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arXiv:1308.3921

The Theory of Discrete Extension -- An Operator-Free Approach To Quantization

John T. Brooker

Published Aug 19, 2013• 0 citations
arXivHTMLPDF

Abstract

The theory of discrete extension, introduced here, demonstrates that various re-sults from elementary, non-relativistic quantum mechanics can be obtained without recourse to eigenvalue problems, operators, or state vectors in Hilbert space. Us-ing a mathematical structure similar to that of Newtonian mechanics, the theory generates correct, quasi-discrete values of action increments and energy levels for bound states of quantum-level systems. Quantization of the harmonic oscillator provides a simple illustration. Like Newtonian mechanics the theory provides intuitive conceptualizations for basic entities and kinematics. However, in place of the classical concepts of particle and field, the non-classical, unitary concept of a discretely extended ob-ject emerges from the theory as an alternative characterization of the nature of quantum-level entities. Because such an object is well-defined and unitary, the theory avoids the dilemmas of wave-particle dualism and complementarity. The theory offers insight into the nature of a number of quantum effects such as the zero-point energy of a harmonic oscillator. It also makes a number of testable predictions that distinguish it from standard quantum theory and from Bohmian mechanics.

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The theory of discrete extension, introduced here, demonstrates that various re-sults from elementary, non-relativistic quantum mechanics can be obtained without recourse to eigenvalue problems, operators, or state vectors in Hilbert space. Us-ing a mathematical structure similar to that of Newtonian mechanics, the theory generates correct, quasi-discrete values of action increments and energy levels for bound states of quantum-level systems. Quantization of the harmonic oscillator provides a simple illustration. Like Newtonian mechanics the theory provides intuitive conceptualizations for basic entities and kinematics. However, in place of the classical concepts of particle and field, the non-classical, unitary concept of a discretely extended ob-ject emerges from the theory as an alternative characterization of the nature of quantum-level entities. Because such an object is well-defined and unitary, the theory avoids the dilemmas of wave-particle dualism and complementarity. The theory offers insight into the nature of a number of quantum effects such as the zero-point energy of a harmonic oscillator. It also makes a number of testable predictions that distinguish it from standard quantum theory and from Bohmian mechanics.
Quantum mechanics can be formulated either in terms of matrix mechanics or in terms of wave mechanics. This chapter centers on a discussion of the historical origins, mathematical structure, and extension to non-Hermitian quantum theory of matrix mechanics. The development of atomic discrete spectra and the old quantum theory showed that classical mechanics could not account for the discreteness of atomic energy levels and spectral lines, which motivated Heisenberg, Born, Jordan, and others to establish matrix mechanics centered on noncommuting physical quantities. Combining the Bohr atomic model, angular momentum quantization, and radiative transitions, one can see how matrix mechanics describes the energy level structure and quantum transitions of atomic systems, and how the Heisenberg equation of motion gives the fundamental form of quantum dynamics. The example of the harmonic oscillator further shows that the discreteness of the energy spectrum can be obtained directly from the matrix method, thereby establishing a clear connection among transition frequencies, matrix elements, and radiation-induced transitions. The matrix representation corresponds to the operator theory in Hilbert space, where state vectors, inner products, complete bases, and spectral decomposition constitute the fundamental mathematical framework of quantum mechanics. For closed quantum systems, physical observables are generally required to be represented by Hermitian or self-adjoint operators, so as to ensure that their eigenvalues possess the physically acceptable property of being real numbers. The Hermiticity of an operator is also closely related to its domain and boundary conditions, which provides a mathematical possibility for the emergence of non-Hermitian Hamiltonians. Based on these discussions, this chapter further explains how non-Hermitian dynamics is connected with open systems, dissipative processes, and special boundary conditions, thereby demonstrating the natural connection between traditional matrix mechanics and modern non-Hermitian quantum theory.
We discuss the principles to be used in the construction of discrete time classical and quantum mechanics as applied to point particle systems. In the classical theory this includes the concept of virtual path and the construction of system functions from classical Lagrangians, Cadzow's variational principle applied to the action sum, Maeda - Noether and Logan invariants of motion, elliptic and hyperbolic harmonic oscillator behaviour, gauge invariant electrodynamics and charge conservation, and the Grassmannian oscillator. First quantized discrete time mechanics is discussed via the concept of system amplitude, which permits the construction of all quantities of interest such as commutators and scattering amplitudes. We discuss stroboscopic quantum mechanics, or the construction of discrete time quantum theory from continuous time quantum theory and show how this works in detail for the free Newtonian particle. We conclude by applying the Schwinger action principle to the important case of the quantized discrete time inhomogeneous oscillator.
