# Solution of the self-dual $\Phi^4$ QFT-model on four-dimensional Moyal space

## TL;DR

This paper provides an exact solution to the planar sector of the self-dual $\

## Contribution

It solves the Fredholm equation for the model using hypergeometric functions, completing the planar sector construction and analyzing spectral dimension.

## Key findings

- Spectral dimension drops below 4 for certain coupling constants.
- Explicit hypergeometric function solution for the Fredholm equation.
- Power series approximation of the solution to all orders in coupling.

## Abstract

Previously the exact solution of the planar sector of the self-dual $\Phi^4$-model on 4-dimensional Moyal space was established up to the solution of a Fredholm integral equation. This paper solves, for any coupling constant $\lambda>-\frac{1}{\pi}$, the Fredholm equation in terms of a hypergeometric function and thus completes the construction of the planar sector of the model. We prove that the interacting model has spectral dimension $4-2\frac{\arcsin(\lambda\pi)}{\pi}$ for $|\lambda|<\frac{1}{\pi}$. It is this dimension drop which for $\lambda>0$ avoids the triviality problem of the matricial $\Phi^4_4$-model. We also establish the power series approximation of the Fredholm solution to all orders in $\lambda$. The appearing functions are hyperlogarithms defined by iterated integrals, here of alternating letters $0$ and $-1$. We identify the renormalisation parameter which gives the same normalisation as the ribbon graph expansion.