A smooth non-compactly generated category

Abstract

Let $A=\mathbb{Q}[t^{\frac{1}{2^n}}:n\geq 0]$ and consider $A[u,u^{-1};σ]$, a skew Laurent polynomial ring, where $σ(t^q)=t^{2q}$. We study the kernel of derived extension of scalars along $ A[u,u^{-1};σ]\longrightarrow\mathbb{Q}[u,u^{-1}], $ the quotient by $\mathfrak{m}A[u,u^{-1};σ]$, with $\mathfrak{m}=(t^{\frac{1}{2^n}}:n\geq 0)$. A finite free resolution of $\mathfrak{m}A[u,u^{-1};σ]$ over $ A[u,u^{-1};σ]\otimes_{\mathbb{Q}} \bigl(A[u,u^{-1};σ]\bigr)^{\mathrm{op}} $ proves smoothness. A specialization inequality for matrix ranks supplies a nonzero exact colimit-preserving functor that vanishes on every compact object, proving failure of compact generation.