289 research outputs found
The Role of Lattice QCD in Searches for Violations of Fundamental Symmetries and Signals for New Physics
This document is one of a series of whitepapers from the USQCD collaboration.
Here, we discuss opportunities for Lattice Quantum Chromodynamics (LQCD) in the
research frontier in fundamental symmetries and signals for new physics. LQCD,
in synergy with effective field theories and nuclear many-body studies,
provides theoretical support to ongoing and planned experimental programs in
searches for electric dipole moments of the nucleon, nuclei and atoms, decay of
the proton, - oscillations, neutrinoless double- decay
of a nucleus, conversion of muon to electron, precision measurements of weak
decays of the nucleon and of nuclei, precision isotope-shift spectroscopy, as
well as direct dark matter detection experiments using nuclear targets. This
whitepaper details the objectives of the LQCD program in the area of
Fundamental Symmetries within the USQCD collaboration, identifies priorities
that can be addressed within the next five years, and elaborates on the areas
that will likely demand a high degree of innovation in both numerical and
analytical frontiers of the LQCD research.Comment: A whitepaper by the USQCD Collaboration, 30 pages, 9 figure
Signal-to-noise improvement through neural network contour deformations for 3D lattice gauge theory
Complex contour deformations of the path integral have been demonstrated to
significantly improve the signal-to-noise ratio of observables in previous
studies of two-dimensional gauge theories with open boundary conditions. In
this work, new developments based on gauge fixing and a neural network
definition of the deformation are introduced, which enable an effective
application to theories in higher dimensions and with generic boundary
conditions. Improvements of the signal-to-noise ratio by up to three orders of
magnitude for Wilson loop measurements are shown in lattice gauge
theory in three spacetime dimensions.Comment: 9 pages, 3 figures. Proceedings for the 40th Lattice conference at
Fermilab from July 31 to August 4, 202
Multi-particle interpolating operators in quantum field theories with cubic symmetry
Numerical studies of lattice quantum field theories are conducted in finite
spatial volumes, typically with cubic symmetry in the spatial coordinates.
Motivated by these studies, this work presents a general algorithm to construct
multi-particle interpolating operators for quantum field theories with cubic
symmetry. The algorithm automates the block diagonalization required to combine
multiple operators of definite linear momentum into irreducible representations
of the appropriate little group. Examples are given for distinguishable and
indistinguishable particles including cases with both zero and non-zero spin.
An implementation of the algorithm is publicly available at
https://github.com/latticeqcdtools/mhi.Comment: 27 pages. An implementation of the algorithm is publicly available at
https://github.com/latticeqcdtools/mh
Diets high in n-3 fatty acids are associated with lower arterial stiffness in patients with rheumatoid arthritis: a latent profile analysis
Supplementation with n-3 fatty acids can influence inflammation and markers of arterial stiffness that are increased in patients with rheumatoid arthritis (RA). However, it is unknown whether specific patterns of dietary fatty acid intake are similarly associated. In a longitudinal study, eighty-six RA patients reported their dietary intake and had arterial stiffness measured using the augmentation index (AIx) at baseline and 8 months. Latent profile analysis (LPA) was performed to characterise patterns of fatty acid intake using sixteen major fatty acids. Models for two to six profiles were compared using the Akaike and Bayesian information criteria. Associations between AIx and the profiles were adjusted for age, sex, disease activity, fish oil supplementation, medications, physical activity and socio-economic status. LPA identified five distinct profiles. Profile 1 subjects (n 7) reported significantly higher intake of palmitoleic acid (16 : 1), arachidonic acid (20 : 4n-6), EPA (20 : 5n-3), DHA (22 : 6n-3) and docosapentaenoic acid (22 : 5n-3) (
Equivariant flow-based sampling for lattice gauge theory
We define a class of machine-learned flow-based sampling algorithms for
lattice gauge theories that are gauge-invariant by construction. We demonstrate
the application of this framework to U(1) gauge theory in two spacetime
dimensions, and find that near critical points in parameter space the approach
is orders of magnitude more efficient at sampling topological quantities than
more traditional sampling procedures such as Hybrid Monte Carlo and Heat Bath.Comment: 6 pages, 4 figure
First lattice QCD study of the gluonic structure of light nuclei
The role of gluons in the structure of the nucleon and light nuclei is investigated using lattice quantum chromodynamics (QCD) calculations. The first moment of the unpolarized gluon distribution is studied in nuclei up to atomic number A = 3 at quark masses corresponding to pion masses of m(pi) similar to 450 and 806 MeV. Nuclear modification of this quantity defines a gluonic analogue of the EMC effect and is constrained to be less than similar to 10% in these nuclei. This is consistent with expectations from phenomenological quark distributions and the momentum sum rule. In the deuteron, the combination of gluon distributions corresponding to the b(1) structure function is found to have a small first moment compared with the corresponding momentum fraction. The first moment of the gluon transversity structure function is also investigated in the spin-1 deuteron, where a nonzero signal is observed at m(pi) similar to 806 MeV. This is the first indication of gluon contributions to nuclear structure that can not be associated with an individual nucleon
Baryon-baryon interactions and spin-flavor symmetry from lattice quantum chromodynamics
Lattice quantum chromodynamics is used to constrain the interactions of two octet baryons at the SU(3) flavor-symmetric point, with quark masses that are heavier than those in nature (equal to that of the physical strange quark mass and corresponding to a pion mass of approximate to 806 MeV). Specifically, the S-wave scattering phase shifts of two-baryon systems at low energies are obtained with the application of Luscher\u27s formalism, mapping the energy eigenvalues of two interacting baryons in a finite volume to the two-particle scattering amplitudes below the relevant inelastic thresholds. The leading-order low-energy scattering parameters in the two-nucleon systems that were previously obtained at these quark masses are determined with a refined analysis, and the scattering parameters in two other channels containing the S and. baryons are constrained for the first time. It is found that the values of these parameters are consistent with an approximate SU(6) spin-flavor symmetry in the nuclear and hypernuclear forces that is predicted in the large-N-c limit of QCD. The two distinct SU(6)-invariant interactions between two baryons are constrained for the first time at this value of the quark masses, and their values indicate an approximate accidental SU(16) symmetry. The SU(3) irreps containing the NN(S-1(0)), NN(S-3(1)) and 1/root 2(Xi(0)n)+Xi(-)p)(S-3(1)) channels unambiguously exhibit a single bound state, while the irrep containing the Sigma(+)p(S-3(1)) channel exhibits a state that is consistent with either a bound state or a scattering state close to threshold. These results are in agreement with the previous conclusions of the NPLQCD collaboration regarding the existence of two-nucleon bound states at this value of the quark masses
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