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This Defense Intelligence Reference Document (DIA-08-1004-004), dated 6 April 2010, was produced by the Defense Intelligence Agency under its Advanced Aerospace Weapon System Applications (AAWSA) Program. It is one of a series of advanced technology reports from FY 2009. It reviews the general relativity physics of traversable wormholes and flat-faced "stargate" solutions for faster-than-light travel. It also covers the exotic negative energy these would need, proposed lab methods for generating it such as the Casimir effect and squeezed vacuum, and the constraints involved.
UNCLASSIFIED/;SflHl 8FFHil.t.k Wfili IH.k\f II. A Brief Review of Transversable Wormholes and the Stargate Solution How does one study the physics of FTL spacetimes within the framework of general relativity theory? When studying spacetime physics, the normal philosophy is to take the general relativistic field equation, add some form of matter, make simplifying assumptions, and then solve to deduce what the geometry of spacetime will be. 1 This is very difficult to do because there are ten nonlinear second-order partial differential equations with four redundancies (arbitrary choice of spacetime coordinates) and four constraints (stress-energy conservation). There is a tremendous body of research that takes exactly this approach, either analytically or numerically. However, this is not the best strategy for understanding wormhole spacetimes. The appropriate strategy is to decide beforehand on a definition of the traversable wormhole that you desire and decide what the spacetime geometry should look like. Given the desired geometry, use the general relativistic field equation to calculate the distribution of matter required to set up this geometry. Then one needs to assess whether the required distribution of matter is physically reasonable and whether it violates any basic rules of physics, etc. The following sections briefly outline the key results for traversable wormholes. A. TRAVERSABLE WORMHOLES Traversable wormholes represent a class of exact metric solutions of the general relativistic field equation. The solutions are "exact" in the sense that no approximations requiring a plethora of physical assumptions have to be made to derive the appropriate spacetime geometry. To define a stable traversable wormhole one needs to define the desirable physical requirements it is to have in order to achieve the desired FTL travel benefit. The desired requirements are the following (Reference 1, 3): • Travel time through the wormhole tunnel or throat should bes; 1 year as seen by both the travelers and outside static observers. • Proper time as measured by travelers should not be dilated by relativistic effects. • The gravitational acceleration and tidal-gravity accelerations between different parts of the travelers' body should be s; 1 go (go is the acceleration of gravity near the Earth's surface, 9.81 m/s2) when going through the wormhole. • Travel speed through the tunnel/throat should be < c. • Travelers (made of ordinary matter) must not couple strongly to the material that generates the wormhole curvature; the wormhole must be threaded by a vacuum tube through which the travelers can move. • There is no event horizon at the wormhole throat. 1 The Einstein field equation is: G,,, =R, .. - [(1/2) g,,. R] = -(811G/c4)'f;,., where G,,, is the Einstein curvature tensor, Rp, Is the Ricci curvature tensor, R - R",, (the trace of R,,.) is the Ricci scalar curvature, T,,, is the stress-energy- rnornenturn tensor (a matrix quantity that encodes the density and flux of a matter source's energy and momentum), G is Newton's universal gravitation constant (6.673 x 10-11 Nm'/kg7), and c is the speed of light. In simplest terms, this relation states that gravity is a manifestation of the spacetime curvature (G,.,) induced by a source of matter (T,.. ,). The Greek indices (11, v = 0 3) denote spacetime coordinates, xa .. x1, such that x, __ x, = space coordinates and xo - time coordinate. 1 UNCLASSIFIED/ ;'F8R: 8FFI81.t.k Wliilii &Hbl:f
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