This might seem trivial but if I want to go about finding closed trajectories in a wormhole with a metric: $$ds^2=-dt^2+dr^2+(b^2+r^2)(d\theta^2+sin^2\theta d\phi^2)$$ how should I approach that? Is there any conditions that has to be followed? I have just started learning these, and had this doubt if they existed and if they do how to find them.I did try searching about them in net but was not able to find anything that would help me understand it better. I am familiar with finding the geodesic of this. How should I proceed from there?Any suggestion or help would be helpful.
ps:This is not my homework in case you are wondering. I am just curious to learn about these.