Algebras over not too little discs
Damien Calaque, Victor Carmona
TL;DR
The paper develops a scale-aware formalism for observables in topological field theories by introducing $R$-truncated little discs operads $\mathsf{D}_n^R$ and proving that locally constant $\mathsf{D}_n^R$-algebras are equivalent to $\mathbb{E}_n$-algebras, thereby allowing renormalization at a fixed scale to propagate to all scales. It extends the framework to theories with defects via operads for fattened, nested, and constructible prefactorization algebras controlled by linear and corner stratifications, culminating in a generalization to defect setups and a cubical version. The paper then applies these results to quantization of constant Poisson structures, constructing Weyl-type algebras as global sections of scale-$R$ algebras (with $R=\tfrac{1}{2}$) and exploring two concrete quantization routes via Costello–Gwilliam's discretization and a discrete model, followed by a deformation-quantization program using Beilinson–Drinfeld operads. In particular, constant ($-1$)-shifted Poisson structures are quantized using BD operads, yielding BD-algebras whose cohomology recovers Weyl-type algebras, thereby connecting scale propagation with explicit quantum observables. The results provide a robust, scale-local perspective on renormalization for TFTs and offer discrete models that illustrate the interaction between topology, defects, and quantization.
Abstract
By the introduction of locally constant prefactorization algebras at a fixed scale, we show a mathematical incarnation of the fact that observables at a given scale of a topological field theory propagate to every scale over euclidean spaces. The key is that these prefactorization algebras over $\mathbb{R}^n$ are equivalent to algebras over the little $n$-disc operad. For topological field theories with defects, we get analogous results by replacing $\mathbb{R}^n$ with the spaces modelling corners $\mathbb{R}^p\times\mathbb{R}^{q}_{\geq 0}$. As a toy example in $1d$, we quantize, once more, constant Poisson structures.
