Correlation functions of $\mathrm{U}(N)$-tensor models and their Schwinger-Dyson equations

Abstract

We analyse the correlation functions of $\mathrm{U}(N)$-tensor models (or complex tensor models), which turn out to be classified by boundary graphs, and use the Ward-Takahashi identity and the graph calculus developed in [Commun. Math. Phys. (2018) 358: 589] in order to derive the complete tower of exact, analytic Schwinger-Dyson equations for correlation functions with connected boundary graphs. We write them explicitly for ranks $D=3$ and $D=4$. Throughout, we follow a non-perturbative approach to Tensor (Group) Field Theories. We propose the extension of this program to the Gurau-Witten model, a holographic tensor model based on the Sachdev-Ye-Kitaev model (SYK model).

v2. 50 pages, 7 TikZ-figures and TikZ graph theory. R. Pascalie added as co-author (see page 17). v3 coincides with v2 modulo the abstract (the breve ă in "Gur\{u}au" has been removed, to make it searchable; "graph calculus" added) and metadata-title ("coloured" replaced by the modern terminology)