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World Scientific series in 20th century physics

Penetration into Potential Barriers in Several Dimensions

P. L. KAPUR, Ronald F. Peierls

Published Apr 1, 1997• 0 citations
Publisher

Abstract

It is well known that in regions in which the refractive index varies sufficiently slowly, Schrodinger’s equation can be very simply treated by using its connexion with Hamilton-Jacobi’s differential equation. It is also known that a similar approximation is possible in regions of slowly varying imaginary refractive index (total reflexion). For the latter case the method was developed in papers by Jeffreys (1924), Wentzel (1926), Brillouin (1926) and Kramers (1926). These papers discuss also the behaviour of the wave function in the neighbourhood of the limit between the regions of real and imaginary refractive index. But although the connexion with the Hamilton-Jacobi equation holds in any number of dimensions, this equation can be solved by elementary means only in one dimension (or for problems that can by separation be reduced to one dimension), and for this reason the practical application of the method has so far been limited to one-dimensional or separable problems. In the present paper we discuss the case of more than one dimension and show that certain very simple inequalities may be obtained.

DOI
10.1142/9789812795779_0025

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It is well known that in regions in which the refractive index varies sufficiently slowly, Schrodinger’s equation can be very simply treated by using its connexion with Hamilton-Jacobi’s differential equation. It is also known that a similar approximation is possible in regions of slowly varying imaginary refractive index (total reflexion). For the latter case the method was developed in papers by Jeffreys (1924), Wentzel (1926), Brillouin (1926) and Kramers (1926). These papers discuss also the behaviour of the wave function in the neighbourhood of the limit between the regions of real and imaginary refractive index. But although the connexion with the Hamilton-Jacobi equation holds in any number of dimensions, this equation can be solved by elementary means only in one dimension (or for problems that can by separation be reduced to one dimension), and for this reason the practical application of the method has so far been limited to one-dimensional or separable problems. In the present paper we discuss the case of more than one dimension and show that certain very simple inequalities may be obtained.
Abstract It is well known that in regions in which the refractive index varies sufficiently slowly, Schrödinger’s equation can be very simply treated by using its connexion with Hamilton-Jacobi’s differential equation. It is also known that a similar approximation is possible in regions of slowly varying imaginary refractive index (total reflexion). For the latter case the method was developed in papers by Jeffreys (1924), Wentzel (1926), Brillouin (1926) and Kramers (1926). These papers discuss also the behaviour of the wave function in the neighbourhood of the limit between the regions of real and imaginary refractive index. But although the connexion with the Hamilton-Jacobi equation holds in any number of dimensions, this equation can be solved by elementary means only in one dimension (or for problems that can by separation be reduced to one dimension), and for this reason the practical application of the method has so far been limited to one-dimensional or separable problems. In the present paper we discuss the case of more than one dimension and show that certain very simple inequalities may be obtained.
The WKB approximation is a physically intuitive method and makes many connections with intuition about waves and classical mechanics as well as with results from the early days of quantum theory as it leads to the Bohr quantization condition. The WKB method is due to Gregor Wentzel, Hendrik Anthony Kramers and Leon Nicolas Brillouin. The method is applicable for slowly varying potentials, that is, the potentials that change not more than a few wavelengths. The WKB approximation is a physically intuitive method and makes many connections with intuition about waves and classical mechanics as well as with results from the early days of quantum theory as it leads to the Bohr quantization condition. The Schrödinger equation is solved to find the penetration of a square potential barrier. The WKB method is applied to obtain a transmission coefficient for penetration through a barrier.
This paper introduces a novel application of the Wentzel-Kramers-Brillouin (WKB) method to the Schrödinger equation, with the aim of incorporating certain nonlinear modifications that consider gravitational interaction within the wave function. By extending the traditional Schrödinger equation to account for gravitational effects, a new framework emerges, leading to two different sets of nonlinear differential equations for the gravitational potential, denoted as U . It is important to emphasize that these equations exhibit different characteristics and behaviors depending on the sign of U . The main objective of this study is to present a WKB method for the Schrödinger equation, which involves gravitational interactions in the wave function.The authors apply this method to derive two separate nonlinear differential equations for the gravitational potential U , considering both positive and negative values of U. The results reveal the intricate relationship between gravitational interactions and the behavior of the wave function, providing valuable insights into the dynamics of quantum systems under the influence of gravity. The presented WKB method extends our understanding of how gravitational effects affect quantum phenomena. As a novelty in this work, the integration of the WKB method with the Schrödinger equation is shown to address gravitational interactions. This unique approach opens new avenues for exploring quantum systems in the presence of gravity, which could lead to a deeper understanding of the fundamentals of quantum physics. Keywords: Nonlinear Differential Equation, Schrödinger Equation, Successive Approximations, The Wentzel-Kramers-Brillouin Method DOI: https://doi.org/10.35741/issn.0258-2724.58.4.66
A general Wentzel–Kramers–Brillouin (WKB) theory of multidimensional tunneling is formulated and an illuminating physical picture of the effects of multidimensionality is provided. Two basic problems are solved: (i) Maslov’s semiclassical wave function in the classically accessible region is connected to the wave function in the classically inaccessible region and (ii) the latter is propagated into the deep tunneling region. It is found that there exist two distinct types of tunneling: pure tunneling and mixed tunneling. The former is the usual one in which the tunneling path can be defined by a certain classical trajectory on the inverted potential and its associated action is pure imaginary. In the latter case, no tunneling path can be defined and the Huygens-type wave propagation should be carried out. In this case, tunneling is always accompanied by classical motion in the transversal direction and the associated action is complex. A general procedure is presented for the evaluation of energy splitting ΔE in the double well. Moreover, under the locally separable linear approximation, a simple and convenient formula for ΔE is derived and is confirmed to work well by comparison with the exact numerical calculations.