Artan Boriçi

On the Neuberger overlap operator

Abstract We compute Neubergers overlap operator by the Lanczos algorithm applied to the Wilson–Dirac operator. Locality of the operator for quenched QCD data and its eigenvalue spectrum in an instanton background are studied.

The Deconfinement phase transition in one flavor QCD

We present a study of the deconfinement phase transition of one-flavour QCD, using the multiboson algorithm. The mass of the Wilson fermions relevant for this study is moderately large and the non-hermitian multiboson method is a superior simulation algorithm. Finite size scaling is studied on lattices of size 8 3 ×4, 12 3 ×4 and 16 3 ×4. The behaviours of the peak of the Polyakov loop susceptibility, the deconfinement ratio and the distribution of the norm of the Polyakov loop are all characteristic of a first-order phase transition for heavy quarks. As the quark mass decreases, the first-order transition gets weaker and turns into a crossover. To investigate finite size scaling on larger spatial lattices we use an effective action in the same universality class as QCD. This effective action is constructed by replacing the fermionic determinant with the Polyakov loop identified as the most relevant Z(3) symmetry breaking term. Higher-order effects are incorporated in an effective Z(3)-breaking field, h, which couples to the Polyakov loop. Finite size scaling determines the value of h where the first order transition ends. Our analysis at the end - point, hep, indicates that the effective model and thus QCD is consistent with the universality class of the

Truncated overlap fermions

Abstract In this talk I propose a new computational scheme with overlap fermions and a fast algorithm to invert the corresponding Dirac operator.

A Lanczos Approach to the Inverse Square Root of a Large and Sparse Matrix

I construct a Lanczos process on a large and sparse matrix and use the results of this iteration to compute the inverse square root of the same matrix. The algorithm is a stable version of an earlier proposal by the author. It can be used for problems related to the matrix sign and polar decomposition. The application here comes from the theory of chiral fermions on the lattice.

Truncated Overlap Fermions: the Link Between Overlap and Domain Wall Fermions

In this talk I will emphasize the role of the Truncated Overlap Fermions in showing the equivalence between the Domain Wall and Overlap Fermions up to an irrelevant factor in the fermionic integration measure. I will also show how Domain Wall type fermions with a finite number of flavors can be used to accelerate propagator calculations of their light partner in the infinite flavor limit.

Fast Methods for Computing the Neuberger Operator

I describe a Lanczos method to compute the Neuberger Operator and a multigrid algorithm for its inversion.

Chiral fermions and a multigrid algorithm

Lattice regularization of chiral fermions is an important development of the theory of elementary particles. Nontheless, brute force computer simulations are very expensive, if not prohibitive. In this letter I exploit the non-interacting character of the lattice theory in the flavor space and propose a multigrid approach for the simulation of the theory. Already a two-grid algorithm saves an order of magnitude of computer time for fermion propagator calculations.

One-flavour QCD at finite temperature☆

We present results, for heavy to moderate quark masses, of a study of thermodynamic properties of 1-flavour QCD, using the multiboson algorithm. Finite-size scaling behaviour is studied on lattices of size

Scaling in SU(3) theory with a MCRG improved lattice action

8^3\times 4

Phase structure of one-flavour QCD

,