News on Disconnected Diagrams *
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چکیده
We present evidence for disconnected contributions to the σπN term and the flavor singlet axial coupling g 0 A of the proton on full QCD configurations, which are obtained by means of improved stochastic estimator techniques. Furthermore we discuss results from the fermionic determination of the topological charge of the QCD vacuum (in the spirit of the Athiya-Singer theorem) again achieved with stochastic estimator methods. It turns out that this approach provides an monitor for the tunneling efficiency of the HMC on QCD with dynamical Wilson fermions which is independent on the pure gluonic method that implies cooling.
منابع مشابه
Improving Stochastic Estimator Techniques for Disconnected Diagrams ∗
Disconnected diagrams are expected to be sensitive to the inclusion of dynamical fermions. We present a feasibility study for the observation of such effects on the nucleonic matrix elements of the axial vector current, using SESAM full QCD vacuum configurations with Wilson fermions on 16 × 32 lattices, at β = 5.6. Starting from the standard methods developed by the Kentucky and Tsukuba groups,...
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For reliable comparison of the standard model prediction to the muon g−2 with its experimental value, the hadronic light-by-light scattering (HLbL) contribution must be calculated by lattice QCD simulation. HLbL contribution has many types of disconnected-type diagrams. Here, we start with recalling the point that must be taken care of in every method to calculate them by lattice QCD, and prese...
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In calculations of the hyperfine splitting in charmonium, the contributions of the disconnected diagrams is considered small and is typically ignored. We aim to estimate nonperturbatively the size of the resulting error, which could potentially affect the high precision calculations of the charmonium spectrum. Following our work on the effects of the disconnected diagrams in unquenched QCD pres...
متن کاملNeutral mesons and disconnected diagrams in Twisted Mass QCD
We evaluate properties of neutral mesons in N f = 2 dynamical simulations of TMQCD at maximal twist. The pion is explored establishing the size of the isospin splitting (an order a2 effect). We investigate the η ′ (the N f = 2 flavour singlet pseudoscalar meson) and neutral ρ and scalar mesons. We show that disconnected diagrams can be evaluated very efficiently in TMQCD using variance reductio...
متن کاملساختار فاز میدانهای پیمانه‌ای شبکه‌ای دو بعدی U(N) با کنش مختلط
We study the phase structure of two dimensional pure lattice gauge theory with a Chern term. The symmetry groups are non-Abelian, finite and disconnected sub-groups of SU(3). Since the action is imaginary it introduces a rich phase structure compared to the originally trivial two dimensional pure gauge theory. The Z3 group is the center of these groups and the result shows that if we use one ...
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تاریخ انتشار 1998