The generalized Tur\'{ a}n number ${ \rm ex}(G,H)$ is the maximum number of edges in an $H$-free subgraph of a graph $G.$ It is an important extension of the classical Tur\'{ a}n number ${ \rm ex}(n,H)$, which is the maximum number of edges in a graph with $n$ vertices that does not contain $H$ as a subgraph. In this paper, we consider the maximum number of edges in an even-cycle-free subgraph of the doubled Johnson graphs $J(n;k,k+1)$, which are bipartite subgraphs of hypercube graphs. We give an upper bound for ${ \rm ex}(J(n;k,k+1),C_{ 2r})$ with any fixed $k\in\mathbb{ Z}^+$ and any $n\in\mathbb{ Z}^+$ with $n\geq 2k+1.$ We also give an upper bound for ${ \rm ex}(J(2k+1;k,k+1),C_{ 2r})$ with any $k\in\mathbb{ Z}^+,$ where $J(2k+1;k,k+1)$ is known as doubled Odd graph $\widetilde{ O}_{ k+1}.$ This bound induces that the number of edges in any $C_{ 2r}$-free subgraph of $\widetilde{ O}_{ k+1}$ is $o(e(\widetilde{ O}_{ k+1}))$ for $r\geq 6,$ which also implies a Ramsey-type result.
Categories: math.CO