Scale-dependent mass anomalous dimension from Dirac eigenmodes

  • Anqi Cheng
  • Anna Hasenfratz
  • Gregory Petropoulos
  • David Schaich
Article

Abstract

We investigate the eigenmodes of the massless Dirac operator to extract the scale-dependent fermion mass anomalous dimension γm(μ). By combining simulations on multiple lattice volumes, and when possible several gauge couplings, we are able to measure the anomalous dimension across a wide range of energy scales. The method that we present is universal and can be applied to any lattice model of interest, including both conformal or chirally broken systems. We consider SU(3) lattice gauge theories with Nf = 4, 8 and 12 light or massless fermions. The 4-flavor model behaves as expected for a QCD-like system and demonstrates that systematic effects are manageable in practical lattice calculations. Our 12-flavor results are consistent with the existence of an infrared fixed point, at which we predict the scheme-independent mass anomalous dimension \( \gamma_m^{*}=0.32(3) \). For the 8-flavor model we observe a large anomalous dimension across a wide range of energy scales. Further investigation is required to determine whether Nf = 8 is chirally broken and walking, or if it possesses a strongly-coupled conformal fixed point.

Keywords

Lattice Gauge Field Theories Nonperturbative Effects Technicolor and Composite Models 

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Copyright information

© SISSA, Trieste, Italy 2013

Authors and Affiliations

  • Anqi Cheng
    • 1
  • Anna Hasenfratz
    • 1
  • Gregory Petropoulos
    • 1
  • David Schaich
    • 1
  1. 1.Department of PhysicsUniversity of ColoradoBoulderU.S.A

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