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C. Gebert

Publications and source records attributed to C. Gebert.

13 recordsLinked to original sources
arXiv2003

Quark mass dependence of pseudoscalar masses and decay constants

The dependence of pseudo-scalar masses and decay constants on the sea and valence quark masses is investigated in the pseudo-Goldstone boson sector of QCD with two light quark flavours. The sea quark masses are at present in the range ${1/3}m_s \leq m_{ud} \leq {2/3}m_s$ whereas the valence quark masses satisfy ${1/2}m_{sea} \leq m_{val} \leq 2m_{sea}$. The values of the Gasser-Leutwyler low energy constants $L_4$, $L_5$, $L_6$ and $L_8$ are estimated. The computation is done with the Wilson-quark lattice action at gauge coupling $β=5.1$ on $16^4$ lattices. ${\cal O}(a)$ effects are taken into account by applying chiral perturbation theory for the Wilson lattice action as proposed by Rupak and Shoresh.

hep-lat↗
arXiv2003

Partially quenched chiral perturbation theory and numerical simulations

The dependence of the pseudoscalar meson mass and decay constant is compared to one-loop Partially Quenched Chiral Perturbation Theory (PQChPT) in a numerical simulation with two light dynamical quarks. The characteristic behaviour with chiral logarithms is observed. The values of the fitted PQChPT-parameters are in a range close to the expectation in continuum in spite of the fact that the lattice spacing is still large, namely a=0.28 fm.

hep-lat↗
arXiv2003

A recurrence scheme for least-square optimized polynomials

A recurrence scheme is defined for the numerical determination of high degree polynomial approximations to functions as, for instance, inverse powers near zero. As an example, polynomials needed in the two-step multi-boson (TSMB) algorithm for fermion simulations are considered. For the polynomials needed in TSMB a code in C is provided which is easily applicable to polynomial degrees of several thousands.

hep-lat↗
arXiv2002

Lattice QCD with light dynamical quarks

We report on the simulation of QCD with light dynamical quarks using the two-step multi-boson (TSMB) algorithm. In an exploratory study with two flavours of quarks at lattice spacing about 0.27 fm and with quark mass down to one sixth of the strange quark mass eigenvalue spectra and autocorrelations have been studied. Here we present results on the volume dependence as well as tests of possible algorithmic improvements.

hep-lat↗
arXiv2002

On the price of light quarks

The computational cost of numerical simulations of QCD with light dynamical Wilson-quarks is estimated. The qualitative behaviour of the pion mass and coupling at small quark masses is discussed.

hep-lat↗
arXiv2002

Numerical simulation tests with light dynamical quarks

Two degenerate flavours of quarks are simulated with small masses down to about one fifth of the strange quark mass by using the two-step multi-boson (TSMB) algorithm. The lattice size is 8^3 x 16 with lattice spacing about 0.27fm which is not far from the N_t=4 thermodynamical cross-over line. Autocorrelations of different physical quantities are estimated as a function of the quark mass. The eigenvalue spectra of the Wilson-Dirac operator are investigated.

hep-lat↗
arXiv2002

Unquenched domain wall quarks with TSMB

The numerical simulation of domain wall quarks with the two-step multi-boson (TSMB) algorithm is investigated. Tests are performed on a 8^3*4 lattice with N_f=2 quark flavours.

hep-lat↗
arXiv2002

The supersymmetric Ward identities on the lattice

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 $β$=2.3 and hopping parameter $κ$=0.1925, 0.194, 0.1955 using the two-step multi-bosonic dynamical-fermion algorithm. Our results are consistent with a scenario where the Ward identities are satisfied up to O(a) effects. The vanishing of the gluino mass occurs at a value of the hopping parameter which is not fully consistent with the estimate based on the chiral phase transition. This suggests that, although SUSY restoration appears to occur close to the continuum limit of the lattice theory, the results are still affected by significant systematic effects.

hep-lat↗
arXiv2001

Lattice supersymmetric Ward identities

SUSY Ward identities for the N=1 SU(2) SUSY Yang-Mills theory are studied on the lattice in a non-perturbative numerical approach. As a result a determination of the subtracted gluino mass is obtained.

hep-lat↗
arXiv2001

The Quest for Light Sea Quarks: Algorithms for the Future

As part of a systematic algorithm study, we present first results on a performance comparison between a multibosonic algorithm and the hybrid Monte Carlo algorithm as employed by the SESAM collaboration. The standard Wilson fermion action is used on 32*16^3 lattices at beta=5.5.

hep-lat↗
arXiv2000

SUSY Ward identities in N=1 SYM theory on the lattice

The SUSY Ward identities (WIs) for the N=1 SU(2) SUSY Yang Mills theory discretized on the lattice with Wilson fermions (gluinos) are considered. The study is performed in the framework of a Monte Carlo simulation of the model with light dynamical gluinos. The renormalization and mixing constants of the lattice SUSY current $Z_S$ and $Z_T$ and the additively renormalized gluino mass $m_S$ are unknown parameters of the SUSY WIs. Using suitable on-shell combinations of the WIs, the ratios $Z_T/Z_S$ and $m_S/Z_S$ are determined non-perturbatively at one value of the coupling constant $g_0$ and two values of the hopping parameter $κ$.

hep-lat↗