We start by rewriting classical mechanics in a quantum mechanical fashion and point out that the only difference with quantum theory re- sides at one point. There is a classical analogon of the collapse of the wavefunction and an extension of the usual Born rule is proposed which might solve this problem. We work only with algebra’s over the real (com- plex) numbers, general number fields of finite characteristic allowing for finite dimensional representations of the commutation relations are not considered given that such fields are not well ordered and do not give rise to a well defined probability interpretation. Our theory generalizes however to discrete spacetimes and finite dimensional algebra’s. Looking at physics this way, spacetime itself distinguishes itself algebraically by means of well chosen commutation relations and there is further nothing special about it meaning it has also a particle interpretation just like any other dynamical variable. Likewise, there is no reason for the dynamics to be Hamiltonian and therefore we have a nonconservative formulation of quantum physics at hand. The harmonic oscillator (amongst few oth- ers) distinguishes itself because the algebra forms a finite dimensional Lie algebra; the classical and quantum (discrete) harmonic oscillator are stud- ied in a some more generality and examples are given which are neither classical, nor quantum.
An interpretation and re-formulation of modern physics which removes the presumption of the space-time continuum, and bases physical theory on a small number of rational and empirical principles. After briefly describing the philosophical principles underlying the theory, we rigorously construct a discrete model of quantum mechanics. Kets are names, or labels which categorise states of matter but do not directly describe them. The principle of superposition is seen as a definitional truism in the categorisation of states. This resolves the measurement problem of quantum mechanics by attributing the collapse of the wave function to information. The probability interpretation has a natural meaning in which the configuration of interacting particles plays the role of a hidden variable. The model supports a form of relativistic quantum field theory which does not depend on quantisation or second quantisation from classical mechanics. Continuous laws of wave mechanics are found in a discrete metaphysic which does not involve waves. Classical law is the expected behaviour of many elementary particles. The constraints on the theory are sufficient to establish that particles are point-like entities with specific properties found in nature. Newton's first law and conservation of momentum are established from the principle of homogeneity. Maxwell's equations are derived from the simple interaction in which a Dirac particle emits or absorbs a photon. Feynman rules are calculated for the discrete theory and differ from the standard rules by the removal of the ultraviolet divergence and the use of proper loop integrals. They give finite and unambiguous results.
This pedagogical paper synthesizes a coherent conceptual pathway from the mode expansion of free quantum fields to the continuous dynamics of resonant energy exchange in two-level systems. We clarify several recurrent points of confusion: (i) the fixed characteristic frequency of a quantum harmonic oscillator across its number states; (ii) the relation between spatial nodes of energy eigenfunctions and the principal quantum number in atomic orbitals; (iii) the interpretation of complex-conjugate mode functions as counter-propagating waves; (iv) the analogy—and the limits of that analogy—between discrete mode spectra of classical strings and quantum energy quantization; and (v) the continuous, unitary character of radiative transitions mediated by Rabi oscillations. Particular emphasis is placed on the mathematical isomorphism between the Schrödinger dynamics of probability amplitudes and the Newtonian dynamics of a classical harmonic oscillator governed by Hooke’s law. The discussion is intended as a self-contained resource for students and non-specialists seeking a unified intuitive picture that remains faithful to the underlying quantum theory.
Quantum mechanics of a linear harmonic oscillator in a finite-dimensional Hilbert space satisfying the correct equations of motion is studied. The connections to Weyl's formulation of the algebra of bounded unitary operators in finite space as well as to a truncated quantized linear harmonic oscillator are discussed. It is pointed out that the discrete Fourier transformation (DFT) plays a central role in determining the actual form of the position, the momentum, the number and the Hamiltonian operators. The explicit form of these operators in different bases is exhibited for some low values of the dimension of the Hilbert space. In this formulation, it is shown that the Hamiltonian is indeed the logarithm of the DFT and that by modifying Weyl's framework to include position and momentum operators with non-uniformly spaced spectra the equations of motion are satisfied.