@article{gomez-ullateQuasiexactSolvabilityDirect2005,
 abstract = {We propose a more direct approach to constructing differential operators that preserve polynomial subspaces than the one based on considering elements of the enveloping algebra of . This approach is used here to construct new exactly solvable and quasi-exactly solvable quantum Hamiltonians on the line which are not Lie-algebraic. It is also applied to generate potentials with multiple algebraic sectors. We discuss two illustrative examples of these two applications: we show that the generalized Lamé potential possesses four algebraic sectors, and describe a quasi-exactly solvable deformation of the Morse potential which is not Lie-algebraic.},
 author = {Gómez-Ullate, D and Kamran, N and Milson, R},
 doi = {10.1088/0305-4470/38/9/011},
 file = {/Users/david/Zotero/storage/PYQNX8W8/Gómez-Ullate et al. - 2005 - Quasi-exact solvability and the direct approach to invariant subspaces.pdf},
 issn = {0305-4470, 1361-6447},
 journal = {Journal of Physics A: Mathematical and General},
 month = {March},
 number = {9},
 pages = {2005--2019},
 title = {Quasi-Exact Solvability and the Direct Approach to Invariant Subspaces},
 urldate = {2025-10-19},
 volume = {38},
 year = {2005}
}