Publications

Order by: publication date number of citations

• Nucleon axial form factors from lattice QCD

  Constantia Alexandrou

  SciPost Phys. Proc. 6, 006 (2022) · published 31 May 2022 | Toggle abstract · pdf

  We give an overview on the evaluation of the axial and pseudoscalar form factors of the nucleon within the lattice QCD formulation. We discuss recent results obtained from the analysisofNf =2+1+1twistedmassfermiongaugeensemblesgeneratedatphysical values of the pion mass. Besides evaluating the isovector form factors, and the PCAC and Goldberger-Treiman relations, we also discuss results for the strange and charm axial form factors. We provide a comparison with other recent lattice QCD results obtained with different discretization schemes of the fermion action.

  1 citation

• Some recent results on renormalization-group properties of quantum field theories

  Robert Shrock

  SciPost Phys. Proc. 6, 005 (2022) · published 31 May 2022 | Toggle abstract · pdf

  We discuss some higher-loop studies of renormalization-group flows and fixed points in various quantum field theories.

• Centre vortex structure of QCD-vacuum fields and confinement

  Derek Leinweber, James Biddle, Waseem Kamleh

  SciPost Phys. Proc. 6, 004 (2022) · published 31 May 2022 | Toggle abstract · pdf

  The non-trivial ground-state vacuum fields of QCD form the foundation of matter. Using modern visualisation techniques, this presentation examines the microscopic structure of these fields. Of particular interest are the centre vortices identified within the ground-state fields of lattice QCD. Our current focus is on understanding the manner in which dynamical fermions in the QCD vacuum alter the centre-vortex structure. The impact of dynamical fermions is significant and provides new insights into the role of centre vortices in underpinning both confinement and dynamical chiral symmetry breaking in QCD.

  1 citation

• The Compton Amplitude, lattice QCD and the Feynman-Hellmann approach

  K.U. Can, A. Hannaford-Gunn, R. Horsley, Y. Nakamura, H. Perlt, P.E.L. Rakow, E. Sankey, G. Schierholz, H. Stuben, R.D. Young, J.M. Zanotti

  SciPost Phys. Proc. 6, 003 (2022) · published 31 May 2022 | Toggle abstract · pdf

  A major objective of lattice QCD is the computation of hadronic matrix elements. The standard method is to use three-point and four-point correlation functions. An alternative approach, requiring only the computation of two-point correlation functions is to use the Feynman-Hellmann theorem. In this talk we develop this method up to second order in perturbation theory, in a context appropriate for lattice QCD. This encompasses the Compton Amplitude (which forms the basis for deep inelastic scattering) and hadron scattering. Some numerical results are presented showing results indicating what this approach might achieve.

• Lattice simulations of the QCD chiral transition at real $\mu_B$

  Attila Pasztor, Szabolcs Borsanyi, Zoltan Fodor, Matteo Giordano, Sandor D. Katz, Daniel Nogradi, Chik Him Wong

  SciPost Phys. Proc. 6, 002 (2022) · published 31 May 2022 | Toggle abstract · pdf

  Most lattice studies of hot and dense QCD matter rely on extrapolation from zero or imaginary chemical potentials. The ill-posedness of numerical analytic continuation puts severe limitations on the reliability of such methods. We studied the QCD chiral transition at finite real baryon density with the more direct sign reweighting approach. We simulate up to a baryochemical potential-temperature ratio of $\mu_B/T=2.7$, covering the RHIC Beam Energy Scan range, and penetrating the region where methods based on analytic continuation are unpredictive. This opens up a new window to study QCD matter at finite $\mu_B$ from first principles.

• The scalar and tensor glueball in production and decay

  Eberhard Klempt

  SciPost Phys. Proc. 6, 001 (2022) · published 31 May 2022 | Toggle abstract · pdf

  Evidence for the scalar and the tensor glueball is reported. The evidence stems from an analysis of BESIII data on radiative $J/\psi$ data into $\pi^0\pi^0$, $K_SK_S$, $\eta\eta$, and $\phi\omega$ [1]. The coupled-channel analysis is contrained by a large number of further data. The scalar intensity is described by ten scalar isoscalar mesons, covering the range from $f_0(500)$ to $f_0(2330)$. Five resonances are interpreted as mainly-singlet states in SU(3), five as mainly-octet states. The mainly-singlet resonances are produced over the full mass range, the production of octet states is limited to the 1500 to 2100 MeV mass range and shows a large peak. The peak is interpreted as scalar glueball. Its mass, width and yield are determined to $\rm M_{glueball}=(1865\pm 25)$ MeV, $\Gamma_{\rm glueball} =\rm (370\pm 50^{+30}_{-20}) MeV$, $\rm Y_{J/\psi\to \gamma G_0}=(5.8\pm1.0)\cdot 10^{-3}$. The study of the decays of the scalar mesons identifies significant glueball fractions [2]. The tensor wave shows the $f_2(1270)$ and $f_2'(1525)$ and a small enhancement at $M=2210\pm40$ MeV, $\Gamma=\rm (355^{+60}_{-30}) MeV$ [3]. An interpretation of these data is suggested.

