Holographic U(1)A and string creation

Oren Bergman, Gilad Lifschytz

Research output: Contribution to journalArticlepeer-review


We analyze the resolution of the U(1)A problem in the Sakai-Sugimoto holographic dual of large Nc QCD at finite temperature. It has been shown that in the confining phase the axial symmetry is broken at order 1/Nc, in agreement with the ideas of Witten and Veneziano. We show that in the deconfined phase the axial symmetry remains unbroken to all orders in 1/Nc. In this case the breaking is due to instantons which are described by spacelike D0-branes, in agreement with 't Hooft's resolution. The holographic dual of the symmetry breaking fermion condensate is a state of spacelike strings between the D0-brane and the flavor D8-branes, which result from a spacelike version of the string creation effect. In the intermediate phase of deconfinement with broken chiral symmetry the instanton gas approximation is possibly regulated in the IR, which would imply an η′ mass-squared of order exp (-Nc).

Original languageEnglish
Article number043
JournalJournal of High Energy Physics
Issue number4
StatePublished - 1 Apr 2007


  • D-branes
  • Gauge-gravity correspondence
  • Intersecting branes models

ASJC Scopus subject areas

  • Nuclear and High Energy Physics


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