科研之友
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摘要
The quantization of gauge theories usually proceeds through the introduction of ghost fields and Becchi-Rouet-Stora-Tyutin (BRST) symmetry. In the case of quantum gravity in the presence of boundaries, the BRST-invariant boundary value problem for the gauge field operators is nonelliptic, and consequently the definition of the effective action using heat-kernel techniques becomes problematic. This paper examines general classes of BRST-invariant boundary conditions and presents new boundary conditions for quantum gravity that fix the extrinsic curvature on the boundary and lead to a well-defined effective action. This prompts a discussion of the wider issue of nonellipticity in BRST-invariant boundary value problems and when the use of gauge-fixing terms on the boundary can resolve the issue.
- 出版日期2013-11-26
