Derek B. Leinweber

University of Adelaide

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Waseem Kamleh

University of Adelaide

235

Anthony G. Williams

Birmingham Women’s and Children’s NHS Foundation Trust

187

A. W. Thomas

University of Adelaide

167

R. D. Young

University of Adelaide

J. M. Zanotti

University of Adelaide

Patrick O. Bowman

University of Queensland

M. Selim Mahbub

Data61

Jia-Jun Wu

University of Adelaide

B. J. Owen

Texas Tech University

Ben Lasscock

Enthought (United States)

Cooperative Institutions

University of Adelaide

122

Thomas Jefferson National Accelerator Facility

Chinese Academy of Sciences

Institute of Modern Physics

European Organization for Nuclear Research

Deutsches Elektronen-Synchrotron DESY

University of Chinese Academy of Sciences

Fermi National Accelerator Laboratory

Massachusetts Institute of Technology

Institute of High Energy Physics

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Precision electromagnetic structure of octet baryons in the chiral regime

Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D, Particles, fields, gravitation, and cosmology (2006)

S. Boinepalli Derek B. Leinweber Anthony G. Williams J. M. Zanotti J. B. Zhang

The electromagnetic properties of the baryon octet are calculated in quenched QCD on a 20^3 x 40 lattice with a lattice spacing of 0.128 fm using the fat-link irrelevant clover (FLIC) fermion action. FLIC fermions enable simulations to be performed efficiently at quark masses as low as 300 MeV. By combining FLIC fermions with an improved-conserved vector current, we ensure that discretisation errors occur only at O(a^2) while maintaining current conservation. Magnetic moments and electric and magnetic radii are extracted from the electric and magnetic form factors for each individual quark sector. From these, the corresponding baryon properties are constructed. Our results are compared extensively with the predictions of quenched chiral perturbation theory. We detect substantial curvature and environment sensitivity of the quark contributions to electric charge radii and magnetic moments in the low quark mass region. Furthermore, our quenched QCD simulation results are in accord with the leading non-analytic behaviour of quenched chiral perturbation theory, suggesting that the sum of higher-order terms makes only a small contribution to chiral curvature.

Charge radius

Octet

10.1103/physrevd.74.093005

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Citations (110)

Center vortex evidence for a second finite-temperature QCD transition

Physical review. D/Physical review. D. (2025)

Jackson A. Mickley Chris Allton Ryan Bignell Derek B. Leinweber

Evidence for the existence of a second finite-temperature transition in quantum chromodynamics (QCD) is obtained through the study of center vortex geometry and its evolution with temperature. The dynamical anisotropic ensembles of the Fastsum Collaboration are utilized to conduct a comprehensive analysis at eight temperatures beyond the established chiral transition. Visualizations of the center vortex structure in temporal and spatial slices of the lattice reveal that vortex percolation persists through the chiral transition and ceases at a temperature that is approximately twice the chiral transition temperature Tc. This implies that confinement is retained through temperatures up to T≈2Tc, pointing toward a second transition corresponding to deconfinement. The loss of percolation is quantified by the vortex cluster extent, providing a clear signal for the deconfinement transition. Additional vortex statistics, including temporal correlations, vortex and branching point densities, the number of secondary clusters and vortex chain lengths between branching points, are scrutinized as a function of temperature. All ten measures investigated herein show the characteristics of two transitions in QCD, encompassing the chiral transition at Tc and the deconfinement transition at T≈2Tc. Performing an inflection point analysis on the vortex and branching point densities produces an estimate of Tc that agrees with the known Fastsum value. By the same procedure, a precise estimate of the deconfinement point is extracted as Td=321(6) MeV. Published by the American Physical Society 2025

10.1103/physrevd.111.034508

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Nucleon resonance structure in the finite volume of lattice QCD

Physical review. D/Physical review. D. (2017)

