Instantons and chiral symmetry on the lattice

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Abstract

I address the question of how much of QCD in the chiral limit is reproduced by instantons. After reconstructing the instanton content of smoothed Monte Carlo lattice configurations, I compare hadron spectroscopy on this instanton ensemble to the spectroscopy on the original "physical" smoothed configurations using a chirally optimized clover fermion action. By studying the zero mode zone in simple instances I find that the optimized action gives a satisfactory description of it. Through the Banks-Casher formula, instantons by themselves are shown to break chiral symmetry but hadron correlators on the instanton backgrounds are strongly influenced by free quark propagation. This results in unnaturally light hadrons and a small splitting between the vector and the pseudoscalar meson channels. Superimposing a perturbative ensemble of zero momentum gauge field fluctuations (torons) on the instantons is found to be enough to eliminate the free quarks and restore the physical hadron correlators. I argue that the torons that are present only in finite volumes are probably needed to compensate the unnaturally large finite size effects due to the lack of confinement in the instanton ensemble.

Original languageEnglish
Article number034502
Pages (from-to)1-12
Number of pages12
JournalPhysical Review D - Particles, Fields, Gravitation and Cosmology
Volume62
Issue number3
Publication statusPublished - Aug 1 2000

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ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Physics and Astronomy (miscellaneous)

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