Abstract
Abstract The lattice phase structure of a gauge theory can be a serious obstruction to Monte Carlo studies of its continuum behaviour. This issue is particularly delicate when numerical studies are performed to determine whether a theory is in a (near-)conformal phase. In this work we investigate the heavy mass limit of the SU(2) gauge theory with N f = 2 adjoint fermions and its lattice phase diagram, showing the presence of a critical point ending a line of first order bulk phase transition. The relevant gauge observables and the low-lying spectrum are monitored in the vicinity of the critical point with very good control over different systematic effects. The scaling properties of masses and susceptibilities open the possibility that the effective theory at criticality is a scalar theory in the universality class of the four-dimensional Gaussian model. This behaviour is clearly different from what is observed for SU(2) gauge theory with two dynamical adjoint fermions, whose (near-)conformal numerical signature is hence free from strong-coupling bulk effects.
Highlights
More recent lattice studies of the theory are focused on controlling systematic effects [25,26,27,28] and on precise measurements of the anomalous dimension [29, 30]
In this work we investigate the heavy mass limit of the SU(2) gauge theory with Nf = 2 adjoint fermions and its lattice phase diagram, showing the presence of a critical point ending a line of first order bulk phase transition
The scaling properties of masses and susceptibilities open the possibility that the effective theory at criticality is a scalar theory in the universality class of the four-dimensional Gaussian model. This behaviour is clearly different from what is observed for SU(2) gauge theory with two dynamical adjoint fermions, whoseconformal numerical signature is free from strong-coupling bulk effects
Summary
In the Wilson discretisation of fermions, the lattice Dirac operator for a single fermion species of mass am (in lattice units) transforming in the representation R of the gauge group is given by. (2.5)–(2.7) show that at high bare mass the dynamical system is approximated by a gauge system with a mixed action, i.e. with an action that, in addition to the fundamental Wilson term, has a coupling to the plaquette in the representation R governed by the mass of the fermions (assumed to be large). These variant actions are known to have a non-trivial phase structure in the plane of the couplings
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