2005/05/10 by Shinji Mukohyama
Physics and Astronomy · #hep-th #astro-ph #gr-qc #hep-ph
published as Proceedings of the 14th Workshop on General Relativity and Gravitation (2005) · 4 pages. Talk given at JGRG 14. This complements the final version of hep-th/0502189
arxiv created 2005/05/10 · arxiv updated 2009/12/01
A tachyon is considered to be sick in the context of particle mechanics, but in field theory just indicates instability of a background. We consider a similar possibility that a ghost in field theory might be just an indication of instability of a background and that it can condense to form a different background around which there is no ghost. We construct a low energy effective field theory based on the derivative expansion around the stable background. Possible applications are discussed, including dark energy, dark matter, inflation and black hole.