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Message: <blockquote data-quote="freyar" data-source="post: 6639601" data-attributes="member: 40227">Several great points in this thread to reply to --- I'm going to try to take them in related bunches.The purely 4D wormhole solutions I've perused in the last couple days require exotic matter just to exist in the first place, let alone be stable!  I haven't yet read through the 5D wormhole stuff since I'm in a busy time at work.Yes, I agree with that.  The point of the simply-connected wormhole spacetimes is that they have the local structure a multiply-connected wormhole needs.  So you can understand some basic facts about what we'd colloquially call a wormhole using a simplified model.  Think of Morris-Thorne wormholes as the spherical cows of the wormhole world.Well, if wormholes can exist at all, I don't see why a natural one could lead to multiple connections in our universe.  It's just that, like most real things, the equations are a lot messier than they are for the spherical cows.  Yeah, obviously we'd like to drill through to alpha Centauri or whereever instead. <img src="https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f609.png" class="smilie smilie--emoji" loading="lazy" width="64" height="64" alt=";)" title="Wink    ;)"  data-smilie="2"data-shortname=";)" />  But also remember that all the discussion of wormholes in the literature (at least that I've seen) is about wormholes that exist forever unchanging or else analysis of whether a wormhole that's been around forever collapses if something goes through it.  There's nothing at all about the formation of them.  (This is really quite different than the situation for black holes; I'm writing a series of papers about black hole formation myself, for example.)  Just for emphasis, the formation/creation of a wormhole isn't worked out anywhere that I've seen.  But I can make one statement: wormhole formation would change the topology of space. As Umbran says, it makes the universe multi-connected. In English, before there's as wormhole, there is one type of path from A to B; after the wormhole forms, there are two types of path, either the old type or a path through the wormhole.  This type of change is pretty problematic in general relativity --- it's hard to avoid naked singularities.  There are a few specific types of topology changes that are well-behaved in string theory, though.Next post: comments on the exotic matter required for wormholes...</blockquote>

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