475 research outputs found
An update on the BQCD Hybrid Monte Carlo program
We present an update of BQCD, our Hybrid Monte Carlo program for simulating
lattice QCD. BQCD is one of the main production codes of the QCDSF
collaboration and is used by CSSM and in some Japanese finite temperature and
finite density projects. Since the first publication of the code at Lattice
2010 the program has been extended in various ways. New features of the code
include: dynamical QED, action modification in order to compute matrix elements
by using Feynman-Hellman theory, more trace measurements, a more flexible
integration scheme, polynomial filtering, term-splitting for RHMC, and a
portable implementation of performance critical parts employing SIMD.Comment: Poster presented at the 35th International Symposium on Lattice Field
Theory, Granada, Spain, 18-24 June 201
Single flavour filtering for RHMC in BQCD
Filtering algorithms for two degenerate quark flavours have advanced to the
point that, in 2+1 flavour simulations, the cost of the strange quark is
significant compared with the light quarks. This makes efficient filtering
algorithms for single flavour actions highly desirable, in particular when
considering 1+1+1 flavour simulations for QED+QCD. Here we discuss methods for
filtering the RHMC algorithm that are implemented within BQCD, an open-source
Fortran program for Hybrid Monte Carlo simulations.Comment: 8 pages, 3 figures, proceedings of the 35th International Symposium
on Lattice Field Theory, 18-24 June 2017, Granada, Spai
Zeros of QCD partition function from finite density lattices
Partition function zeros steer the critical behavior of a system. Studying
four-flavor lattice QCD at finite temperature and density with the
Wilson-clover fermion action and the Iwasaki gauge action using a
phase-quenched fermion determinant, we combine statistics from multiple
chemical potentials to improve sampling of the configuration space, and aim at
unraveling the movement of zeros in finite systems. Preparing for further
investigations, we discuss methods and criteria used to sieve through complex
parameter space spanned by and , and present statistically robust zeros of the partition
function.Comment: 7 pages, 1 table, and 8 figures, presented at the 31st International
Symposium on Lattice Field Theory (Lattice 2013), 29 July - 3 August 2013,
Mainz, Germany. Changes include: fix a typo and clarify the caption for
Figure 1; clearly state estimating error for the number of independent
configuration
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