Relative Calabi-Yau completions

Abstract: We generalize Keller's construction \cite{Kel11} of deformed $n$-Calabi-Yau completions to the relative context. This gives a construction that extends any given dg functor $F : A \rightarrow B$ between smooth dg categories to a dg functor $\widetilde{F} : \widetilde{A} \rightarrow \widetilde{B}$, together with a family of deformations of $(\widetilde{A},\widetilde{B},\widetilde{F})$ parametrized by relative negative cyclic homology classes $\widetilde{\eta} \in HN_{n-2}(B, A)$. We prove that these extensions admit relative $n$-Calabi-Yau structures in the sense of \cite{BD19}. In particular, this proof covers the original absolute case of \cite{Kel11}.