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

1991

We discuss the Ape Collaboration results for the hadronic mass spectrum obtained in the staggered fermion formulation at β =6.0 on a 24 3 × 32 lattice. We underscore the good features that are coming out at higher β values, as for example the value of the σ 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.

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.

Perfect lattice actions for staggered fermions

Nuclear Physics B, 1997

We construct a perfect lattice action for staggered fermions by blocking from the continuum. The locality, spectrum and pressure of such perfect staggered fermions are discussed. We also derive a consistent fixed point action for free gauge fields and discuss its locality as well as the resulting static quark-antiquark potential. This provides a basis for the construction of (classically) perfect lattice actions for QCD using staggered fermions.

Observations on staggered fermions at nonzero lattice spacing

Physical Review D, 2006

We show that the use of the fourth-root trick in lattice QCD with staggered fermions corresponds to a non-local theory at non-zero lattice spacing, but argue that the non-local behavior is likely to go away in the continuum limit. We give examples of this non-local behavior in the free theory, and for the case of a fixed topologically non-trivial background gauge field. In both special cases, the non-local behavior indeed disappears in the continuum limit. Our results invalidate a recent claim that at nonzero lattice spacing an additive mass renormalization is needed because of taste-symmetry breaking.