New classes of solutions for Euclidean scalar field theories

This paper presents new classes of exact radial solutions to the nonlinear ordinary differential equation that arises as a saddle-point condition for a Euclidean scalar field theory in $D$-dimensional spacetime. These solutions are found by exploiting the dimensional consistency of the radial differential equation for a single {\it massless} scalar field, which allows one to transform to an autonomous equation. For massive theories the radial equation is not exactly solvable but the massless solutions provide useful approximations to the results for the massive case. The solutions presented here depend on the power of the interaction and on the spatial dimension, both of which may be noninteger. Scalar equations arising in the study of conformal invariance fit into this framework and classes of new solutions are found. These solutions exhibit two distinct behaviours as $D\to2$ from above.