Casimir multiplets suffice: strong generation in $\mathcal{N}=4$ $SU(N)$ SYM

Abstract

The Schur sector of four-dimensional $\mathcal{N}=4$ super Yang$--$Mills theory contains infinitely many protected operators, while the invariant polynomials of a single adjoint scalar are organized by finitely many Casimir degrees. I prove that the small $\mathcal{N}=4$ short multiplets built from these invariants strongly generate the associated chiral algebra, thereby establishing the $SU(N)$ case of the strong-generation conjecture of Beem et al. For every $N\ge 2$, all field components associated with degrees $2,\dots ,N$ suffice, in every conformal weight and every degree of the standard relative quantum BRST cohomology. The proof brings together cyclic trace cohomology, quantum lifting, and an arbitrary-degree quartic$--$odd transport identity. Exact field relations and a finite-rank Newton obstruction exclude every additional lowest space, including non-scalar flavor representations; the required normal-ordering corrections and BRST primitives are derived explicitly. The resulting completeness theorem explains how a finite family of supersymmetric multiplets organizes an unbounded quantum spectrum. Every Schur class is a normal polynomial in their components and derivatives, even when its gauge-theory representative involves fermions and arbitrarily many derivatives. This supplies a uniform set of local inputs for meromorphic operator products, bounds protected state multiplicities before cancellations in an index, and gives an algebraic account of the finite-rank reorganization of protected trace operators.