Moebius Fermions

A new class of domain wall fermions is defined that interpolates between Shamir's and Bori\c{c}i's form without increasing the number of Dirac applications per CG iteration. This class represents a full (real) M\"obius transformation of the Wilson kernel. Simulations on quenched Wilson lattices with $\beta = 6.0$ show that the number of lattice sites ($L_s$) in the fifth dimension can be reduced by a factor of 2 or more at fixed value of chiral symmetry violations measured by...

We present a review of the properties of generalized domain wall Fermions, based on a (real) M\"obius transformation on the Wilson overlap kernel, discussing their algorithmic efficiency, the degree of explicit chiral violations measured by the residual mass ($m_{res}$) and the Ward-Takahashi identities. The M\"obius class interpolates between Shamir's domain wall operator and Bori\c{c}i's domain wall implementation of Neuberger's overlap operator without increasing the numbe...

The M\"obius domain wall action \cite{Brower:2004xi} is a generalization of Shamir's action, which gives exactly the same overlap fermion lattice action as the separation ($L_s$) between the domain walls is taken to infinity. The performance advantages of the algorithm are presented for small ensembles of quenched, full QCD domain wall and Gap domain wall lattices \cite{Vranas:2006zk}. In particular, it is shown that at the larger lattice spacings relevant to current dynamica...

We show how the standard domain wall action can be simply modified to allow arbitrarily exact chiral symmetry at finite fifth dimensional extent. We note that the method can be used for both quenched and dynamical calculations. We test the method using smooth and thermalized gauge field configurations. We also make comparisons of the performance (cost) of the domain wall operator for spectroscopy compared to other methods such as the overlap-Dirac operator and find both metho...

We discuss two modifications of domain-wall fermions, aimed to reduce the chiral-symmetry violations presently encountered in numerical simulations.

An alternative to commonly used domain wall fermions is presented. Some rigorous bounds on the condition number of the associated linear problem are derived. On the basis of these bounds and some experimentation it is argued that domain wall fermions will in general be associated with a condition number that is of the same order of magnitude as the {\it product} of the condition number of the linear problem in the physical dimensions by the inverse bare quark mass. Thus, the ...

Critical slowing down for the Krylov Dirac solver presents a major obstacle to further advances in lattice field theory as it approaches the continuum solution. We propose a new multi-grid approach for chiral fermions, applicable to both the 5-d domain wall or 4-d Overlap operator. The central idea is to directly coarsen the 4-d Wilson kernel, giving an effective domain wall or overlap operator on each level. We provide here an explicit construction for the Shamir domain wall...

We derive the exactly conserved vector, and almost conserved axial currents for rational approximations to the overlap operator with a general Mobius kernel. The approach maintains manifest Hermiticity, and allows matrix elements of the currents to be constructed at no extra cost after solution of the usual 5d system of equations, similar to the original approach of Furman and Shamir for domain wall Fermions.

We show how the standard domain wall action can be simply modified to allow arbitrarily exact chiral symmetry at finite fifth dimensional extent $L_s$. We note that the method can be used for both quenched and dynamical calculations. We test the method using smooth and thermalized gauge field configurations. We also make comparisons of the performance (cost) of the domain wall operator for spectroscopy compared to other methods such as the overlap-Dirac operator and find both...

We proposed a construction of the Schroedinger functional scheme for the Moebius domain wall fermions (MDWF) by introducing a proper boundary operator to the original MDWF in the last conference. The spectrum of the effective four-dimensional operator was investigated. This year we investigate the fermionic contribution to the beta-function with the Moebius domain wall fermion with the SF boundary term up to the one-loop level and find that our construction properly reproduce...