Swampland (physics)

In physics, the term swampland is used in contrast to the term "landscape" to indicate physical theories or aspects of such theories that could be true if gravity were not an issue but are not compatible with string theory. Recent developments in string theory suggest that the string theory landscape of false vacua is vast.

It is natural to ask if the landscape is as vast as allowed by consistent-looking effective field theories. Some authors (e.g. Cumrun Vafa[1]) suggest that is not the case and that the landscape is surrounded by an even larger swampland of consistent-looking semiclassical effective field theories, which are actually inconsistent.

Some proposed swampland criteria[2] are the following:

  • If there is a charge symmetry, that symmetry has to be a gauge symmetry, not a global one, and in the spectrum of charged particles, there has to be at least a particle with a mass in Planck units less than the gauge coupling strength. However, not all charged particles are necessarily light.
  • That applies to magnetic monopoles as well.
  • The sign of some higher order terms in the effective action is constrained by the absence of superluminal propagation.

References

  1. ↑ Vafa, Cumrun (2005). "The String Landscape and the Swampland". arXiv:hep-th/0509212.
  2. ↑ Arkani-Hamed, Nima; Motl, Luboš; Nicolis, Alberto; Vafa, Cumrun (15 June 2007). "The String Landscape, Black Holes and Gravity as the Weakest Force". Journal of High Energy Physics. 2007 (6): 060. arXiv:hep-th/0601001. Bibcode:2007JHEP...06..060A. doi:10.1088/1126-6708/2007/06/060.


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