Relativistic Confinement of Neutral Fermions with Partially Exactly Solvable and Exactly Solvable PT-Symmetric Potentials in the Presence of Position-Dependent Mass

The relativistic problems of neutral fermions subject to a new partially exactly solvable PT-symmetric potential and an exactly solvable PT-symmetric hyperbolic cosecant potential in 1+1 dimensions are investigated. The Dirac equation with the double-well-like mass distribution in the background of the PT-symmetric vector potential coupling can be mapped into the Schrödinger-like equation with the partially exactly solvable double-well potential. The position-dependent effective mass Dirac equation with the PT-symmetric hyperbolic cosecant potential can be mapped into the Schrödinger-like equation with the exactly solvable modified Pöschl-Teller potential. The real relativistic energy levels and corresponding spinor wavefunctions for the bound states have been given in a closed form.     

平均场加区分质子和中子的邻近轨道对力模型及对超铀区核的统一描述

利用严格可解的平均场加区分质子和中子的邻近轨道相互作用对力模型,对超铀区部分大形变核进行了统一的描述.计算了^227—233Th,^232—239U,^236—243Pu同位素和同中异质素²²⁸Ra-²²⁹Ac-²³⁰Th-²³¹Pa-²³²U,²³²Th-²³³Pa-²³⁴U-²³⁵Np-²³⁶Pu,²³⁶U-²³⁷Np-²³⁸Puv-²³⁹Am的结合能,对激发能和奇偶能差并与相应核的实验值进行了比较     

Many-phonon processes and the interaction of spinless quasiparticles with lattice vibrations at finite temperature

Using diagram techniques, we present an exact system of equations for the total mass operator of spinless quasiparticles interacting with phonons at finite temperature. The mass operator is then represented in the form of a branching fraction and the n-th arbitrary term is determined exactly. Using an exactly solvable example, it is shown that this representation of the mass operator can be used to take into account many-phonon processes generating the spectrum of the quasiparticles in an efficient way.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 93–98, October, 1986.     

Similarity solutions of reaction–diffusion equation with space- and time-dependent diffusion and reaction terms

We consider solvability of the generalized reaction–diffusion equation with both space- and time-dependent diffusion and reaction terms by means of the similarity method. By introducing the similarity variable, the reaction–diffusion equation is reduced to an ordinary differential equation. Matching the resulting ordinary differential equation with known exactly solvable equations, one can obtain corresponding exactly solvable reaction–diffusion systems. Several representative examples of exactly solvable reaction–diffusion equations are presented.     

Liouville Transformation and Exactly Solvable Schrodinger Equations

The present paper discusses the connectionbetween exactly solvable Schrodinger equations and theLiouville transformation. This transformation yields alarge class of exactly solvable potentials, including the exactly solvable potentials introduced byNatanzon. In addition, this class is shown to containtwo new families of exactly solvablepotentials.     

Random matrix theories and exactly solvable models

A connection between random-matrix theories and exactly solvable models is discussed here. This is done in three parts: firstly, for theWigner—Dyson case; secondly, for the short-range Dyson case; and thirdly, for the pseudo-Hermitian one. The exactly solvable models are variants and extensions of Calogero—Sutherland—Moser systems.     

Chiral Thirring–Wess model

The vector type of interaction of the Thirring–Wess model was replaced by the chiral type and a new model was presented which was termed as chiral Thirring–Wess model in Rahaman (2015). The model was studied there with a Faddeevian class of regularization. Few ambiguity parameters were allowed there with the apprehension that unitarity might be threatened like the chiral generation of the Schwinger model. In the present work it has been shown that no counter term containing the regularization ambiguity is needed for this model to be physically sensible. So the chiral Thirring–Wess model is studied here without the presence of any ambiguity parameter and it has been found that the model not only remains exactly solvable but also does not lose the unitarity like the chiral generation of the Schwinger model. The phase space structure and the theoretical spectrum of this new model have been determined in the present scenario. The theoretical spectrum is found to contain a massive boson with ambiguity free mass and a massless boson.     

On askey-wilson algebra

The ladder representations of Askey-Wilson algebra (AWA) is investigated and the over-lap problem is discussed. The full class of exactly solvable potentials for one-dimensional ordinary Schrödinger equation with the AWA as an algebra of dynamical symmetry is found for creation-annihilation operators of third order. The generating spectrum algebra for latticeSchrödinger equation as AWA is examined. All exactly solvable potentials with this dynamical symmetry are found. Some generalizations of obtained results are discussed.     

Path integral approach to polaron mass and radius at finite temperatures

Polaron effective mass and radius at finite temperatures are defined and exact path integral representations are given for them. Feynman's representation for the effective mass is obtained in the limit of zero temperature. Calculations are made in the framework of the variational principle for the free energy by using as trial functional the one corresponding to a simplified, exactly solvable model of electron-phonon interaction proposed by Bogolubov. Effective mass and radius dependence on temperature and coupling strength are discussed for some ranges of values of these parameters. Comparison with the experimental dependence of polaron cyclotron mass on temperature shows a reasonable agreement.     

