An alternative simple solution of the sextic anharmonic oscillator and perturbed Coulomb problems

Hermite function solutions of the Schrödinger equation for the sextic oscillator

We examine the conditions under which the solution of the radial stationary Schrödinger equation for the sextic anharmonic oscillator can be expanded in terms of Hermite functions. We find that this is possible for an infinite hierarchy of potentials discriminated by the parameter setting the strength of the centrifugal barrier. The $N$'th member of the hierarchy involves $N$ solutions for $N$ generally different values of the energy. For a particular member of the hierarchy, there exist infinitely many bound states with square integrable wave functions, written in terms of the Hermite functio…

A new strategy to find bound states in anharmonic oscillators

A very simple procedure to calculate eigenenergies of quantum anharmonic oscillators is presented. The method, exact but for numerical computations, consists merely in requiring the vanishing of the Wronskian of two solutions which are regular respectively at the origin and at infinity. The first one can be represented by its series expansion; for the second one, an asymptotic expansion is available. The procedure is illustrated by application to quartic and sextic oscillators.

A new general approximation scheme(NGAS) in quantum theory:application to the anharmonic- and double well oscillators

A new scheme of approximation in quantum theory is proposed which is potentially applicable to arbtrary interacting systems. The method consists in in approximating the original Hamiltonian by one corresponding to a suitable exactly solvable system (with interaction) such that the "quantum average" of both are equal, thus forcing self-consistency.The method transcends the limitations of the variational method and the perturbation theory.The results are systematically improvable by the construction of a improved perturbation theory (IPT) which automatically satisfies the condition of convergenc…

非谐振子与零模自举法

Anharmonic oscillators and the null bootstrap

本文利用微扰解析零模自举法计算六次非谐振子的能量本征值与阶梯算符至二阶，并推广到非厄米PT对称系统，验证了该方法在平移谐振子和三次非谐振子中的有效性。

Novel quasi-exactly solvable models with anharmonic singular potentials

We present new quasi-exactly solvable models with inverse quartic, sextic, octic and decatic power potentials, respectively. We solve these models exactly via the functional Bethe ansatz method. For each case, we give closed-form solutions for the energies and the wave functions as well as analytical expressions for the allowed potential parameters in terms of a set of algebraic equations.

On some conditionally solvable quantum-mechanical problems

We analyze two conditionally solvable quantum-mechanical models: a one-dimensional sextic oscillator and a perturbed Coulomb problem. Both lead to a three-term recurrence relation for the expansion coefficients. We show diagrams of the distribution of their exact eigenvalues with the addition of accurate ones from variational calculations. We discuss the symmetry of such distributions. We also comment on the wrong interpretation of the exact eigenvalues and eigenfunctions by some researchers that has led to the prediction of allowed cyclotron frequencies and field intensities.

Algebraic construction of associated functions of nondiagonalizable models with anharmonic oscillator complex interaction

A shape invariant nonseparable and nondiagonalizable two-dimensional model with anharmonic complex interaction, first studied by Cannata, Ioffe, and Nishnianidze, is re-examined with the purpose of providing an algebraic construction of the associated functions to the excited-state wavefunctions, needed to complete the basis. The two operators $A^+$ and $A^-$, coming from the shape invariant supersymmetric approach, where $A^+$ acts as a raising operator while $A^-$ annihilates all wavefunctions, are completed by introducing a novel pair of operators $B^+$ and $B^-$, where $B^-$ acts as the mi…

Quasi-exact solvability, resonances and trivial monodromy in ordinary differential equations

A correspondence between the sextic anharmonic oscillator and a pair of third-order ordinary differential equations is used to investigate the phenomenon of quasi-exact solvability for eigenvalue problems involving differential operators with order greater than two. In particular, links with Bender-Dunne polynomials and resonances between independent solutions are observed for certain second-order cases, and extended to the higher-order problems.

通过有限路径积分极限获得收敛的微扰级数：应用于各向异性振子的强耦合能量

Convergent perturbative series via finite path integral limits: application to energy at strong coupling of the anharmonic oscillator

通过有限路径积分极限获得收敛的微扰级数，应用于各向异性振子强耦合能量计算，结果在强耦合下与精确值一致。

Optimized basis expansion as an extremely accurate technique for solving time-independent Schrödinger equation

We use the optimized trigonometric finite basis method to find energy eigenvalues and eigenfunctions of the time-independent Schrodinger equation with high accuracy. We apply this method to the quartic anharmonic oscillator and the harmonic oscillator perturbed by a trigonometric anharmonic term as not exactly solvable cases and obtain the nearly exact solutions.