Jia-Jun Wu H. Kamano T.-S. H. Lee Derek B. Leinweber A. W. Thomas

An approach for relating the nucleon resonances extracted from $\ensuremath{\pi}N$ reaction data to lattice QCD calculations has been developed by using the finite-volume Hamiltonian method. Within models of $\ensuremath{\pi}N$ reactions, bare states are introduced to parametrize the intrinsic excitations of the nucleon. We show that the resonance can be related to the probability ${P}_{{N}^{*}}(E)$ of finding the bare state, ${N}^{*}$, in the $\ensuremath{\pi}N$ scattering states in infinite volume. We further demonstrate that the probability ${P}_{{N}^{*}}^{V}(E)$ of finding the same bare states in the eigenfunctions of the underlying Hamiltonian in finite volume approaches ${P}_{{N}^{*}}(E)$ as the volume increases. Our findings suggest that the comparison of ${P}_{{N}^{*}}(E)$ and ${P}_{{N}^{*}}^{V}(E)$ can be used to examine whether the nucleon resonances extracted from the $\ensuremath{\pi}N$ reaction data within the dynamical models are consistent with lattice QCD calculation. We also discuss the measurement of ${P}_{{N}^{*}}^{V}(E)$ directly from lattice QCD. The practical differences between our approach and the approach using the L\"uscher formalism to relate LQCD calculations to the nucleon resonance poles embedded in the data are also discussed.

Hamiltonian (control theory)

Eigenfunction

Lattice (music)

10.1103/physrevd.95.114507

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Citations (18)

Recent developments in quark nuclear physics

Springer eBooks (2003)

A. W. Thomas Derek B. Leinweber R. D. Young

Lattice (music)

10.1007/978-3-662-09712-0_25

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Preface

Nuclear Physics B - Proceedings Supplements (2004)

Alexander C. Kalloniatis Derek B. Leinweber Anthony G. Williams

10.1016/s0920-5632(03)02450-2

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QUENCHED CHIRAL PHYSICS IN BARYON MASSES

R. D. Young Derek B. Leinweber A. W. Thomas S. Wright

Recent work has identified that the primary differences between quenched and dynamical spectroscopy can be described by chiral loop effects.Here we highlight the features of this study.

10.1142/9789812776662_0014

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Aspects of QCD Vacuum Structure

Proceedings of The XXV International Symposium on Lattice Field Theory — PoS(LATTICE 2007) (2008)

Derek B. Leinweber Peter J. Moran

The impact of dynamical fermions on the vacuum structure of QCD is explored.Of particular interest is the topological charge correlator, q(x)q(0) , where negative values at small x reveal a sign-alternating layered structure to the topological-charge density of the QCD vacuum.We consider large 28 3 × 96 lattices from the MILC collaboration, and develop a new gluonic definition of the topological charge density, founded on a new over-improved stout-link smearing algorithm.The algorithm reproduces established results from the overlap formalism and is designed to preserve instantons.We examine the extent to which instanton-like objects are found on the lattice.Finally, we investigate the effects of dynamical sea-quark degrees of freedom on topology and find that the magnitudes of the negative dip in the q(x)q(0) correlator and the positive q(0) 2 contact term are both increased with the introduction of dynamical fermion degrees of freedom.This is in accord with expectations based on charge renormalization and the vanishing of the topological susceptibility in the chiral limit.

10.22323/1.042.0383

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Lattice gauge theory studies of the gluon propagator

arXiv (Cornell University) (1998)

Derek B. Leinweber Jon-Ivar Skullerud Anthony G. Williams

The gluon propagator in Landau gauge is calculated in quenched QCD on a large (32^3X64) lattice at beta=6.0. In order to assess finite volume and finite lattice spacing artefacts, we also calculate the propagator on a smaller volume for two different values of the lattice spacing. New structure seen in the infrared region survives conservative cuts to the lattice data, and serves to exclude a number of models that have appeared in the literature.

Propagator

Lattice (music)

Lattice gauge theory

Lattice model (finance)

10.48550/arxiv.hep-lat/9808037

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Emergent phenomena from centre vortices in dynamical QCD

Proceedings of The 39th International Symposium on Lattice Field Theory — PoS(LATTICE2022) (2022)

Waseem Kamleh James Crawford Biddle Derek B. Leinweber Adam Virgili

Quark confinement and dynamical chiral symmetry breaking are two of the most important emergent properties of the theory of quantum chromodynamics. We review recent results studying centre vortices in SU(3) lattice gauge theory with dynamical quarks. Through a vortex identification procedure, vortex-removed and vortex-only fields are obtained from the usual Monte Carlo generated gauge fields. Several comparisons between the untouched fields and the vortex-modified fields support the notion that centre vortices are fundamental to both confinement and dynamical chiral symmetry breaking in full QCD.

Color confinement

Lattice gauge theory

10.22323/1.430.0397

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Vector meson electomagnetic form factors

Ben Lasscock J. N. Hedditch Derek B. Leinweber Anthony G. Williams

Vector meson

Source

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