Lazardian Witt vectors
Alexander Lai De Oliveira
TL;DR
The paper develops a choice-free framework for universal residual perfections via Lazard's universal $rac{1}{p}$-ring, introducing Lazardian Witt vectors and Lazardian jet algebras to realize a formal adjoint-equivalence structure between residual-perfection categories and perfect residue algebras. Central results include the construction of the Lazardian Witt vector functor $W^{(t)}_{m,q}$, its adjoint relationships with the residue functor $U$, and the jet-algebra adjunction $(oldsymbol{ abla},W)$, culminating in a Lazardian URP theorem that describes $A^u$ as $W(oldsymbol{ abla}(A)^{pf})$ in a canonical, choice-controlled manner. In equal characteristic, the universal residual perfection is computed explicitly as $k^{u}=( ext{HS}^m(k) ext{pf})[[oldsymbol{ ext{π}}]]/(oldsymbol{ ext{π}}^{m+1})$, connecting jet-derivation frameworks with residual perfections and extending classical Witt-vector theory to the Lazardian setting. These constructions illuminate how to canonicalize residual-perfection moduli, relate ramified Witt vectors to Lazardian structures, and integrate Hasse–Schmidt derivations into a broader, functorial Witt-vector landscape.
Abstract
We use Lazard's universal $π$-ring to construct a variation of the $π$-typical ramified Witt vector functors, which we call the Lazardian Witt vector functor. We then use the Lazardian Witt vector functor to construct the universal residual perfection of a Lazardian algebra.
