Tue·Nov 9, 2021Tuesday·November 9, 2021

1. 01*

   Gauge-invariant renormalization of fermion bilinears and energy-momentum tensor on the lattice

   G. Spanoudes🇨🇾 · M. Costa🇨🇾 · I. Karpasitis🇨🇾 · T. Pafitis🇨🇾 · G. Panagopoulos🇺🇸 · H. Panagopoulos🇨🇾 · A. Skouroupathis🇨🇾

   We study a gauge-invariant renormalization scheme (GIRS) for composite operators, regularized on the lattice, by extending the coordinate space (X-space) scheme proposed some years ago. In this scheme, Green's functions of products of gauge-invariant operators located at different spacetime points are considered. Due to the gauge-invariant nature of GIRS, gauge fixing is not needed in the lattice simulations. Also, when operator mixing occurs, the gauge-variant operators (BRST variations and operators which vanish by the equations of motion) can be safely excluded from the renormalization process. We propose a number of variants of GIRS, including integration over time slices of the operator insertion point in a Green's function, which may lead to reduced statistical noise in lattice simulations. We employ these variants in the renormalization of fermion bilinear operators and the study of mixing between the gluon and quark energy-momentum tensor operators. We extract the one-loop conversion factors relating the nonperturbative renormalization factors in different versions of GIRS to the reference scheme of $\overline{\mathrm{MS}}$.

   hep-latPoS(2022)·0 citations
2. 02*

   Investigating quark confinement from the viewpoint of lattice gauge-scalar models

   Ryu Ikeda🇯🇵 · Kei-Ichi Kondo🇯🇵

   In this talk, first, we show that the color $N$-dependent area law falloffs of the double-winding Wilson loop averages for the $SU(N)$ lattice gauge model are reproduced from the $Z_N$ lattice Abelian gauge model due to the center group dominance in quark confinement. Next, we discuss lattice gauge-scalar models which allow analytic continuation for gauge invariant operators between confinement region and Higgs region. Applying the cluster expansion, we try to understand non-trivial contribution from scalar field in quark confinement mechanism. In order to understand quark confinement further, moreover, we study double-winding Wilson loop averages in the analytical region on the phase diagram.

   hep-lathep-thPoS(2022)·0 citations
3. 03*

   Quantum Field Theories with Tensor Renormalization Group

   Shinichiro Akiyama🇯🇵 · Yoshinobu Kuramashi🇯🇵 · Yusuke Yoshimura🇯🇵

   We report recent progress on the application of the tensor renormalization group (TRG) to quantum field theories pursued by the Tsukuba group. We explain how to treat the scalar, fermion, and gauge theories with the TRG method presenting the results for the phase transitions in the (3+1)-dimensional ((3+1)$d$) complex ${\varphi }^4$ theory at finite density, (1+1)$d$ pure U(1) lattice gauge theory with a $\theta$ term, (3+1)$d$ Nambu--Jona-Lasinio model at finite density and (1+1)$d$ and (2+1)$d$ Hubbard models at an arbitrary chemical potential. It is demonstrated that the TRG method is free from the sign problem in practical calculations and applicable to the four-dimensional models.

   hep-latcond-mat.stat-mechPoS(2022)·5 citations
4. 04*

   Looking at the analytic structure of Landau gauge propagators

   Orlando Oliveira🇵🇹 · Alexandre F. Falcão🇵🇹 · Paulo J. Silva🇵🇹

   We report on a study of the analytical structure of the Landau gauge gluon, ghost and quark propagators taken from lattice simulations using large physical volumes, to better access the IR region, and large gauge ensembles to reduce the statistical uncertainties. The investigation uses Padé approximants to look at poles and branch cuts for each of the propagators. For the gluon propagator we identify complex conjugate poles and a branch point. For the ghost propagator the procedure identifies a pole at zero momentum and a branch point for Minkowski-like momenta. The quark propagator appears to have a pole for Minkowski-like momenta that is correlated with the pion mass as expected from PCAC.

   hep-lathep-thPoS(2022)·4 citations
5. 05*

   Lattice gauge symmetry in neural networks

   Matteo Favoni🇦🇹 · Andreas Ipp🇦🇹 · David I. Müller🇦🇹 · Daniel Schuh🇦🇹

   We review a novel neural network architecture called lattice gauge equivariant convolutional neural networks (L-CNNs), which can be applied to generic machine learning problems in lattice gauge theory while exactly preserving gauge symmetry. We discuss the concept of gauge equivariance which we use to explicitly construct a gauge equivariant convolutional layer and a bilinear layer. The performance of L-CNNs and non-equivariant CNNs is compared using seemingly simple non-linear regression tasks, where L-CNNs demonstrate generalizability and achieve a high degree of accuracy in their predictions compared to their non-equivariant counterparts.

