Self-energy and flavor interpretation of staggered fermions (original) (raw)

On the flavour interpretations of staggered fermions

Physics Letters B, 1986

The relatmnship between the flavour identifications of staggered fermions in configuration and m momentum space is clarified for interacting theorms It ~s demonstrated that these ldentlficatmn schemes are identical in the continuum hmlt.

The flavour projection of staggered fermions and the quarter-root trick

Journal of High Energy Physics, 2007

It is shown that the flavour projection of staggered fermions can be written as a projection between the fields on four separate, but parallel, lattices, where the fields on each are modified forms of the standard staggered fermion field. Because the staggered Dirac operator acts equally on each lattice, it respects this flavour projection. We show that the system can be gauged in the usual fashion and that this does not interfere with flavour projection. We also consider the path integral, showing that, prior to flavour projection, it evaluates to the same form on each lattice and that this form is equal to that used in the quarter-root trick. The flavour projection leaves a path integral for a single flavour of field on each lattice.

Revisiting symmetries of lattice fermions via spin-flavor representation

Journal of High Energy Physics, 2012

Employing the spin-flavor representation, we investigate the structures of the doubler-mixing symmetries and the mechanisms of their spontaneous breakdown in four types of lattice fermion formulation. We first revisit the U(4)×U(4) symmetries of the naive fermion with the vanishing bare mass m, and re-express them in terms of the spin-flavor representation. We apply the same method to the Wilson fermion, which possesses only the U(1) vector symmetry for general values of m. For a special value of m, however, there emerges an additional U(1) symmetry to be broken by pion condensation. We also explore two types of minimally doubled fermion, and discover a similar kind of symmetry enhancement and its spontaneous breakdown.

Revisiting symmetries of lattice fermions via spin-flavor

2016

Employing the spin-flavor representation, we investigate the structures of the doubler-mixing symmetries and the mechanisms of their spontaneous breakdown in four types of lattice fermion formulation. We first revisit the U(4)×U(4) symmetries of the naive fermion with the vanishing bare mass m, and re-express them in terms of the spin-flavor representation. We apply the same method to the Wilson fermion, which possesses only the U(1) vector symmetry for general values of m. For a special value of m, however, there emerges an additional U(1) symmetry to be broken by pion condensation. We also explore two types of minimally doubled fermion, and discover a similar kind of symmetry enhancement and its spontaneous breakdown.

Β=6.0 Staggered Quenched Fermions

Physics Letters B, 1991

We discuss the Ape Collaboration results for the hadronic mass spectrum obtained in the staggered fermion formulation at fl= 6.0 on a 243 X 32 lattice. We underscore the good features that are coming out at higher fl values, as for example the value of the a term, the status of flavor symmetry and the relation with Wilson fermion discretization.

The QCD equation of state from improved staggered fermions

2009

We calculate the equation of state in 2+1 flavor QCD at finite temperature with physical strange quark mass and almost physical light quark masses using lattices with temporal extent Ntau=8N_{\tau}=8Ntau=8. Calculations have been performed with two different improved staggered fermion actions, the asqtad and p4 actions. Overall, we find good agreement between results obtained with these two O(a2)O(a^2)O(a2) improved staggered fermion discretization schemes. A comparison with earlier calculations on coarser lattices is performed to quantify systematic errors in current studies of the equation of state. We also present results for observables that are sensitive to deconfining and chiral aspects of the QCD transition on Ntau=6N_\tau=6Ntau=6 and 8 lattices. We find that deconfinement and chiral symmetry restoration happen in the same narrow temperature interval.

12 New fermion discretizations and their applications

2016

We review the recent progress in new lattice fermion formulations. We focus on the following three types which have possibility of improving lattice simulations. (1) Flavored-mass fermions are a generalization of Wilson fermions with species-splitting mass terms. In particular, staggered-Wilson fermions initiated by Adams have possibilities of reducing numerical costs in overlap fermions and the influence of taste-breaking in staggered fermions. (2) Central-branch Wilson fermions, in which additive mass renormalization is forbidden by extra axial symmetry, could enable us to perform Wilson-fermion lattice QCD without fine-tuning. (3) Minimally doubled fermions, which reduce the number of species by species-dependent chemical potential terms, realizes a ultra-local chiral fermion at the price of hypercubic symmetry. These setups reveal unknown aspects of lattice fermions, and we obtain a deeper understanding of lattice field theory.

New fermion discretizations and their applications

Proceedings of The 30th International Symposium on Lattice Field Theory — PoS(Lattice 2012), 2012

We review the recent progress in new lattice fermion formulations. We focus on the following three types which have possibility of improving lattice simulations. (1) Flavored-mass fermions are a generalization of Wilson fermions with species-splitting mass terms. In particular, staggered-Wilson fermions initiated by Adams have possibilities of reducing numerical costs in overlap fermions and the influence of taste-breaking in staggered fermions. (2) Central-branch Wilson fermions, in which additive mass renormalization is forbidden by extra axial symmetry, could enable us to perform Wilson-fermion lattice QCD without fine-tuning. (3) Minimally doubled fermions, which reduce the number of species by species-dependent chemical potential terms, realizes a ultra-local chiral fermion at the price of hypercubic symmetry. These setups reveal unknown aspects of lattice fermions, and we obtain a deeper understanding of lattice field theory.

Theory and applications of lattice fermionic regularisations

1988

Non-perturbative lattice regularisation and the lattice definition of quantum field theories are described with emphasis on the problem of species doubling for lattice fermions. In particular, the formulation of the multi-species staggered fermions is presented. It is demonstrated that, two distinct flavour interpretations of staggered fermions are equivalent in the continuum. Using lattice fermionic regularisations, the abelian and non-abelian chiral anomalies —the quantum-induced breaking of the symmetries— are derived and their relationship with the doubling phenomenon is clarified. The extra species are generated to cancel the anomalies. To reproduce the anomalies, these doublers are given mass of the order of the cut-off. The abelian anomaly can also be recovered by identifying the lattice axial current whose associated symmetry is broken. This is illustrated in a calculation involving a current of minimal form in the coordinate-space interpretation for staggered fermions. Furt...

Lattice QCD thermodynamic results with improved staggered fermions

European Physical Journal C Particles and Fields, 2009

We present results on the QCD equation of state, obtained with two different improved dynamical staggered fermion actions and almost physical quark masses. Lattice cut-off effects are discussed in detail as results for three different lattice spacings are available now, i.e. results have been obtained on lattices with temporal extent of N τ =4,6 and 8. Furthermore we discuss the Taylor expansion approach to non-zero baryon chemical potential and present the isentropic equation of state on lines of constant entropy per baryon number.