Interactions in the IKKT matrix model on covariant quantum spacetime

Abstract: We study the interactions of the higher-spin gauge theory arising from the IKKT matrix model on a covariant quantum FLRW quantum space-time $\mathcal{M}^{1,3}_{\mathtt{J}}$, denoted as HS-IKKT. In particular, we elaborate some of the vertices and observe that they are not manifestly Lorentz invariant in the unitary formulation. We argue that Lorentz invariance of HS-IKKT can be recovered since Lorentz transformations are part of the gauge invariance in the covariant formulation. This statement is verified for some vertices with the lowest number of derivatives. The lowest-derivative sector of this theory is expected to be governed by an ``almost''-Lorentz-invariant Yang-Mills theory coupled to emergent gravity.