Gernot Münster

Dynamical Twisted Mass Fermions with Light Quarks: Simulation and Analysis Details

In a recent paper [ETMC, P. Boucaud et al., Phys. Lett. B 650 (2007) 304, hep-lat/0701012] we presented precise lattice QCD results of our European Twisted Mass Collaboration (ETMC). They were obtained by employing two mass-degenerate flavours of twisted mass fermions at maximal twist. In the present paper we give details on our simulations and the computation of physical observables. In particular, we discuss the problem of tuning to maximal twist, the techniques we have used to compute correlators and error estimates. In addition, we provide more information on the algorithm used, the autocorrelation times and scale determination, the evaluation of disconnected contributions and the description of our data by means of chiral perturbation theory formulae.

How thick are chromo-electric flux tubes?

Abstract We analyse the space dependence of the expectation value of the chromo-electric energy density in the presence of a static quark-antiquark pair by means of the strong coupling expansion on a lattice and by the relativistic string model. Both methods indicate that the transversal width of the field energy distribution increases without bound, when the quark-antiquark separation goes to infinity.

Light Meson Physics from Maximally Twisted Mass Lattice QCD

We present a comprehensive investigation of light meson physics using maximally twisted mass fermions for Nf = 2 mass-degenerate quark flavours. By employing four values of the lattice spacing, spatial lattice extents ranging from 2.0 fm to 2.5 fm and pseudo scalar masses in the range 280 ≲ mPS ≲ 650MeV we control the major systematic effects of our calculation. This enables us to confront our Nf = 2 data with SU(2) chiral perturbation theory and extract low energy constants of the effective chiral Lagrangian and derived quantities, such as the light quark mass.

Weak-coupling expansion of the low-lying energy values in the SU(2) gauge theory on a torus☆

Abstract Relying on analytic results obtained previously, we complete the one-loop computation of the low-lying energy values of the SU(2) gauge theory in an L × L × L periodic box. The expansions are then rewritten in terms of the universal parameter z = M (0 + ) · L ( M (0 + ): energy gap in the J p = 0 + sector). We find that the crossover from small-volume to large-volume behaviour is likely to take place at z ≅ 2. Furthermore, near the crossover, the lowest energy levels (above the ground state) in the 0 + sector and the 2 + sector are practically degenerate. In each of these sectors there is one more state at about 1.5 · M (0 + ). In the 0 − sector, on the other hand, the lowest energy value is greater than 3 · M (0 + ).

Strong Coupling Expansions for the Mass Gap in Lattice Gauge Theories

Abstract We derive strong coupling expansions for the mass gap in euclidean lattice gauge theories in any space-time dimension. For gauge groups SU(2), SU(3), Z2 and Z3 the series are calculated up to order g−16. They are used to get rough estimates for the lowest glueball mass in continuum SU(2) and SU(3) gauge theories, assuming a sudden crossover from strong to weak coupling behaviour in the lattice theory.

High-temperature expansions for the free energy of vortices and the string tension in lattice gauge theories

Abstract We derive high-temperature cluster expansions for the free energy of vortices in SU(2) and Z 2 lattice gauge theories in 3 and 4 dimensions. The expected behaviour of the vortex free energy is verified. It obeys an area law behaviour. The coefficient of the area is shown to be equal to the string tension between static quarks. We calculate its expansion up to 12th order. For SU(2) in 4 dimensions the result is compared with Monte Carlo calculations of Creutz and is in good agreement at strong and intermediate coupling.

The supersymmetric Ward identities on the lattice

Abstract Supersymmetric (SUSY) Ward identities are considered for the N=1 SU(2) SUSY Yang-Mills theory discretized on the lattice with Wilson fermions (gluinos). They are used in order to compute non-perturbatively a subtracted gluino mass and the mixing coefficient of the SUSY current. The computations were performed at gauge coupling

On the phase structure of twisted mass lattice QCD

\beta=2.3

INTERFACE TENSION IN THREE-DIMENSIONAL SYSTEMS FROM FIELD THEORY

and hopping parameter

Chiral perturbation theory for lattice QCD with a twisted mass term

\kappa\!=\!0.1925