Published online by Cambridge University Press: 27 September 2021
Motivated by analogous questions in the setting of Steiner triple systems and Latin squares, Nenadov, Sudakov and Wagner [Completion and deficiency problems, Journal of Combinatorial Theory Series B, 2020] recently introduced the notion of graph deficiency. Given a global spanning property $\mathcal P$ and a graph
$G$, the deficiency
$\text{def}(G)$ of the graph
$G$ with respect to the property
$\mathcal P$ is the smallest non-negative integer t such that the join
$G*K_t$ has property
$\mathcal P$. In particular, Nenadov, Sudakov and Wagner raised the question of determining how many edges an n-vertex graph
$G$ needs to ensure
$G*K_t$ contains a
$K_r$-factor (for any fixed
$r\geq 3$). In this paper, we resolve their problem fully. We also give an analogous result that forces
$G*K_t$ to contain any fixed bipartite
$(n+t)$-vertex graph of bounded degree and small bandwidth.