A counterexample to Pixton completeness in Chow
What the paper claims, in its own words
Constructs a tautological relation on a moduli space of stable pointed curves that vanishes in rational Chow, hence in rational cohomology, but lies outside Pixton's original relation span. This disproves the Chow and rational-cohomological forms of his original completeness conjecture.
The plain-language explainer for this entry is still coming.