Embedding relatively hyperbolic groups into products of binary trees

We prove that if a group G is relatively hyperbolic with respect to virtually abelian peripheral subgroups then G quasiisometrically embeds into a product of binary trees. This extends the result of Buyalo, Dranishnikov and Schroeder in which they prove that a hyperbolic group quasiisometrically embeds into a product of binary trees. To prove the main result, we use the machinery of projection complexes and quasi-trees of metric spaces developed by Bestvina, Bromberg, Fujiwara and Sisto. We build on this theory by proving that one can remove certain edges from the quasi-tree of metric spaces, and be left with a tree of metric spaces which is quasiisometric to the quasi-tree of metric spaces. In particular, this reproves a result of Hume. Further, inspired by Buyalo, Dranishnikov and Schroeder's Alice's Diary, we develop a general theory of diaries and linear statistics. These notions provide a framework by which one can take a quasiisometric embedding of a metric space into a product of infinite-valence trees and upgrade it to a quasiisometric embedding into a product of binary trees.