Hyperarithmetical Complexity of Infinitary Action Logic with Multiplexing

In 2023, Kuznetsov and Speranski introduced infinitary action logic with multiplexing $!^m\nabla \mathrm{ACT}\omega$ and proved that the derivability problem for it lies between the $\omega$ and $\omega^\omega$ levels of the hyperarithmetical hierarchy. We prove that this problem is $\Delta⁰{\omega^{\omega}$-complete} under Turing reductions. Namely, we show that it is recursively isomorphic to the satisfaction predicate for computable infinitary formulas of rank less than $\omega^\omega$ in the language of arithmetic. As a consequence we prove that the closure ordinal for $!^m\nabla \mathrm{ACT}\omega$ equals $\omega^\omega$. We also prove that the fragment of $!^m\nabla \mathrm{ACT}\omega$ where Kleene star is not allowed to be in the scope of the subexponential is $\Delta^{0_{\omega\omega}$-complete.} Finally, we present a family of logics, which are fragments of $!^m\nabla \mathrm{ACT}\omega$, such that the complexity of the $k$-th logic lies between $\Delta⁰{\omega^k}$ and $\Delta^{0_{\omega{k+1}}$.}