USQCD is a collaboration of U.S. scientists developing and using large-scale computers for calculations in Lattice Quantum Chromodynamics (QCD).
For more details, please see the USQCD webpage: https://www.usqcd.org/.
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We perform numerical simulations to determine the discrete beta-function for an SU(3) system with 10 and 12 fundamental flavors using stout-smeared Moebius domain-wall fermions. Project by Anna Hasenfratz, Claudio Rebbi, Oliver Witzel.
As the number of fermion degrees of freedom in a gauge theory increases, a phase
transition is known to occur to an infrared-conformal phase lacking confinement and
chiral symmetry breaking. Uncovering the nature of this transition and the properties
of the non-trivial four-dimensional CFTs occurring inside the “conformal window” is a
long-standing and active research question in lattice gauge theory, with deep connec-
tions to composite models of new physics. We propose a set of calculations to determine
the spectrum of anomalous dimensions for SU(3) gauge theory with N f = 10 fundamen-
tal fermions, using a new method we have developed based on the gradient flow that
allows a continuous Monte Carlo Renormalization Group procedure.
This is a poster presented at the Annual ECP meeting in January, 2019. It summarizes the progress of porting Grid to GPUs.
We explore the phase structure of a four dimensional $SO(4)$ invariant lattice Higgs-Yukawa model comprising four reduced staggered fermions interacting with a real scalar field.The fermions belong to the fundamental
representation of the symmetry group while the three scalar field components transform in the self-dual representation of $SO(4)$. The model is a generalization of a four fermion system with the same
symmetries that has received recent attention because of its unusual phase structure comprising massless and massive symmetric phases separated by a very narrow phase in which a small
bilinear condensate breaking $SO(4)$ symmetry is present. The generalization described in this paper simply consists of the addition of a scalar kinetic term. We find a region of the enlarged phase diagram
which shows no sign of a fermion condensate or symmetry breaking but in which there is nevertheless evidence of a diverging correlation length. Our results in this region are consistent with the presence of
a single continuous phase transition separating the massless and massive symmetric phases observed in the earlier work.
The direct lattice calculation of hadronic tenor is helpful to the neutrino-nucleus scatterings in all the elastic, resonance and shallow inelastic scattering (SIS) regions. In this poster, we will briefly introduce the framework of calculating hadronic tenor on the lattice. Preliminary numerical results show that fine lattice spacings are crucial to our calculation.
The Nim programming language has an extensive metaprogramming capability. With the help of Nim's AST-based metaprogramming, we are building a framework where the application code is as high-level as in Python, and the low-level architecture specific code is compartmentalized. This allows us to target OpenMP, CUDA, and OpenCL for supported architectures. Here we describe our ongoing process of converting our CPU only lattice field theory framework QEX (Quantum EXpressions) as an effort of the ECP application team, and compare the performance of key math kernels with multiple backends, including OpenMP with target device offloading, CUDA, and OpenCL. We show how a LISP-like macro system in Nim, combined with its feature rich type system, helps keep us mostly at a high level, while allowing us to dig in to the performance kernels and influence the C or C++ code generated by Nim.
I present a determination of the strong coupling constant and heavy quark masses in (2+1)-flavor QCD using lattice calculations of the moments of the pseudo-scalar quarkonium correlators at several values of the heavy valence quark mass with Highly Improved Staggered Quark (HISQ) action.
I determine the strong coupling constant in MSbar scheme at four low energy scales corresponding to m, 1.5m, 2m and 3m , Nf =3, with m being the charm quark mass.
From these I obtain ΛMSbar = 301 ± 16 MeV, which is equivalent
to αs (μ = MZ , Nf = 5) = 0.1161(12).
I confirm this result with a recent determination of the strong coupling constant from the static energy using the same ensembles.