Two-step Multi-boson Algorithm Research Articles

The low-lying mass spectrum of the N = 1 SU(2) SUSY Yang-Mills theory with Wilson fermions

We analyze the low energy spectrum of bound states of the N = 1 SU(2) SUSY Yang-Mills Theory (SYM). This work continues the investigation of the non-perturbative properties of SYM by Monte Carlo simulations in the Wilson discretization with dynamical gluinos. The dynamics of the gluinos is included by the Two-Step Multi-Bosonic Algorithm (TSMB) for dynamical fermions. A new set of configurations has been generated on a \(16^3\cdot 32\) lattice at \(\beta = 2.3\) and \(\kappa = 0.194\). The analysis also includes sets of configurations previously generated on a smaller (\(12^3\cdot 24\)) lattice at \(\kappa = 0.1925, 0.194\) and 0.1955. Guided by predictions from low energy Lagrangians, we consider spin-1/2, scalar and pseudoscalar particles. The spectrum of SYM is a challenging subject of investigation because of the extremely noisy correlators. In particular, meson-like correlators contain disconnected contributions. The larger time-extension of the \(16^3\cdot 32\) lattice allows to observe two-state signals in the effective mass. Finite-volume effects are monitored by comparing results from the two lattice sizes.

Two Algorithms and Lattice U(1) Model

Two algorithms in the dynamical fermions approach, the hybrid Monte Carlo method and the two-step multiboson algorithm, are tested in case of the Wilson U(1) model on a four-dimensional lattice. Relations for the parameters and for the performance values of the algorithms are proposed. A comparison of the algorithms by the correlation functions evaluated and by the efficiency is carried out, and a conclusion about the suitability of the algorithms for studies of the lattice U(1) model is given.

Performance studies of the two-step multiboson algorithm in compact lattice QED

The performance of the two-step multiboson (TSMB) algorithm is investigated in comparison with the hybrid Monte Carlo (HMC) method for compact lattice QED with standard Wilson fermions both in the Coulomb and confinement phases. The restriction to QED allows for extensive measurements of autocorrelation times. Preliminary results show that the TSMB algorithm is at least competitive with standard HMC.

Dynamical fermion algorithm for variable actions

A new version of the two-step multi-boson algorithm is developed with different fermion actions in the multi-boson and noisy Metropolis steps.

Numerical study of dense adjoint 2-color matter

We study the global symmetries of SU(2) gauge theory with N flavors of staggered fermions in the presence of a chemical potential. We motivate the special interest of the case N = 1 (staggered) with fermions in the adjoint representation of the gauge group. We present results from numerical simulations with both hybrid Monte Carlo and the Two-Step Multi-Bosonic algorithm.

Simulation of QCD and other similar theories

In QCD one can change the representation of the gauge group for quarks and/or the gauge group itself. Examples of such generalizations are: (a) supersymmetric Yang-Mills theory with gauge group SU(2) or SU(3); (b) QCD with SU(2) colour and quarks in the adjoint representation; (c) QCD with three equal-mass quarks. Experience and perspectives in simulations of these theories by applying the two-step multi-bosonic algorithm is described. As an example of an interesting physical problem in these theories the expected spontaneous CP-violation in QCD with three equal-mass quarks is discussed.

Numerical simulation of dynamical gluinos: experience with a multi-bosonic algorithm and first results

We report on our experience with the two-step multi-bosonic algorithm in a large scale Monte Carlo simulation of the SU(2) Yang-Mills theory with dynamical gluinos. First results are described on the low lying spectrum of bound states, the string tension and the gluino condensate.