The spectral problem of an O(N) invariant decatic anharmonic oscillator in
N dimensions is considered for quasi-exactly solvable cases. The sextic anh
armonic oscillator is a special case. The eigenvalue problem is found to be
equivalent to that of an energy-dependent non-linear sl, rotor. The N depe
ndence, in the large N limit, of the ground state energies for anharmonic p
olynomial potentials of degree 2n is also considered. (C) 1999 Published by
Elsevier Science B.V. All rights reserved.