Generic dichotomy for homomorphisms for $E_0^\mathbb{N}$

TL;DR

This paper establishes a dichotomy for analytic equivalence relations involving the complex structure of $E_0^\mathbb{N}$, showing either reducibility or a form of non-reducibility characterized by factorization properties.

Contribution

It introduces a dichotomy for analytic equivalence relations with respect to $E_0^\mathbb{N}$ and proves that $E_0^\mathbb{N}$ is a prime equivalence relation, resolving a question by Clemens.

Findings

Either $E_0^{\mathbb{N}}$ reduces to $E$ or all Borel homomorphisms are essentially trivial.

$E_0^{\mathbb{N}}$ is a prime equivalence relation.

The dichotomy characterizes the complexity of analytic equivalence relations.

Abstract

We prove the following dichotomy. Given an analytic equivalence relation $E$, either ${E_0^{\mathbb{N}}}\leq_B{E}$ or else any Borel homomorphism from $E_0^{\mathbb{N}}$ to $E$ is "very far from a reduction", specifically, it factors, on a comeager set, through the projection map $(2^{\mathbb{N}})^{\mathbb{N}}\to (2^{\mathbb{N}})^k$ for some $k\in\mathbb{N}$. As a corollary, we prove that $E_0^{\mathbb{N}}$ is a prime equivalence relation, answering a question on Clemens.