Space-Time Engineering

But this was supposed to be a conservative implementation, utilizing nothing more exotic than directed ultrarelativistic neutron stars.
Mitch Porter

This section deals with technology and science which uses the properties of ####space-time in novel ways, or actually changes the properties (like wormholes and basement universes). These technologies are naturally very speculative at present, but the scientific results below give an inkling of what may be possible.

Sections

FTL
Time Travel
Wormholes
Basement Universes
Other Sites
Books
See Also

Artificial gravity. A short description of the torus method of Robert Forward of creating (a rather weak) gravity field.
Cosmological Waveguides for gravitational waves by G. Bimonte, S. Capozziello, V. Man'ko, G. Marmo. Apparently gravitational waves can be led along waveguides of dust, which might be useful in gravity manipulation.
The gravitational wave rocket by W. B. Bonnor and M. S. Piper. In principle it ought to be possible to move a rocket using gravitational waves.

FTL - Faster Than Light Travel

Travelling faster than light is an old dream, complicated due to relativity and causality (FTL travel can cause causal loops in relativity). One way of achiving extreme speeds in general relativity is to employ suitable warps of spacetime, but the principal difficulties are severe. Another kind of solution is wormholes.

The Warp Drive: Hyper-Fast Travel Within General Relativity by Miguel Alcubierre (Class. Quantum Grav. 11 (1994), L73-L77). Demonstrates that by manipulating spacetime locally, a spaceship can move faster than light as measured by the rest of the universe.
Hyper-fast interstellar travel in general relativity by S. V. Krasnikov. A paper that demonstrates some limitations on FTL travel.
Quantum effects in the Alcubierre warp drive spacetime by William A. Hiscock. Quantum effects seems to prevent the use of the Alcubierre drive due to divergence of the stress-energy tensor as lightspeed is approached.
The unphysical nature of "Warp Drive" by Michael J. Pfenning and L.H. Ford. Another major problem with the Alcubierre drive.
Superluminal travel requires negative energies by Ken D. Olum. Superluminal travel violates the weak energy condition (like most other stuff on this page).
Faster Than Light ? by J. E. Maiorino and W. A. Rodrigues Jr. Discusses some electromagnetic field configurations that appear to move faster than light, and how they relate to the principle of relativity.
A `warp drive' with more reasonable total energy requirements by Chris Van Den Broeck A way of making the Alcubierre warp more "physical" by exploiting a movable basement universe. He has another paper, On the (im)possibility of warp bubbles, that discusses some of the objections.
Warp factor one (Robert Matthews, New Scientist 12 June 1999). Popular explanation of Chris Van Den Broecks trick to enable low-energy warp spacetimes.

Time Travel

Time travel may appear even more outrageous than FTL, but both phenomena are closely linked to each other. Causal loops (Closed Timelike Curves, CTCs) exist in some solutions to general relativity. The question is whether they can occur in physically relevant spacetimes and how paradoxes are avoided.

Time Travel for Beginners by John Gribbin.
Time machines and the Principle of Self-Consistency as a consequence of the Principle of Stationary Action (II): the Cauchy problem for a self-interacting relativistic particle. Quantum effects and the principle of minimal action may lead to a 'principle of self-consistency' ruling out time paradoxes.

Wormholes

Wormholes are shortcuts through spacetime, connecting two distant locations through a short "tunnel". They can exist in general relativity, but the main issue is whether they are traversable and possible to create.

Traversable Wormholes: Some Implications by Michael Clive Price. A very good introduction to the possibilities of wormholes.
Wormhole Warfare by Robin Hanson. A comment to the above text about the military implications of wormholes.
Wormholes in "The Alternate View" columns of John G. Cramer (Analog).

Technical Papers

Inflating Lorenzian Wormholes by Thomas A. Roman. A technical paper about the possibility of using inflation to turn a quantum wormhole macroscopic.
Can wormholes exist? by V.Khatsymovsky. Technical paper about the renormalized vacuum expectation values of electromagnetic stress-energy tensor in wormhole spacetimes. Apparently they can be stable.
Dynamic wormholes and energy conditions by Wang, A ; Letelier, P S. Non static wormholes can obey the weak and dominant energy conditions.
Bubbles and wormholes: analytic models, by Wang, A ; Letelier, P S. Discusses spacetime bubbles and how wormholes could link them.
Towards possibility of self-maintained vacuum traversible wormhole by V. Khatsymovsky
Traversable wormholes: the Roman ring by Matt Visser. Apparently chronology protection can be fooled by more complex arrangements of wormholes.
Rotating traversable wormholes by Edward Teo.
Toward a Traversable Wormhole by S. V. Krasnikov

Basement Universes

According to some theories, it is possible to spawn new universes (i.e. independent volumes of spacetime) through various means. This could be used for a variety of things, such as computation or escape from a unsuitable spacetime.

Text of `Baby Universes, Children of Blackholes' by S.W. Hawking
Baby Universes (This Week's Finds in Mathematical Physics (Week 31)) by John Baez. About the possibilities of "baby universes", and how they might be formed.
Possible Implications of the Quantum Theory of Gravity, An Introduction to the Meduso-Anthropic Principle by Louis Crane. Nontechnical paper about how the activities of technological civilizations could influence the evolution of baby universes.
The fate of black hole singularities and the parameters of the standard models of particle physics and cosmology by Lee Smolin. If baby universes can develop and the parameters of the standard model can be modified in subsequent universes, then evolution could act on entire universes.
Design for an infinitely fast computer by Alexander Chislenko. Perhaps not entirely practical, but definitely shows that very innovative designs are possible.

Other Sites

Books

C W Misner, K S Throne, and J A Wheeler, Gravitation, (Freeman) UL QC 178.M57. The classic textbook.

Robert Forward, Indistinguishable from Magic, Pocket Books; ISBN: 0671876864 1995