<p>We consider a scalar Euclidean QFT with interaction given by a bounded, measurable function <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="220_2025_5391_Article_IEq3.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="14" /> </InlineMediaObject> <EquationSource Format="TEX">\(V\)</EquationSource> <EquationSource Format="MATHML"><math> <mi>V</mi> </math></EquationSource> </InlineEquation> such that <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="220_2025_5391_Article_IEq4.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="157" /> </InlineMediaObject> <EquationSource Format="TEX">\(V^{\pm }:=\lim _{w\rightarrow \pm \infty }V(w)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msup> <mi>V</mi> <mo>±</mo> </msup> <mo>:</mo> <mo>=</mo> <msub> <mo movablelimits="true">lim</mo> <mrow> <mi>w</mi> <mo stretchy="false">→</mo> <mo>±</mo> <mi>∞</mi> </mrow> </msub> <mi>V</mi> <mrow> <mo stretchy="false">(</mo> <mi>w</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> exist. We find a field renormalization such that all the <i>n</i>-point connected Schwinger functions for <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="220_2025_5391_Article_IEq5.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="42" /> </InlineMediaObject> <EquationSource Format="TEX">\(n\ne 2\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>n</mi> <mo>≠</mo> <mn>2</mn> </mrow> </math></EquationSource> </InlineEquation> exist non-perturbatively in the UV limit. They coincide with the tree-level one-particle irreducible Schwinger functions of the <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="220_2025_5391_Article_IEq6.gif" Format="GIF" Height="21" Rendition="HTML" Resolution="72" Type="Linedraw" Width="73" /> </InlineMediaObject> <EquationSource Format="TEX">\(\textrm{erf}(\phi /\sqrt{2})\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mtext>erf</mtext> <mo stretchy="false">(</mo> <mi>ϕ</mi> <mo stretchy="false">/</mo> <msqrt> <mn>2</mn> </msqrt> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> interaction with a coupling constant <InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="220_2025_5391_Article_IEq7.gif" Format="GIF" Height="22" Rendition="HTML" Resolution="72" Type="Linedraw" Width="89" /> </InlineMediaObject> <EquationSource Format="TEX">\(\frac{1}{2} (V^+ - V^-)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <mrow> <mo stretchy="false">(</mo> <msup> <mi>V</mi> <mo>+</mo> </msup> <mo>-</mo> <msup> <mi>V</mi> <mo>-</mo> </msup> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>. By a slight modification of our construction we can change this coupling constant to <InlineEquation ID="IEq8"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="220_2025_5391_Article_IEq8.gif" Format="GIF" Height="22" Rendition="HTML" Resolution="72" Type="Linedraw" Width="81" /> </InlineMediaObject> <EquationSource Format="TEX">\(\frac{1}{2} (V_+ - V_-)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <mrow> <mo stretchy="false">(</mo> <msub> <mi>V</mi> <mo>+</mo> </msub> <mo>-</mo> <msub> <mi>V</mi> <mo>-</mo> </msub> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>, where <InlineEquation ID="IEq9"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="220_2025_5391_Article_IEq9.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="146" /> </InlineMediaObject> <EquationSource Format="TEX">\(V_{\pm }:= \lim _{w\rightarrow 0^{\pm }} V(w)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>V</mi> <mo>±</mo> </msub> <mo>:</mo> <mo>=</mo> <msub> <mo movablelimits="true">lim</mo> <mrow> <mi>w</mi> <mo stretchy="false">→</mo> <msup> <mn>0</mn> <mo>±</mo> </msup> </mrow> </msub> <mi>V</mi> <mrow> <mo stretchy="false">(</mo> <mi>w</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>. Thereby, non-Gaussianity of these latter theories is governed by a discontinuity of <InlineEquation ID="IEq10"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="220_2025_5391_Article_IEq3.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="14" /> </InlineMediaObject> <EquationSource Format="TEX">\(V\)</EquationSource> <EquationSource Format="MATHML"><math> <mi>V</mi> </math></EquationSource> </InlineEquation> at zero. The open problem of controlling also the two-point function of these QFTs is discussed.</p>

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Exact Schwinger Functions for a Class of Bounded Interactions in \(d\ge 2\)

  • Wojciech Dybalski

摘要

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