Exact Schwinger functions for a class of bounded interactions in $d\geq 2$
Wojciech Dybalski
February 11, 2025
We consider a scalar Euclidean QFT with interaction given by a bounded,
measurable function $V$ such that $V^{\pm}:=\lim_{w\to \pm\infty}V(w)$ exist.
We find a field renormalization such that all the $n$-point connected Schwinger
functions for $n\neq 2$ exist non-perturbatively in the UV limit. They coincide
with the tree-level one-particle irreducible Schwinger functions of the
$\mathrm{erf}(\phi/\sqrt{2})$ interaction with a coupling constant $\frac{1}{2}
(V^+ - V^-)$. By a slight modification of our construction we can change this
coupling constant to $\frac{1}{2} (V_+ - V_-)$, where $V_{\pm}:= \lim_{w\to
0^{\pm}} V(w)$. Thereby non-Gaussianity of these latter theories is governed by
a discontinuity of $V$ at zero. The open problem of controlling also the
two-point function of these QFTs is discussed.
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