Recent content by HarryRool

You're right. A wormhole connection between two location in a 3-sphere universe has the topology of a torus. We do not, however, want to define a wormhole as a space with the topology of a torus. Were we to do that, a connection between to two universes (two distinct 3-spheres) -- that is...

"The spatial part of the wormhole is an ordinary chunk of 3-space." No. "Nontrivial topology" essentially means that the space contains a hole (whose boundary is ∂Σ). "So I think this is just saying that the boundary of the wormhole is a sphere." Not quite. It's saying the boundary has the...

Be aware that Visser is assuming a wormhole metric (gravitational field) that is discontinuous across an infinitesimally thin throat. This assumption naturally leads to a nonconservative gravitational field, which motivates his calculation. But the usual assumption in general relativity, as I...

Even if you assume that the wormholes are somehow stable, your scheme will still fail. The reason has to do with what happens inside the wormhole. [A portal-like wormhole is infinitesimally thin. So you assume that there is no "inside" (a finite region that objects would traverse). But there...

@RocketSci5KN: "...any additional bizarre questions about the nature of these imaginary things seems like a waste of time to me..." You're not thinking like physicists do. It is exceedingly productive to ponder areas of your physical theories that seem to lead to contradictions or make...

A) If a black hole travels into a wormhole would it collapse the wormhole? Short answer: Generally, yes. Longer answer: Depends on the mass of the black hole relative to that of the wormhole. It also depends on the so-called equation of state of the exotic matter that sustains the wormhole...

Seriously, HuaMin, Google is your friend. There are also quite a few books on wormholes intended for lay audiences: Cosmic Wormholes by Paul Halpern Black Holes & Time Warps -- Einsteins Outrageous Legacy by Kip Thorne Black Holes, Wormholes and Time Machines by Jim Al-Khalili The...

Yes. A semiclassical calculation is of course understood to be unreliable at the Planck scale. However, to whatever extent and in whatever regime it might be reliable, the calculation's result that seems to indicate the destruction or non-traversability of time-machine configured wormholes...

Check out section 23.3 in Visser's Lorentzian Wormholes -- From Einstein to Hawking . The reference in the scientific literarature (for Thomas Roman being the first to realize that wormholes permit time travel) actually points to a popular reference by Kip Thorne. In "Traversable...

Faster Than Light -- Superluminal Loop Holes in Physics by Nick Herbert

Thomas Roman seems to have been the first to realize that wormholes can be used to create time machines. His argument involved 2 wormholes. This avoids the wormhole-destroying feedback loop that you alluded to. The trick is that with two wormholes, you can have a time machine without...

Bracketed insertions mine. The frequency shift of light from galaxy A could range from being extremely red, to zero, to extremely blue. It depends on the motion of the wormhole mouths. A course, light from galaxy B would have the usual Hubble redshift. Suppose that the wormhole mouth near...

I looked at the Visser book once. If you're not at least a graduate student in physics with advanced calculus and differential geometry under your belt, you probably don't have much of a chance of understanding it. It's way over my head at least. Also, it's like 16 years old. I think that...

You might want to check out this Wormhole FAQ. Actually, the term "Einstein-Rosen bridge" is not synonymous with "wormhole". An Einstein-Rosen bridge is a particular type of wormhole. It is the non-traversable so-called maximally extended Schwarzschild solution to the Einstein equations...

String theory has nothing specific to say about information loss. Preservation of information ("unitary evolution" from initial conditions) is basic to quantum theory. Information loss through a wormhole is not a concern, because the location of the "lost" information is perfectly clear...