FWD: Chronology Protection in String Theory

[KXX4493553 at aol.com]

Chronology Protection in String Theory

Authors: <A HREF="http://www.arxiv.org/find/hep-th/1/au:+Dyson_L/0/1/0/all/0/1">Lisa Dyson</A>
Comments: 17 pages. References added, typos corrected
> Many solutions of General Relativity appear to allow the possibility of 
> time travel. This was initially a fascinating discovery, but geometries of this 
> type violate causality, a basic physical law which is believed to be 
> fundamental. Although string theory is a proposed fundamental theory of quantum 
> gravity, geometries with closed timelike curves have resurfaced as solutions to 
> its low energy equations of motion. In this paper, we will study the class of 
> solutions to low energy effective supergravity theories related to the BMPV 
> black hole and the rotating Wave--D1--D5--brane system. Time travel appears to 
> be possible in these geometries. We will attempt to build the causality 
> violating regions and propose that stringy effects prohibit their construction. We 
> will show how the geometry is corrected and that, once corrected, causality 
> is preserved. We will track our chronology protection proposal in the dual 
> conformal field theory. The absence of closed timelike curves in the geometry 
> coincides with the preservation of unitarity in the conformal field theory. 
> The agent of chronology protection for the geometries studied here mirrors the 
> enhancon mechanism, a mechanism string theory employs to resolve a class of 
> naked singularities. 
http://www.arxiv.org/abs/hep-th/0302052

  kwp
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