Paper detail

COH, SRT22, and multiple functionals

We prove the following result: there is a family $R = \langle R_0,R_1,\ldots \rangle$ of subsets of $ω$ such that for every stable coloring $c : [ω]^2 \to k$ hyperarithmetical in $R$ and every finite collection of Turing functionals, there is an infinite homogeneous set $H$ for $c$ such that none of the finitely many functionals map $R \oplus H$ to an infinite cohesive set for $R$. This extends the current best partial results towards the $\mathsf{SRT}^2_2$ vs. $\mathsf{COH}$ problem in reverse mathematics, and is also a partial result towards the resolution of several related problems, such as whether $\mathsf{COH}$ is omnisciently computably reducible to $\mathsf{SRT}^2_2$.