Milne universe, tachyons, and quantum group

Nikita A. Nekrasov

Research output: Contribution to journalArticlepeer-review

45 Citations (Scopus)


We analyze the spectrum of the bosonic and superstring on the orbifold of the space-time by a boost, leading to the cosmological singularity. We show that the modular invariance leads to the spectrum where the twisted sector tachyon, together with all other twisted sector fields, present in the Euclidean version of the orbifold, is absent. This makes it impossible to resolve the singularity by a marginal deformation of the worldsheet CFT. We also establish a relation between the resolution of rotational orbifolds in Euclidean and Lorentzian setups, and quantum groups. The analysis confirms the impossibility of resolving the cosmological orbifold singularity.

Original languageEnglish
Pages (from-to)115-124
Number of pages10
JournalSurveys in High Energy Physics
Issue number1-4
Publication statusPublished - 1 Jan 2002
Externally publishedYes


  • Milne universe
  • Orbifold
  • Quantum group
  • Tachyons


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