The Stable Adjunction in $\mathbb{A}^1$-Homotopy Theory

Abstract

We prove a homotopical monadicity theorem for the adjunction between the suspension spectrum and zeroth space functors in motivic stable homotopy theory. Our proof verifies that motivic stable homotopy theory satisfies the hypotheses of the general monadicity theorem of arXiv:2607.12124. In the process, we demonstrate six preliminary results in simplicial motivic homotopy theory, the main technical ingredient being a weak commutativity theorem between the zeroth space functor and realization of simplicial motivic spectra. We also elaborate on a general framework relating monadic algebras under op-lax maps of monads. This monadic framework is used in the proof of the main results and may be of independent interest as well. These simplicial results, and the accompanying monadic framework, may provide tools toward a conjectured operadic recognition principle for motivic infinite loop spaces.