Variational basis-state expansion calculation of the mass gap in scalar field theory

We use the variational basis-state expansion method to compute the fundamental particle mass for the scalar field theory :λ(phi6-phi4) +(1/2μ2phi2: in 1+1 dimensions. The variational ansatz is a linear superposition of the known states of the scalar field theory defined by scrL0 = (1/2partial/sub μ/phipartial/sup μ/phi-1)/2 Ω2phi2, where Ω is a variational parameter. Results for the mass gap m1 are obtained, using a superposition of one- to nine-particle states of scrL0 as the variational trial states. Our results are compared to spatial-lattice calculations of the mass gap for this model