   hep-latcs.LGhep-phhep-th+1PoS(2022)·5 citations
6. 06*

   General purpose lattice QCD code set Bridge++ 2.0 for high performance computing

   Yutaro Akahoshi🇯🇵 · Sinya Aoki🇯🇵 · Tatsumi Aoyama🇯🇵 · Issaku Kanamori🇯🇵 · Kazuyuki Kanaya🇯🇵 · Hideo Matsufuru🇯🇵 · Yusuke Namekawa🇯🇵 · Hidekatsu Nemura🇯🇵 · Yusuke Taniguchi🇯🇵

   Bridge++ is a general-purpose code set for a numerical simulation of lattice QCD aiming at a readable, extensible, and portable code while keeping practically high performance. The previous version of Bridge++ is implemented in double precision with a fixed data layout. To exploit the high arithmetic capability of new processor architecture, we extend the Bridge++ code so that optimized code is available as a new branch, i.e., an alternative to the original code. This paper explains our strategy of implementation and displays application examples to the following architectures and systems: Intel AVX-512 on Xeon Phi Knights Landing, Arm A64FX-SVE on Fujitsu A64FX (Fugaku), NEC SX-Aurora TSUBASA, and GPU cluster with NVIDIA V100.

   hep-latJ.Phys.Conf.Ser.(2022)·16 citations
7. 07*

   Overview of lattice calculations of the $x$-dependence of PDFs, GPDs and TMDs

   Krzysztof Cichy🇵🇱

   For a long time, lattice QCD was unable to address the $x$-dependence of partonic distributions, direct access to which is impossible in Euclidean spacetime. Recent years have brought a breakthrough for such calculations when it was realized that partonic light-cone correlations can be accessed through spatial correlations computable on the lattice. Appropriately devised observables can be factorized into physical PDFs via a perturbative procedure called matching, analogous to the standard factorization of experimental cross sections. In this short review, aimed at a broader high-energy and nuclear physics community, we discuss the recent highlights of this research program. Key concepts are outlined, followed by a case study illustrating the typical stage of current lattice extractions and by a brief review of the most recent explorations. We finalize with a number of messages for the prospects of lattice determinations of partonic structure.

   hep-lathep-exhep-phnucl-thEPJ Web Conf.(2022)·40 citations
8. 08*

   Complex spacing ratios of the non-Hermitian Dirac operator in universality classes AI${}^{†}$ and AII${}^{†}$

   Takuya Kanazawa🇯🇵 · Tilo Wettig🇩🇪

   We consider non-Hermitian Dirac operators in QCD-like theories coupled to a chiral U(1) potential or an imaginary chiral chemical potential. We show that in the continuum they fall into the recently discovered universality classes AI${}^{†}$ or AII${}^{†}$ of random matrix theory if the fermions transform in pseudoreal or real representations of the gauge group, respectively. For staggered fermions on the lattice this correspondence is reversed. We verify our predictions by computing spacing ratios of complex eigenvalues, whose distribution is universal without the need for unfolding.

   hep-latPoS(2022)·1 citation
9. 09*

   $\pi -\pi$ scattering, QED and finite-volume quantization

   Norman Christ🇺🇸 · Xu Feng🇨🇳 · Joseph Karpie🇺🇸 · Tuan Nguyen🇺🇸

   Using the Coulomb gauge formulation of QED we present a lattice QCD procedure to calculate the ${\pi }^{+}{\pi }^{+}$ scattering phase shift including the effects of the Coulomb potential which appears in this formulation. The approach described here incorporates the effects of relativity and avoids finite-volume corrections that vanish as a power of the volume in which the lattice calculation is performed. This is the first step in developing a complete lattice QCD calculation of the electromagnetic and isospin-breaking light-quark mass contributions to ${\epsilon }^{\prime }$, the parameter describing direct CP violating effects in $K_L\to \pi \pi$ decay.

   hep-latPRD(2022)·17 citations
10. 10*

    Logarithmic corrections to ${\mathbf{a}}^2$ scaling in lattice QCD with Wilson and Ginsparg-Wilson quarks

    Nikolai Husung🇬🇧 · Peter Marquard🇩🇪 · Rainer Sommer🇩🇪

    We analyse the leading logarithmic corrections to the $a^2$ scaling of lattice artefacts in QCD, following the seminal work of Balog, Niedermayer and Weisz in the O(n) non-linear sigma model. Limiting the discussion to contributions from the action, the leading logarithmic corrections can be determined by the anomalous dimensions of mass-dimension 6 operators. These operators form a minimal on-shell basis of the Symanzik Effective Theory. We present results for non-perturbatively O($a$) improved Wilson and Ginsparg-Wilson quarks.

