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G. Ritzenhöfer

Publications and source records attributed to G. Ritzenhöfer.

7 recordsLinked to original sources
arXiv1997

Light Quark Masses with Dynamical Wilson Fermions

We determine the masses of the light and the strange quarks in the $\bar{MS}$-scheme using our high-statistics lattice simulation of QCD with dynamical Wilson fermions. For the light quark mass we find $m^{light}_{\bar{MS}}(2 GeV) = 2.7(2) MeV$, which is lower than in quenched simulations. For the strange quark, in a sea of two dynamical light quarks, we obtain $m^{strange}_{\bar{MS}}(2 GeV) = 140(20) MeV$.

hep-lat↗
arXiv1996

Evaluating Sea Quark Contributions to Flavour-Singlet Operators in Lattice QCD

In a full QCD lattice study with $N_f = 2$ Wilson fermions, we seek to optimize the signals for the disconnected contributions to the matrix element of flavour-singlet operators between nucleon states, which are indicative for sea quark effects. We demonstrate, in form of a fluctuation analysis to the noisy estimator technique, that -- in order to achieve a tolerable signal to noise-ratio in full QCD -- it is advantageous to work with a $Z_2$-noise source rather than to rely only on gauge invariance to cancel non-gauge-invariant background. In the case of the $π$N $σ$-term, we find that 10 $Z_2$-noise sources suffice on our sample ( about 150 independent QCD configurations at $β= 5.6$ on $16^3\times32$ with $κ_{sea} = 0.157$, equivalent to $M_π/M_ρ = 0.76(1)$), to achieve decent signals and adequate fluctuations, rather than 300 such sources as recently used in quenched simulations.

hep-lat↗
arXiv1996

First Evidence of $N_f$-Dependence in the QCD Interquark Potential

We present a lattice calculation of the interquark potential between static quarks in a ``full'' QCD simulation with 2 flavours of dynamical Wilson-quarks at three intermediate sea-quark masses. We work at $β= 5.6$ on lattice size of $16^3 \times 32$ with 100 configurations per sea-quark mass. We compare the full QCD potential with its quenched counterpart at equal lattice spacing, $a^{-1} \simeq 2.0$ GeV, which is at the onset of the quenched scaling regime. We find that the full QCD potential lies consistently below that of quenched QCD. We see no evidence for string-breaking effects on these lattice volumes, $V \simeq (1.5\,\,{\rm fm})^3$.

hep-lat↗
arXiv1995

Hyper-Systolic Processing on APE100/Quadrics: N^2-Loop Computations

We investigate the performance gains from hyper-systolic implementations of n^2-loop problems on the massively parallel computer Quadrics, exploiting its 3-dimensional interprocessor connectivity. For illustration we study the communication aspects of an exact molecular dynamics simulation of n particles with Coulomb (or gravitational) interactions. We compare the interprocessor communication costs of the standard-systolic and the hyper-systolic approaches for various granularities. We predict gain factors as large as 3 on the Q4 and 8 on the QH4 and measure actual performances on these machine configurations. We conclude that it appears feasable to investigate the thermodynamics of a full gravitating n-body problem with O(10000) particles using the new method on a QH4 system.

hep-lat↗
arXiv1995

QCD with dynamical Wilson fermions - first results from SESAM

First results of a recently started simulation of full QCD with two flavours of sea-quarks at a coupling of $β= 5.6$ on a $16^3 \times 32$ lattice are presented. Emphasis is laid on the statistical significance that can be achieved by an ``integrated luminosity'' of 140 TFlop$\times$hrs, for Hybrid Monte Carlo simulations at four intermediate values of $\frac{m_π}{m_ρ}$. The simulation takes place on the Quadrics QH2 at DESY/Zeuthen and DFG/Bielefeld. The performance is optimized by means of BiCGStab and the chronological inversion method of Brower et al. We discuss the systematic errors arising from lack of the molecular dynamic's reversibility on the 32-bit QH2. For plaquette and meson correlators we find integrated autocorrelation times of $< 20$ units of molecular dynamics time and exponential autocorrelation times of about $50$ units. Using these results we perform preliminary measurements of the central potential and $π$ and $ρ$ correlators on independent configurations and obtain first estimates of the lattice spacings at three values of the dynamical hopping parameter.

hep-lat↗