184 research outputs found
A Linux PC cluster for lattice QCD with exact chiral symmetry
A computational system for lattice QCD with exact chiral symmetry is
described. The platform is a home-made Linux PC cluster, built with
off-the-shelf components. At present this system constitutes of 64 nodes, with
each node consisting of one Pentium 4 processor (1.6/2.0/2.5 GHz), one Gbyte of
PC800/PC1066 RDRAM, one 40/80/120 Gbyte hard disk, and a network card. The
computationally intensive parts of our program are written in SSE2 codes. The
speed of this system is estimated to be 70 Gflops, and its price/performance is
better than $1.0/Mflops for 64-bit (double precision) computations in quenched
QCD. We discuss how to optimize its hardware and software for computing quark
propagators via the overlap Dirac operator.Comment: 24 pages, LaTeX, 2 eps figures, v2:a note and references added, the
version published in Int. J. Mod. Phys.
From insulator to quantum Hall liquid at low magnetic fields
We have performed low-temperature transport measurements on a GaAs
two-dimensional electron system at low magnetic fields. Multiple
temperature-independent points and accompanying oscillations are observed in
the longitudinal resistivity between the low-field insulator and the quantum
Hall (QH) liquid. Our results support the existence of an intermediate regime,
where the amplitudes of magneto-oscillations can be well described by
conventional Shubnikov-de Haas theory, between the low-field insulator and QH
liquid.Comment: Magneto-oscillations governed by Shubnikov-de Haas theory are
observed between the low-field insulator and quantum Hall liqui
A computational system for lattice QCD with overlap Dirac quarks
We outline the essential features of a Linux PC cluster which is now being
developed at National Taiwan University, and discuss how to optimize its
hardware and software for lattice QCD with overlap Dirac quarks. At present,
the cluster constitutes of 30 nodes, with each node consisting of one Pentium 4
processor (1.6/2.0 GHz), one Gbyte of PC800 RDRAM, one 40/80 Gbyte hard disk,
and a network card. The speed of this system is estimated to be 30 Gflops, and
its price/performance ratio is better than $1.0/Mflops for 64-bit (double
precision) computations in quenched lattice QCD with overlap Dirac quarks.Comment: 3 pages, Lattice 2002(machine
A note on Zolotarev optimal rational approximation for the overlap Dirac operator
We discuss the salient features of Zolotarev optimal rational approximation
for the inverse square root function, in particular, for its applications in
lattice QCD with overlap Dirac quark. The theoretical error bound for the
matrix-vector multiplication is derived. We check that
the error bound is always satisfied amply, for any QCD gauge configurations we
have tested. An empirical formula for the error bound is determined, together
with its numerical values (by evaluating elliptic functions) listed in Table 2
as well as plotted in Figure 3. Our results suggest that with Zolotarev
approximation to , one can practically preserve the exact
chiral symmetry of the overlap Dirac operator to very high precision, for any
gauge configurations on a finite lattice.Comment: 23 pages, 5 eps figures, v2:minor clarifications, and references
added, to appear in Phys. Rev.
Beauty mesons in lattice QCD with exact chiral symmetry
We present the first study of treating b, c, and s quarks as Dirac fermions
in lattice QCD with exact chiral symmetry. For 100 gauge configurations
generated with single-plaquette action at beta = 7.2 on the 32^3 x 60 lattice,
we compute point-to-point quark propagators for 33 quark masses in the range
0.01 < m_q a < 0.85, and measure the time-correlation function of
(pseudo-)scalar, (pseudo-)vector, and tensor mesons, for symmetric and
asymmetric quark masses respectively. The lowest-lying mass spectra of mesons
with quark contents b_bbar, c_bbar, s_bbar, and c_cbar are determined, together
with the pseudoscalar decay constants. Our results are sumarized in Tables 1-5.
Furthermore, we also determine the b and c quark masses in the MS_bar scheme,
m_b = 4.65(5) GeV, and m_c = 1.16(4) GeV.Comment: 12 page
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