Study of the change from walking to non-walking behavior in a vectorial gauge theory as a function of N_f

We study a vectorial gauge theory with gauge group SU(N_c) and a variable number, N_f, of massless fermions in the fundamental representation of this group. Using approximate solutions of Schwinger-Dyson and Bethe-Salpeter equations, we calculate meson masses and investigate how these depend on N_f. We focus on the range of N_f extending from near the boundary with a non-Abelian Coulomb phase, where the theory exhibits a slowly running ("walking") gauge coupling, toward smaller values where the theory has non-walking behavior. Our results include determinations of the masses of the lowest-lying flavor-adjoint mesons with J^PC = 0 ^-+, 1^-, 0⁺⁺, and 1⁺⁺ (the generalized π, ρ, a₀, and a₁). Related results are given for flavor-singlet mesons and for the generalization of f_π. These results give insight into the change from walking to non-walking behavior in a gauge theory, as a function of N_f.