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Journal of Mathematical Physics

A class of solvable Pauli–Schrödinger Hamiltonians

Miguel Calvo, Simón Codriansky

Published Mar 1, 1983• 7 citations
Publisher

Abstract

The Pauli–Schrödinger equation for a spin 1/2, neutral particle with a nonvanishing magnetic moment μ0, interacting with an external scalar potential V and a static magnetic field B, both functions of only one of the coordinates, is solved exactly for four different choices of the potential and the field. By choosing in the examples the coordinate y, we present these solutions in the following cases: (i) V( y)=0, B( y)=(B0sin κy, 0, B0cos κy) where B0 and κ are two arbitrary constants. (ii) V( y)=λ′y2, B( y)=‖αy‖(cos 2κy, 0, sin 2κy) where 6* λ=ℏ2/2m and α,κ arbitrary constants and λ′=λ(μ0/2κλ)2. (iii) V( y)=λ′(c̄1tan αy+c̄2cot αy)2, B( y)=B( y) (sin (2κy+2δ(y)), 0, cos (2κy+2δ( y)) where B2( y)=(c̄1tan αy+c̄2cot αy)2 (+α2/4κ2)(c̄1sec2αy−c̄2csc2αy)2 and tan 2δ( y)=(2κ/λ)((c̄1tan αy+c̄2cot αy) /(c̄1sec2αy−c̄2csc2αy)); c̄1, c̄2, α, and κ are arbitrary constants. (iv) V( y)=λ′(ā tanh z+b̄)2 where z =[(y−cd)/d], B2( y)=(ā tanh z+b̄)2+(ā2/4κ2d2)sech2z, tan 2δ( y)=(2κd/ā)((ā tanh z+b̄)/sech2z); ā, b̄, c, d, and κ are arbitrary constants restricted only by (μ0/2κλ)ā2+ā/d>0. The functions B( y) and δ( y) define the vector B( y) as in (iii). Our method of solution is based on the familiar factorization technique for solving the Schrödinger eigenvalue equation. Several interesting physical results of these solutions are discussed.

DOI
10.1063/1.525727

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Spin ½: the Pauli theory

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Introduction The claim that it is impossible to construct a realistic physical model of quantum matter is often presented as definitively and finally proved in the case of systems with spin ½, or internal angular momentum of magnitude ħ/2, which exhibit a characteristic ‘nonclassical two-valuedness’. Nevertheless, the extension of the causal interpretation to embrace nonrelativistic spin ½ systems was successfully carried through in the 1950s (Bohm, Schiller & Tiomno, 1955; Bohm & Schiller, 1955; Takabayasi, 1955; Takabayasi & Vigier, 1957) and developed more recently (Dewdney, Holland & Kyprianidis, 1986, 1987a, b; Dewdney, Holland, Kyprianidis & Vigier, 1988). The idea is to assume that the spinor wave represents a new type of physical field propagating in spacetime that exerts an influence on a corpuscle moving within it. The additional information conveyed by the spinor beyond that contained in the spinless Schrödinger wave implies that the state of the particle is not exhausted by specifying its position and momentum, but that it is endowed with further properties such as an internal angular momentum. The equation governing the dynamics of the spinor wavefunction is the Pauli equation: where the Hamiltonian operator is given by Here e, m and μ are respectively the charge, mass and magnetic moment of the particle, A 0 and A are the electromagnetic potentials, B = ∇ × A is the magnetic field, V is any other external scalar potential, and σ is a vector whose components are the 2 × 2 Pauli matrices. The Hamiltonian (9.1.2) istherefore a 2 × 2 matrix operator and the wavefunction ψ( x , t ) has two complex components.

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8. Spin equation and its solutions

The aim of the present article is to study in detail the so-called spin equation (SE) and present both the methods of generating new solution and a new set of exact solutions.We recall that the SE with a real external field can be treated as a reduction of the Pauli equation to the (0 + 1)-dimensional case.Two-level systems can be described by an SE with a particular form of the external field.In this article, we also consider associated equations that are equivalent or (in one way or another) related to the SE.We describe the general solution of the SE and solve the inverse problem for this equation.We construct the evolution operator for the SE and consider methods of generating new sets of exact solutions.Finally, we find a new set of exact solutions of the SE.

