Partial sums and optimal shifts in shifted large-L perturbation expansions for quasi-exact potentials
| dc.creator | Znojil, Miloslav | |
| dc.date | 2004-04-27 | |
| dc.date.accessioned | 2026-07-07T05:51:45Z | |
| dc.date.available | 2026-07-07T05:51:45Z | |
| dc.description | Exact solvability (typically, of harmonic oscillators) in quantum mechanics usually implies an elementary form of the spectrum while in all the "next-to-solvable" models, the energies E are only available in an implicit form (typically, as eigenvalues of an N-dimensional matrix). We demonstrate here that certain echoes of the unattainable harmonic-oscillator ideal may still survive in the latter (often called quasi-exact) cases exemplified here by the popular sextic anharmonic oscillator. In particular we show that whenever the spatial dimension D (or, equivalently, angular momentum L) happens to be "sufficiently" large, the surprisingly compact semi-explicit energies E remain available. In detail, using the Rayleigh-Schrödinger perturbation theory in its appropriate "shifted-L" version we observe that: (1) all the k-th order approximants $E_k$ remain defined in integer arithmetics (i.e., without any errors); (2) an optimal auxiliary N-dependent shift $β(N)$ of L exists and is unique; (3) the resulting perturbative E degenerates to the series in powers of $1/[L+β(N)]^2$; (4) a certain optimal Pade re-summation formulae exist and possess a generic branched-continued-fraction structure. | |
| dc.description | 26 pages | |
| dc.identifier | https://arxiv.org/abs/physics/0404123 | |
| dc.identifier | http://arxiv.org/abs/physics/0404123 | |
| dc.identifier | Int. J. Pure Appl. Math. 12 (2004) 79-104 | |
| dc.identifier.uri | http://salesiana.dossiersoluciones.com/handle/123456789/86097 | |
| dc.subject | Computational Physics | |
| dc.title | Partial sums and optimal shifts in shifted large-L perturbation expansions for quasi-exact potentials | |
| dc.type | text |