There is a paper by Alsaleh [ER=EPR] that suggests space time in connected by little worm holes. [https://inspirehep.net/literature/1496409] This might lead to a way of combining these little worm holes to create a large one by which space time travel might be possible. 

The paper is coauthored, but I think Alsaleh is the main author because he often has a characteristic way of spelling things which makes it clear to me that he was the one doing the writing.]