Spectrum of SU(2) lattice gauge theory with two adjoint Dirac flavours

TL;DR

This study uses lattice simulations to explore whether SU(2) gauge theory with two adjoint Dirac fermions exhibits conformal or near-conformal behavior in the infrared, analyzing the spectrum and phase transitions.

Contribution

The paper provides the first lattice spectrum analysis of SU(2) with two adjoint fermions and discusses potential conformal behavior and phase structure based on these results.

Findings

Indications of a transition from chiral symmetry breaking to conformal-like behavior around beta_L ~ 2.

Spectrum measurements suggest possible conformal fixed point but are not conclusive.

Comparison with fundamental fermion case highlights the complexity of confirming conformality.

Abstract

An SU(2) gauge theory with two fermions transforming under the adjoint representation of the gauge group may appear conformal or almost conformal in the infrared. We use lattice simulations to study the spectrum of this theory and present results on the masses of several gauge singlet states as a function of the physical quark mass determined through the axial Ward identity and find indications of a change from chiral symmetry breaking to a phase consistent with conformal behaviour at beta_L ~ 2. However, the measurement of the spectrum is not alone sufficient to decisively confirm the existence of conformal fixed point in this theory as we show by comparing to similar measurements with fundamental fermions. Based on the results we sketch a possible phase diagram of this lattice theory and discuss the applicability and importance of these results for the future measurement of the evolution of the coupling constant.