C. Arvanitis et al., CONVERGENCE OF THE OPTIMIZED DELTA-EXPANSION FOR THE CONNECTED VACUUMAMPLITUDE - ANHARMONIC-OSCILLATOR, Physical review. D. Particles and fields, 52(6), 1995, pp. 3704-3711
The convergence of the linear delta expansion for the connected genera
ting functional of the quantum anharmonic oscillator is proved. Using
an order-dependent scaling for the variational parameter lambda, we sh
ow that the expansion converges to the exact result with an error boun
ded by A exp(-cN(1/3)).