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Physlib.QuantumMechanics.InfiniteSquareWell.Basic

The infinite square well

i. Overview

The particle in an infinite square well is one of the simplest quantum systems. The domain is an axis-aligned cuboid (the well) and energy eigenstates are (products of) trigonometric functions satisfying appropriate boundary conditions.

ii. Key results

iii. Table of contents

  • A. Basic properties
  • B. Domain
  • C. Hilbert space
  • D. Hamiltonian
  • E. As a quantum system

iv. References

A. Basic properties

B. Domain

C. Hilbert space

D. Hamiltonian

E. As a quantum system

9 declarations

theorem

The mass mm of the particle in an infinite square well is strictly positive

For an infinite square well QQ, the mass mm of the particle is strictly positive, such that 0<m0 < m.

theorem

The mass mm of a particle in an infinite square well is non-negative (m0m \ge 0)

For a particle in an infinite square well QQ, the mass mm of the particle is non-negative, satisfying 0m0 \le m.

theorem

The mass mm of the particle in the infinite square well is non-zero (m0m \neq 0).

For an infinite square well system QQ, the mass mm of the particle is non-zero, i.e., m0m \neq 0.

definition

Domain of the infinite square well [Q.lower,Q.upper][Q.\text{lower}, Q.\text{upper}]

The domain of an infinite square well QQ in dd dimensions is the set of points in the space that fall within the axis-aligned cuboid defined by the dd-dimensional closed interval [Q.lower,Q.upper][Q.\text{lower}, Q.\text{upper}]. Mathematically, it is the preimage of the closed interval [Q.lower,Q.upper][Q.\text{lower}, Q.\text{upper}] under the coordinate valuation map of the space.

definition

Lebesgue measure restricted to the well domain Q.wellQ.\text{well}

The measure μ\mu on the dd-dimensional space Space d\text{Space } d associated with an infinite square well QQ is defined as the standard Lebesgue measure (denoted as `volume`) restricted to the well's domain Q.wellQ.\text{well}. Mathematically, for any measurable set ASpace dA \subseteq \text{Space } d, the measure is given by μ(A)=λ(AQ.well)\mu(A) = \lambda(A \cap Q.\text{well}), where λ\lambda is the Lebesgue measure and Q.wellQ.\text{well} is the axis-aligned cuboid defined by the interval [Q.lower,Q.upper][Q.\text{lower}, Q.\text{upper}].

abbrev

Hilbert space L2(Space d,C)L^2(\text{Space } d, \mathbb{C}) for the infinite square well

For an infinite square well QQ in a dd-dimensional space, the Hilbert space is defined as the space L2(Space d,C)L^2(\text{Space } d, \mathbb{C}) of complex-valued square-integrable functions, where the underlying measure is the Lebesgue measure restricted to the well's domain Q.well=[Q.lower,Q.upper]Q.\text{well} = [Q.\text{lower}, Q.\text{upper}].

definition

Hamiltonian H=12mp^2H = \frac{1}{2m} \hat{p}^2 for the infinite square well

The Hamiltonian operator HH for a particle of mass mm in an infinite square well is defined as H=12mp^2H = \frac{1}{2m} \hat{p}^2, where p^2\hat{p}^2 is the momentum squared operator acting on the Hilbert space defined by the measure of the well.

definition

The Hamiltonian HH of the infinite square well is essentially self-adjoint

The Hamiltonian operator HH for a particle in an infinite square well is essentially self-adjoint on its domain in the Hilbert space.

definition

Infinite square well quantum system

This definition constructs the quantum mechanical system for a particle in an infinite square well. The system is defined by a Hilbert space H=L2(Ω)\mathcal{H} = L^2(\Omega) over an axis-aligned cuboid ΩRn\Omega \subset \mathbb{R}^n and a self-adjoint Hamiltonian operator HH acting on this space, representing the particle's energy under Dirichlet boundary conditions.