Wormholes in General Relativity
Sklar briefly touches on the notion of "wormholes", and I have noticed a good monograph on this subject by Matt Visser, Lorentzian Wormholes: from Einstein to Hawking, American Institute of Physics, 1995. Although the book itself is technical, we can have a glipse of this. In order to study this to any depth, you need to learn quantum field theory in addition to general relativity.
Reduced to its most basic elements, a Lorentzian wormhole is a short-cut through space and time. The concept of a Lorentzian wormhole is essentially synonymous with that of a spacewarp---a warping, beiding, or folding of space and possibly time. ... While we do not have any direct experimental evidence for the existence of such objects, it is commonly believed that such objects might be formed in regions of intense gravitational fields, where the highly curved nature of the spacetime manifold might allow for the existence of nontrivial topology.
Ideas along these lines have been floating around in the physics literature for the past sixty years. The earliest significant contribution I am aware of is the introduction, in 1935, of the object now referred to as an Einstein-Rosen bridge ... The field then lay fallow for twenty years until the period 1955-1957 when Wheeler coined the term "wormhole" and introduced his idea of "spacetime foam" ... A thirty year interregnum followed, punctuated by isolated contributions, until the major revival of interest following the 1988 paper by Morris and Thorn ... The last six years have been a considerable amount of activity, and the field is now sufficiently mature to warrant an overall summary being presented.
Lorentzian wormholes/spacewarp come in at least two varieties:
1. Inter-universe wormholes (wormholes that connect "our" universe with "another" universe). [see Figure 1.1]
2. Intra-universe wormholes (wormholes that connect two distant regions of our universe with each other). [See Figure 1.2] (Visser 1995, 3-4. The following figures also come from the same book.)
Last modified March 31, 2003. (c) Soshichi Uchii