Exactly solvable models, that is, models with explicitly and completely diagonalizable
Hamiltonians are too few in number and insufficiently diverse to meet the requirements of …

We use the recently developed variational perturbation theory to continue the
renormalization constants of three-dimensional φ 4 theories to the regime of strong bare …

We study the traditional problem of convergence of perturbation expansions when the
hermiticity of the Hamiltonian is relaxed to a weaker symmetry. An elementary and quite …

Abstract The Rayleigh-Schr odinger perturbation series for the energy eigenvalue of an
anharmonic oscillator de ned by the Hamiltonian^ H (m)()=^ p2+^ x2+^ x2m with m= 2; 3; …

A recently developed renormalized strong coupling expansion [EJ Weniger, Ann. Phys.(NY)
246, 133 (1996)] is employed to compute the coefficients of the standard strong coupling …

The strongly divergent Rayleigh–Schrödinger perturbation expansion for the ground state
energy of the quartic, sextic, and octic anharmonic oscillator and a corresponding …

We develop an efficient algorithm for evaluating divergent perturbation expansions of field
theories in the bare coupling constant g B for which we possess a finite number L of …

Abstract The divergent Rayleigh-Schrödinger perturbation expansions for energy
eigenvalues of cubic, quartic, sextic and octic oscillators are summed using algebraic …

It is shown that for the one-dimensional quantum anharmonic oscillator with potential V (x)=
x 2+ g 2 x 4 the perturbation theory (PT) in powers of g 2 (weak coupling regime) and the …

With the help of variational perturbation theory we continue the renormalization constants of
φ4-theories in 4− ϵ dimensions to infinitely strong bare couplings g0 and find their power …