Closed geodesic
= Closed geodesic
{title2=$\gamma(t+T)=\gamma(t)$}
{wiki}
A nonconstant <geodesic> whose position and tangent velocity repeat after a positive time. On a <flat torus> it is a straight line modulo the lattice, closing when its displacement is a <Euclidean lattice> vector. A primitive closed geodesic traverses its image without being an iterate of a shorter periodic geodesic.