Wormholes connect two otherwise unrelated regions to form what is called a multiply connected space.
They present paths much quicker to travel than the paths presented by ordinary space. For example, travel from Point A to Point B in the image is greatly facilitated by the presence of the wormhole.
Wormholes may be possible on microscopic distances as a result of the quantum foam which allows particle/antiparticle pairs to leap into existence momentarily, then subsequently disappear.
Interestingly, wormholes allow travel between different times as well as different locations, so time travel may be theoretically possible.
Wormholes are commonly postulated to exist at the centers of black holes or between parallel universes with no other connections. The image below is a representation of a wormhole connecting two parallel universes.
Through the torus, the toroidal and the folding of space time...as it relates to AC...is another consideration
[link to library.thinkquest.org
In 1963, Roy Kerr devised the famous Kerr solution to Einstein's equations, a more realistic description of black holes than the original Schwarzschild solution. Kerr assumed the star that would form the black hole to be rotating and found that it would not eventually collapse to a point, but rather to a ring. When approaching the ride from the side, gravity and spacetime curvature are both still infinite, so matter is again inevitably destroyed. However, traveling through the ring would result in large but finite gravity. An object that does so and avoids being crushed by the still-formidable gravity can enter the Einstein-Rosen bridge and gain access to the mirror universe.
In 1985, cosmologist Kip Thorne was asked by science popularizer Carl Sagan to devise a hypothetical traversible wormhole. Thorne and his collaborators then created what was a remarkably simple solution that would in theory connect two periods in time. The wormhole would not rip its occupants apart, would stay open for the duration of a trip through, would not freeze its occupants inside, and would not create time paradoxes. However, it would require a never-observed form of exotic matter whose total energy is negative.
Based on this solution, Thorne later made the first scientifically sound - though not technically feasible - proposal for the design of a machine for time travel. In one version of his time machine, a chamber containing two parallel metal plates is placed on a rocket ship and accelerated to near-light velocities.
An identical chamber, with the time traveler inside, is placed on earth. The electrical field created by the plates (the Casimir effect) creates a tear in spacetime.
Since the clocks in the two chambers are ticking at different rates due to relativistic effects, the traveler is hurtled into the past or the future.
Another possible time machine involves a cylinder made of the abovementioned exotic matter. A time traveler stands inside the cylinder as the matter forms a wormhole, then rides comfortably to a distant place and time.
The mathematical reasoning of these devices is quite sound; the difficulty is in locating and exploiting exotic matter (if it even exists).
The key is a condition called averaged weak energy condition (AWEC), which must be violated for the wormhole to work.
Additionally, Stephen Hawking has declared that the wormhole entrance will emit enough radiation to make it unstable or even close it permanently.
[theoretically but not proven]