    hep-latPoS(2022)·2 citations
11. 11*

    Precision $B^{\ast }B\pi$ coupling from three-flavor lattice QCD

    Antoine Gérardin🇫🇷 · Jochen Heitger🇩🇪 · Simon Kuberski🇩🇪 · Hubert Simma🇩🇪 · Rainer Sommer🇩🇪

    We consider three-flavor QCD and perform a determination of the low-energy coupling ${\hat{g}}_{\chi }$ of SU(2) Heavy Meson Chiral Perturbation Theory. It is the $B^{\ast }B\pi$ coupling in the limit of static heavy and chiral light quarks and has not been determined with precision thus far. The calculation is performed on a large set of the $2+1$ flavor CLS ensembles with pion masses from 420 MeV down to 130 MeV. This allows us to significantly reduce the systematic uncertainty from the chiral extrapolation compared to previous works. Only a weak dependence on the lattice spacing is visible in our results.

    hep-latPoS(2022)·4 citations
12. 12*

    Dissipation-induced dynamical phase transition in postselected quantum trajectories

    Tomoya Hayata🇯🇵 · Yoshimasa Hidaka🇯🇵 · Arata Yamamoto🇯🇵

    It is known that effects of dissipation or measurement backreaction in postselected quantum trajectories are described by non-Hermitian Hamiltonian, but their consequences in real-time dynamics of many-body systems are yet to be elucidated. Through a study of a non-Hermitian Hubbard model, we reveal a novel dissipation-induced dynamical phase transition in postselected quantum trajectories, where time controls the strength of postselection and becomes the intrinsic parameter inducing the phase transition. Our findings are testable in ultracold atom experiments and may open a new avenue in the dissipative engineering of quantum systems.

    ↳ cond-mat.quant-gascond-mat.stat-mechcond-mat.str-elhep-lat+1PTEP(2023)·4 citations
13. 13*

    Large-$N$ Chern insulators: lattice field theory and quantum simulation approaches to correlation effects in the quantum anomalous Hall effect

    L. Ziegler🇪🇸 · E. Tirrito🇮🇹 · M. Lewenstein🇪🇸 · S. Hands🇬🇧 · A. Bermudez🇪🇸

    Four-Fermi quantum field theories in (2+1) dimensions lie among the simplest models in high-energy physics, the understanding of which requires a non-perturbative lattice formulation addressing their strongly-coupled fixed points. These lattice models are also relevant in condensed matter, as they offer a neat playground to explore strong correlations in the quantum anomalous Hall (QAH) effect. We give a detailed description of our multidisciplinary approach to understand the fate of the QAH phases as the four-Fermi interactions are increased, which combines strong-coupling and effective-potential techniques, unveiling a rich phase diagram with large-$N$ Chern insulators and Lorentz-breaking fermion condensates. Moreover, this toolbox can be enlarged with recent advances in quantum information science, as we show that tensor-network algorithms based on projected entangled pairs can be used to improve our understanding of the strong-coupling limit. We also present a detailed scheme that uses ultra-cold atoms in optical lattices with synthetic spin-orbit coupling to build quantum simulators of these four-Fermi models. This yields a promising alternative to characterise the strongly-coupled fixed points and, moreover, could also explore real-time dynamics and finite-fermion densities.

    ↳ cond-mat.quant-gascond-mat.str-elhep-latquant-phAnnals Phys.(2022)·19 citations
14. 14*

    New hadron configuration: The double-gluon hybrid state

    Hua-Xing Chen🇨🇳 · Wei Chen🇨🇳 · Shi-Lin Zhu🇨🇳

    This is the first study on the double-gluon hybrid, which consists of one valence quark and one valence antiquark together with two valence gluons. We concentrate on the one with the exotic quantum number $J^{PC}=2^{+-}$ that conventional $\bar{q}q$ mesons can not reach. We apply QCD sum rule method to evaluate its mass to be $2.26_{-0.25}^{+0.20}$ GeV, and study its possible decay patterns. Especially, its three-meson decay patterns are generally not suppressed severely compared to two-meson decay patterns, so the $S$-wave three-meson decay channels $f_1\omega \pi /f_1\rho \pi$ can be useful in identifying its nature, which is of particular importance to the direct test of QCD in the low energy sector.

    ↳ hep-phhep-exhep-latnucl-ex+1PRD(2022)·16 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.