De Gruyter eBooks•Aug 4, 2014•0 citations
The Pauli–Schrödinger equation for a spin 1/2, neutral particle with a nonvanishing magnetic moment μ0, interacting with an external scalar potential V and a static magnetic field B, both functions of only one of the coordinates, is solved exactly for four different choices of the potential and the field. By choosing in the examples the coordinate y, we present these solutions in the following cases: (i) V( y)=0, B( y)=(B0sin κy, 0, B0cos κy) where B0 and κ are two arbitrary constants. (ii) V( y)=λ′y2, B( y)=‖αy‖(cos 2κy, 0, sin 2κy) where 6* λ=ℏ2/2m and α,κ arbitrary constants and λ′=λ(μ0/2κλ)2. (iii) V( y)=λ′(c̄1tan αy+c̄2cot αy)2, B( y)=B( y) (sin (2κy+2δ(y)), 0, cos (2κy+2δ( y)) where B2( y)=(c̄1tan αy+c̄2cot αy)2 (+α2/4κ2)(c̄1sec2αy−c̄2csc2αy)2 and tan 2δ( y)=(2κ/λ)((c̄1tan αy+c̄2cot αy) /(c̄1sec2αy−c̄2csc2αy)); c̄1, c̄2, α, and κ are arbitrary constants. (iv) V( y)=λ′(ā tanh z+b̄)2 where z =[(y−cd)/d], B2( y)=(ā tanh z+b̄)2+(ā2/4κ2d2)sech2z, tan 2δ( y)=(2κd/ā)((ā tanh z+b̄)/sech2z); ā, b̄, c, d, and κ are arbitrary constants restricted only by (μ0/2κλ)ā2+ā/d>0. The functions B( y) and δ( y) define the vector B( y) as in (iii). Our method of solution is based on the familiar factorization technique for solving the Schrödinger eigenvalue equation. Several interesting physical results of these solutions are discussed.
From the early days of Quantum Physics, one basic problem arose. The problem of population transfer in an n-level quantum system, i.e., the transition from an initial state ∣i⟩\ket{i}∣i⟩ to a final one ∣f⟩.\ket{f}.∣f⟩. In recent years, there has been a renewed interest in this problem as a result of the capability to construct nanostructures that behave like atoms. Those nanostructures can be used in the rapidly developing area of Quantum Information and Computation and, in general, of Quantum Technology, as they can serve as successful candidates for the creation of entangled photons and quantum gates. The existence of the latter is detrimental for the implementation of quantum computers. But, a necessary precondition for the use of those structures, is the coherent preparation of their states. \par The latter is the purpose of this work. In particular, we study theoretically, the potential for controlled population transfer in a hybrid nanostructure comprised of a semiconductor quantum dot and a metallic nanoparticle. The system interacts with a laser pulse which induces the desired population transfer from the ground to the biexciton state. The nanoparticle is treated as a classical particle and its effect is the enhancement of the electric field in the area of the quantum dot. In this thesis, we derive the density matrix equations that describe the dynamics of the system. We solve them numerically and\textemdash whenever possible\textemdash analytically and derive the necessary conditions for the desired population transfer, for pulses with constant or time-dependent frequency (chirped pulses). We note that the results of the latter method are original and are ready for publication.
Introduction The claim that it is impossible to construct a realistic physical model of quantum matter is often presented as definitively and finally proved in the case of systems with spin ½, or internal angular momentum of magnitude ħ/2, which exhibit a characteristic ‘nonclassical two-valuedness’. Nevertheless, the extension of the causal interpretation to embrace nonrelativistic spin ½ systems was successfully carried through in the 1950s (Bohm, Schiller & Tiomno, 1955; Bohm & Schiller, 1955; Takabayasi, 1955; Takabayasi & Vigier, 1957) and developed more recently (Dewdney, Holland & Kyprianidis, 1986, 1987a, b; Dewdney, Holland, Kyprianidis & Vigier, 1988). The idea is to assume that the spinor wave represents a new type of physical field propagating in spacetime that exerts an influence on a corpuscle moving within it. The additional information conveyed by the spinor beyond that contained in the spinless Schrödinger wave implies that the state of the particle is not exhausted by specifying its position and momentum, but that it is endowed with further properties such as an internal angular momentum. The equation governing the dynamics of the spinor wavefunction is the Pauli equation: where the Hamiltonian operator is given by Here e, m and μ are respectively the charge, mass and magnetic moment of the particle, A 0 and A are the electromagnetic potentials, B = ∇ × A is the magnetic field, V is any other external scalar potential, and σ is a vector whose components are the 2 × 2 Pauli matrices. The Hamiltonian (9.1.2) istherefore a 2 × 2 matrix operator and the wavefunction ψ( x , t ) has two complex components.
