Physlib.QuantumMechanics.DDimensions.Basic
Single-particle quantum system on `Space d`
i. Overview
In this module we introduce the general notion of a single-particle quantum system on `Space d`.
The structure `SpaceDQuantumSystem` encompasses the basic information needed to specify the system, namely the number of spatial dimensions, the particle's mass and the potential function.
ii. Key results
iii. Table of contents
- A. Basic properties - B. Operators - B.1. Kinetic energy - B.2. Potential energy - B.3. Hamiltonian
iv. References
A. Basic properties
B. Operators
B.1. Kinetic energy
B.2. Potential energy
B.3. Hamiltonian
20 declarations
Hilbert space of the quantum system
For a single-particle quantum system with spatial dimension , the associated Hilbert space is defined as , the space of square-integrable complex-valued functions on the -dimensional space .
The mass of the particle is strictly positive ()
In a single-particle quantum system as defined in `SpaceDQuantumSystem`, let denote the mass of the particle. The mass is strictly positive, satisfying .
The mass of a quantum system is non-negative:
In a single-particle quantum system , the mass of the particle is non-negative, satisfying .
Mass
For a single-particle quantum system , let be the mass of the particle. Then the mass is non-zero, i.e., .
Kinetic energy operator as a continuous linear map
For a single-particle quantum system with mass and spatial dimension , the kinetic energy operator is defined as the continuous linear map given by: where is the momentum operator and is the Schwartz space of rapidly decreasing functions on the -dimensional space.
The kinetic energy operator
For a single-particle quantum system with mass and spatial dimension , the kinetic energy operator , defined as a continuous linear map on the Schwartz space , is equal to the momentum operator vector squared divided by twice the mass: where (or ) denotes the dot product of the momentum operator with itself.
Kinetic energy operator
For a single-particle quantum system with mass and spatial dimension , the kinetic energy operator is an unbounded linear operator on the Hilbert space defined by: where is the momentum-squared operator. The domain of the operator is the Schwartz space .
Kinetic energy operator
For a single-particle quantum system with mass , the kinetic energy operator is equal to the momentum-squared operator scaled by the factor :
Potential operator on the Schwartz space
For a quantum system in dimensions with potential function , the potential operator is the continuous linear map from the Schwartz space to itself defined by pointwise multiplication. Specifically, for any Schwartz function , the operator maps to the function .
The potential operator is the multiplication operator by the potential function
For a -dimensional single-particle quantum system with potential function , the potential operator (defined as a continuous linear map on the Schwartz space ) is equal to the operator of pointwise multiplication by . That is, , where denotes the potential function cast into complex values and denotes the continuous linear map corresponding to left scalar multiplication.
The potential operator on Schwartz space is pointwise multiplication by the potential function
For a quantum system in dimensions with potential function , if has temperate growth, then the potential operator applied to a Schwartz function is the function given by pointwise multiplication: for all .
Pointwise evaluation of the potential operator
Let be a single-particle quantum system in dimensions with a potential function . If has temperate growth, then for any wave function in the Schwartz space and any point , the potential operator applied to and evaluated at is given by the pointwise product: where denotes the scalar multiplication of the potential value at and the value of the wave function at .
Potential operator as a multiplication operator
For a single-particle quantum system in dimensions with a real-valued potential function , the potential operator (denoted by `potentialOperator`) is the partially defined (unbounded) linear operator on the Hilbert space that maps a wave function to the pointwise product . The domain of this operator is the set of all such that the resulting product is also square-integrable.
The potential operator is the multiplication operator
For a single-particle quantum system in dimensions with a real-valued potential function , the potential operator is defined as the multiplication operator associated with the complex-valued function obtained by embedding into the complex numbers.
The potential operator is self-adjoint if the potential is almost everywhere strongly measurable
For a single-particle quantum system in dimensions with a real-valued potential function , if is almost everywhere strongly measurable, then the potential operator (the multiplication operator acting on the Hilbert space ) is self-adjoint.
The Schwartz space is contained in the domain of the potential operator for potential functions with temperate growth
For a single-particle quantum system in dimensions with potential function , if has temperate growth, then the Schwartz space is contained within the domain of the potential operator .
Hamiltonian operator on Schwartz space
For a single-particle quantum system in dimensions, the Hamiltonian operator is the continuous linear map from the Schwartz space to itself defined as the sum of the kinetic energy operator and the potential energy operator : where is the kinetic energy operator `kineticCLM` and is the potential energy operator `potentialCLM`. This definition assumes the potential function has temperate growth to ensure the operator is well-defined on the Schwartz space.
Hamiltonian Operator on Schwartz Space
For a single-particle quantum system in dimensions, the Hamiltonian operator is equal to the sum of the kinetic energy operator and the potential energy operator , where each is defined as a continuous linear map on the Schwartz space : Here, represents the operator and represents the operator of pointwise multiplication by the potential function.
Hamiltonian operator
For a single-particle quantum system with spatial dimension , the Hamiltonian operator is the unbounded linear operator on the Hilbert space defined as the sum of the kinetic energy operator and the potential energy operator : This operator is a symmetric unbounded operator on the system's Hilbert space.
The Hamiltonian operator equals
For a single-particle quantum system in dimensions, the Hamiltonian operator is equal to the sum of the kinetic energy operator and the potential energy operator : These operators are defined as unbounded linear operators on the system's Hilbert space .