  1 citation

• Functional renormalization group for non-Hermitian and $\mathcal{PT}$-symmetric systems

  Lukas Grunwald, Volker Meden, Dante M. Kennes

  SciPost Phys. 12, 179 (2022) · published 30 May 2022 | Toggle abstract · pdf

  We generalize the vertex expansion approach of the functional renormalization group to non-Hermitian systems. As certain anomalous expectation values might not vanish, additional terms as compared to the Hermitian case can appear in the flow equations. We investigate the merits and shortcomings of the vertex expansion for non-Hermitian systems by considering an exactly solvable $\mathcal{PT}$-symmetric non-linear toy-model and reveal, that in this model, the fidelity of the vertex expansion in a perturbatively motivated truncation schema is comparable with that of the Hermitian case. The vertex expansion appears to be a viable method for studying correlation effects in non-Hermitian systems.

  6 citations

• SPANet: Generalized permutationless set assignment for particle physics using symmetry preserving attention

  Alexander Shmakov, Michael James Fenton, Ta-Wei Ho, Shih-Chieh Hsu, Daniel Whiteson, Pierre Baldi

  SciPost Phys. 12, 178 (2022) · published 30 May 2022 | Toggle abstract · pdf

  The creation of unstable heavy particles at the Large Hadron Collider is the most direct way to address some of the deepest open questions in physics. Collisions typically produce variable-size sets of observed particles which have inherent ambiguities complicating the assignment of observed particles to the decay products of the heavy particles. Current strategies for tackling these challenges in the physics community ignore the physical symmetries of the decay products and consider all possible assignment permutations and do not scale to complex configurations. Attention based deep learning methods for sequence modelling have achieved state-of-the-art performance in natural language processing, but they lack built-in mechanisms to deal with the unique symmetries found in physical set-assignment problems. We introduce a novel method for constructing symmetry-preserving attention networks which reflect the problem's natural invariances to efficiently find assignments without evaluating all permutations. This general approach is applicable to arbitrarily complex configurations and significantly outperforms current methods, improving reconstruction efficiency between 19\% - 35\% on typical benchmark problems while decreasing inference time by two to five orders of magnitude on the most complex events, making many important and previously intractable cases tractable. A full code repository containing a general library, the specific configuration used, and a complete dataset release, are avaiable at https://github.com/Alexanders101/SPANet

  19 citations

• Critical properties of quantum three- and four-state Potts models with boundaries polarized along the transverse field

  Natalia Chepiga

  SciPost Phys. Core 5, 031 (2022) · published 30 May 2022 | Toggle abstract · pdf

  By computing the low-lying energy excitation spectra with the density matrix renormalization group algorithm we show that boundaries polarized in the direction of the transverse field lead to scale-invariant conformal towers of states at the critical point of the quantum four-state Potts model - a special symmetric case of the Ashkin-Teller model. Furthermore, by direct comparison of the excitation spectra we phenomenologically establish the duality between the transverse-polarized and three-state-mixed boundary conditions at the four-state Potts critical point. Finally, for completeness, we verify that in the quantum three-state Potts model the "new" boundary conditions dual to the mixed ones can be realized by polarizing edge spins along the transverse field.

  3 citations

• Shifts of prepotentials (with an appendix by Michele Vergne)

  Nikita Nekrasov, Nicolo Piazzalunga, Maxim Zabzine

  SciPost Phys. 12, 177 (2022) · published 27 May 2022 | Toggle abstract · pdf

  We study the dynamics of supersymmetric theories in five dimensions obtained by compactifications of M-theory on a Calabi-Yau threefold X. For a compact X, this is determined by the geometry of X, in particular the Kahler class dependence of the volume of X determines the effective couplings of vector multiplets. Rigid supersymmetry emerges in the limit of divergent volume, prompting the study of the structure of Duistermaat-Heckman formula and its generalizations for non-compact toric Kahler manifolds. Our main tool is the set of finite-difference equations obeyed by equivariant volumes and their quantum versions. We also discuss a physical application of these equations in the context of seven-dimensional gauge theories, extending and clarifying our previous results. The appendix by M. Vergne provides an alternative local proof of the shift equation.

  4 citations