Remarks on Exact Solvability of Quantum Systems with Spatially Varying Effective Mass

Within the frame of a novel treatment we make a complete mathematical analysis of exactly solvable onedimensional quantum systems with non-constant mass, involving their ordering ambiguities. This work extends the results recently reported in the literature and clarifies the relation between physically acceptable effective mass Hamiltonians.     

Spatio-temporal history of decay

The decay process of a metastable excited state is studied in this Letter. We have modeled the system as a particle of finite mass coupled to a continuum of excitations and it is found that the excitations move instantaneously in space. We discuss our observations in connection with Fermi's two atom problem and Hegerfeldt's theorem. Our observations confirm Hegerfeldt's theorem for an exactly solvable and experimentally realizable model.     

The Maxwell and Proca equations in spaces with torsion

Nonlinear equations are derived for mass as well as massless vector fields in a Riemann space, where nonlinearity is induced by the interaction of these fields with individual irreducible parts of the torsion tensor. It is shown that in the simplest cases these equations are exactly solvable for an electromagnetic field, while a mass field is described by a number of interesting equations, in particular the sinh-Gordon equation, which has soliton solutions.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 28–32, January, 1982.     

Complex oscillator and Painlevé IV equation

Supersymmetric quantum mechanics is a powerful tool for generating exactly solvable potentials departing from a given initial one. In this article the first- and second-order supersymmetric transformations will be used to obtain new exactly solvable potentials departing from the complex oscillator. The corresponding Hamiltonians turn out to be ruled by polynomial Heisenberg algebras. By applying a mechanism to reduce to second the order of these algebras, the connection with the Painlevé IV equation is achieved, thus giving place to new solutions for the Painlevé IV equation.     

Exceptional orthogonal polynomials and exactly solvable potentials in position dependent mass Schrödinger Hamiltonians

Some exactly solvable potentials in the position dependent mass background are generated whose bound states are given in terms of Laguerre- or Jacobi-type X₁ exceptional orthogonal polynomials. These potentials are shown to be shape invariant and isospectral to the potentials whose bound state solutions involve classical Laguerre or Jacobi polynomials.     

Exactly solvable two-dimensional stationary Schrödinger operators obtained by the nonlocal Darboux transformation

The Fokker–Planck equation associated with the two-dimensional stationary Schrödinger equation has the conservation law form that yields a pair of potential equations. The special form of Darboux transformation of the potential equations system is considered. As the potential variable is a nonlocal variable for the Schrödinger equation that provides the nonlocal Darboux transformation for the Schrödinger equation. This nonlocal transformation is applied for obtaining of the exactly solvable two-dimensional stationary Schrödinger equations. The examples of exactly solvable two-dimensional stationary Schrödinger operators with smooth potentials decaying at infinity are obtained.     

New type of exactly solvable potential

It is shown that, starting from an exactly solvable potential and making use of the theory of a system of coupled differential equations, it is possible to construct a new type of second-generation potential which is also exactly solvable.     

Mass Generation in a Fermionic Model with Finite Range Time Dependent Interactions

Bardeen, Cooper and Schrieffer in their paper on the theory of superconductivity introduced a model of interacting fermions (BCS model) in which the (instantaneous) interaction is only between electrons of opposite momentum and spin (Cooper pairs). Subsequently it was claimed that in the thermodynamic limit the BCS model is equivalent to the (exactly solvable) quadratic mean field BCS model in which the phenomenon of mass generation is present; a rigorous proof of this equivalence is however still an open problem. In this paper we consider an interacting fermionic model in which the Cooper pairs interact through a finite range time dependent interaction. For this model (quartic in the fermions and not solvable) we are able to prove the generation of mass in the thermodynamic limit and its equivalence with the mean field BCS model. The proof is achieved by a convergent perturbation expansion about mean field theory.     

On Quasi-Exact Solvability of the Schrödinger Equation for a Free Particle on the Surface of a Spindle Torus

We show that the Schrödinger equation for a free particle on the surface of a spindle torus is quasi-exactly solvable. Our result complements former ones in an interesting way: it is known that the Schrödinger equation for a free particle on a ring torus is non-solvable, whereas it is exactly solvable for a particle on a horn torus.     

具有非局域势的量子力学模型

利用超对称性(SUSY)量子力学讨论能够精确求解的具有非局域势的量子力学模型.并表示出能够精确求解的局域势模型的一个简单非局域的表示形式,精确地得到能量本征函数和本征值.     

Solutions of nonrelativistic Schrödinger equation from relativistic Klein-Gordon equation

The relativistic one-dimensional Klein-Gordon equation can be exactly solved for a certain class of potentials. But the nonrelativistic Schrödinger equation is not necessarily solvable for the same potentials. It may be possible to obtain approximate solutions for the inexact nonrelativistic potential from the relativistic exact solutions by systematically removing relativistic portion. We search for the possibility with the harmonic oscillator potential and the Coulomb potential, both of which can be exactly solvable nonrelativistically and relativistically. Though a rigorous algebraic approach is not deduced yet, it is found that the relativistic exact solutions can be a good starting point for obtaining the nonrelativistic solutions.