schwartz function , the product is square-integrable, where .
Pointwise action of the 1D Pöschl-Teller Hamiltonian
For a one-dimensional Pöschl-Teller quantum system with mass , the action of the Hamiltonian operator on a Schwartz function at a point is defined by the sum of the kinetic and potential energy components: where is the momentum operator and is the Pöschl-Teller potential function evaluated at .
Let denote the Schwartz space of complex-valued functions on the real line. For any function and any point , the continuous linear operator acts on via pointwise multiplication by the hyperbolic tangent function: where is the characteristic parameter associated with the Pöschl-Teller potential .
Pointwise action of the Pöschl-Teller creation operator
For any Schwartz function and any point , the pointwise action of the Pöschl-Teller creation operator is given by: where is the mass of the particle, is the characteristic parameter of the Pöschl-Teller potential, is the momentum operator, is the reduced Planck constant, and is the imaginary unit.
Pointwise Action of the Pöschl-Teller Annihilation Operator
For a Schwartz function and a point , the pointwise action of the annihilation operator for the one-dimensional Pöschl-Teller potential with mass and characteristic scale is given by: where is the momentum operator, is the reduced Planck constant, and is the imaginary unit.
For a one-dimensional Pöschl-Teller system with mass , the creation operator and the annihilation operator satisfy the following relation involving the momentum operator : This means that the sum of the ladder operators is equal to the momentum operator scaled by the factor .
for the Pöschl-Teller Potential
For a one-dimensional Pöschl-Teller system with mass and potential scale parameter , the difference between the creation operator and the annihilation operator acting on the Schwartz space is given by: where is the imaginary unit, is the reduced Planck constant, and denotes the operator for pointwise multiplication by the hyperbolic tangent function.
