Synchronous fellow-traveller property
= Synchronous fellow-traveller property
Two <paths> satisfy the synchronous fellow-traveller property with constant $K$ if $d(p(t),q(t))\le K$ for all equal times, with completed <paths> held at their endpoints. Checking integer times suffices up to increasing $K$ by at most two for unit-speed edge <paths>. A synchronous <combing of a group> requires a uniform constant for all adjacent endpoints.