Chiral Symmetry Restoration in the Schwinger Model with Domain Wall Fermions

We present results on both the restoration of the spontaneously broken chiral symmetry and the effective restoration of the anomalously broken U(1)_A symmetry in finite temperature QCD at zero chemical potential using lattice QCD. We employ domain wall fermions on lattices with fixed temporal extent N_\tau = 8 and spatial extent N_\sigma = 16 in a temperature range of T = 139 - 195 MeV, corresponding to lattice spacings of a \approx 0.12 - 0.18 fm. In these calculations, we i...

We study the effective quark mass induced by the finite separation of the domain walls in the domain-wall formulation of chiral fermion as the function of the size of the fifth dimension ($L_s$), the gauge coupling ($\beta$) and the physical volume ($V$). We measure the mass by calculating the small eigenvalues of the hermitian domain-wall Dirac operator ($H_{\rm DWF}(m_0=1.8))$ in the topologically-nontrivial quenched SU(3) gauge configurations. We find that the induced quar...

A new multifermion formulation of lattice QCD is proposed. The model is free of spectrum doubling and preserves all nonanomalous chiral symmetries up to exponentially small corrections. It is argued that a small number of fermion fields may provide a good approximation making computer simulations feasible.

A different lattice fermion method is introduced. Staggered domain wall fermions are defined in 2n+1 dimensions and describe 2^n flavors of light lattice fermions with exact U(1) x U(1) chiral symmetry in 2n dimensions. As the size of the extra dimension becomes large, 2^n chiral flavors with the same chiral charge are expected to be localized on each boundary and the full SU(2^n) x SU(2^n) flavor chiral symmetry is expected to be recovered. SDWF give a different perspective ...

We describe a method to put chiral gauge theories on the lattice. Our method makes heavy use of the effective action for chiral fermions in the continuum, which is in general complex. As an example we discuss the chiral Schwinger model.

We investigate a possibility that the rough gauge problem, which have appeared to be a main reason for failures of lattice chiral gauge theories, is cured by an asymptotic-free dynamics. Taking the domain-wall model in 2(+1) dimensions with SU(2) gauge group, we carry out the quenched simulation of gauge fields in the extra dimension. By studying fermion spectra in several volumes, we show that the chiral zero modes exist on the wall without having the spontaneous symmetry br...

We report new results on the lattice regularization of the chiral Schwinger model and the chiral U(1) model in four dimensions in the CFA.

We report on studies of the chiral properties of dynamical domain wall fermions combined with the DBW2 gauge action for different gauge couplings and fermion masses. For quenched theories, the DBW2 action gives a residual chiral symmetry breaking much smaller than what was found with more traditional choices for the gauge action. Our goal is to investigate the possibilities which this and further improvements provide for the study of QCD thermodynamics and other simulations a...

We investigate a proposal for the construction of models with chiral fermions on the lattice using staggered fermions. In this approach the gauge invariance is broken by the coupling of the staggered fermions to the gauge fields. We aim at a dynamical restoration of the gauge invariance in the full quantum model. If the gauge symmetry breaking (SB) is not too severe, this procedure could lead in the continuum limit to the desired gauge invariant chiral gauge theory.

We discuss a new approach for putting gauge theories on the lattice. The gauge fields are defined on the lattice only, but are interpolated to the interior of the lattice cells, where they couple to continuum fermions. The purpose of this approach is to avoid doublers and keep the chiral symmetry of the action intact. In two dimensional models (Schwinger model and chiral Schwinger model) many results for this hybrid approach can be obtained analytically. For the vectorlike Sc...