We consider the functional Hamilton–Jacobi (HJ) equation, which is the central equation of the holographic renormalization group (HRG), functional Schrödinger equation, and generalized Wilson–Polchinski (WP) equation, which is the central equation of the functional renormalization group (FRG). These equations are formulated in D-dimensional coordinate and abstract (formal) spaces. Instead of extra coordinates or an FRG scale, a “holographic” scalar field Λ is introduced. The extra coordinate (or scale) is obtained as the amplitude of delta-field or constant-field configurations of Λ. For all the functional equations above a rigorous derivation of corresponding integro-differential equation hierarchies for Green functions (GFs) as well as the integration formula for functionals are given. An advantage of the HJ hierarchy compared to Schrödinger or WP hierarchies is that the HJ hierarchy splits into independent equations. Using the integration formula, the functional (arbitrary configuration of Λ) solution for the translation-invariant two-particle GF is obtained. For the delta-field and the constant-field configurations of Λ, this solution is studied in detail. A separable solution for a two-particle GF is briefly discussed. Then, rigorous derivation of the quantum HJ and the continuity functional equations from the functional Schrödinger equation as well as the semiclassical approximation are given. An iterative procedure for solving the functional Schrödinger equation is suggested. Translation-invariant solutions for various GFs (both hierarchies) on delta-field configuration of Λ are obtained. In context of the continuity equation and open quantum field systems, an optical potential is briefly discussed. The mode coarse-graining growth functional for the WP action (WP functional) is analyzed. Based on this analysis, an approximation scheme is proposed for the generalized WP equation. With an optimized (Litim) regulator translation-invariant solutions for two-particle and four-particle amputated GFs from approximated WP hierarchy are found analytically. For Λ=0 these solutions are monotonic in each of the momentum variables.
Abstract This work introduces the C3–Quantum Geometry as a foundational extension of quantum mechanics, built upon the cubic algebra j3=−1j^{3} = -1j3=−1. By promoting the complex plane to a three-phase geometry, the theory unifies time, space, and energy within a single algebraic and differential cycle. The state function ψ=a+jb+j2c\psi = a + j b + j^{2} cψ=a+jb+j2c is interpreted not as a mere multicomponent wave, but as a cyclic triplet of position, velocity, and curvature — the differential closure of physical motion. The C3–Hilbert space introduces a positive-definite measure ∥ψ∥phys2=a2+b2+c2,\|\psi\|^{2}_{\mathrm{phys}} = a^{2} + b^{2} + c^{2},∥ψ∥phys2=a2+b2+c2, where the visible and hidden curvature axes, j−j2j - j^{2}j−j2 and j+j2j + j^{2}j+j2, separate measurable and latent quantum contributions. The corresponding C3–Schrödinger equation (j ℏ ∂t+j2γ∇2+μ)ψ=0(j\,\hbar\,\partial_{t} + j^{2}\gamma\nabla^{2} + \mu)\psi = 0(jℏ∂t+j2γ∇2+μ)ψ=0 restores the standard Schrödinger law as its visible branch while maintaining a closed cubic dynamic (L3+1)ψ=0(L^{3} + 1)\psi = 0(L3+1)ψ=0. This structure yields a new geometrical origin for uncertainty: Δx Δp=ℏ2 eα(R(3)−K),\Delta x\,\Delta p = \frac{\hbar}{2}\,e^{\alpha(R^{(3)} - K)},ΔxΔp=2ℏeα(R(3)−K), where the difference between spatial curvature R(3)R^{(3)}R(3) and temporal curvature KKK determines the observable quantum indeterminacy. The C3 framework therefore transforms the wavefunction into a full geometric object — a phase–curvature tensor uniting time, space, and energy through differential closure, Hermitian balance, and measurable norm preservation.
The aim of the present article is to study in detail the so-called spin equation (SE) and present both the methods of generating new solution and a new set of exact solutions.We recall that the SE with a real external field can be treated as a reduction of the Pauli equation to the (0 + 1)-dimensional case.Two-level systems can be described by an SE with a particular form of the external field.In this article, we also consider associated equations that are equivalent or (in one way or another) related to the SE.We describe the general solution of the SE and solve the inverse problem for this equation.We construct the evolution operator for the SE and consider methods of generating new sets of exact solutions.Finally, we find a new set of exact solutions of the SE.