Tunnel splittings for one dimensional potential wells revisited

The WKB and instanton answers for the tunnel splitting of the ground state in a symmetric double well potential are both reduced to an expression involving only the functionals of the potential, without the need for solving any auxilliary problems. This formula is applied to simple model problems. The prefactor for the splitting in the text book by Landau and Lifshitz is amended so as to apply to the ground and low lying excited states.Comment: Revtex; 1 ps figur

Application of the discrete Wentzel-Kramers-Brillouin method to spin tunneling

A discrete version of the WKB method is developed and applied to calculate the tunnel splittings between classically degenerate states of spin Hamiltonians. The results for particular model problems are in complete accord with those previously found using instanton methods. The discrete WKB method is more elementary and also yields wavefunctions.Comment: RevTex, 2ps figures, incorporates errata (typos and omitted reference) in JMP pape