Thu·Oct 14, 2021Thursday·October 14, 2021

1. 01*

   Recent Progress in Lattice Parton-Distribution Calculations

   Huey-Wen Lin🇺🇸

   The large-momentum effective theory (LaMET) framework has been widely used to determine the Bjorken-$x$ dependence of parton distribution functions (PDFs) in lattice-QCD hadron-structure calculations. In this proceeding, I highlighted selected recent lattice-QCD results on parton distributions from MSULat group. We use clover valence fermions on ensembles generated by MILC Collaboration with lattice spacing $a\approx 0.06$, 0.09, and 0.12 fm, with $M_{\pi }L\approx 4$, and with pion masses including 135, 220 and 310 MeV and $N_f=2+1+1$ flavors of highly improved staggered dynamical quarks. Results include the continuum-physical isovector nucleon PDF, a first study of the strange and charm PDFs and the pion and kaon valence-quark PDFs. We also reported results on the $Q^2$ and $x$ dependence of nucleon isovector unpolarized and helicity GPDs calculated directly at physical pion mass; we also make a comparison of the GPDs with the traditional moment methods from other lattice calculations.

   hep-lathep-phPoS(2022)·3 citations
2. 02*

   Analytic expansions of multi-hadron finite-volume energies: I. Two-particle states

   Dorota M. Grabowska🇨🇭 · Maxwell T. Hansen🇬🇧

   We derive analytic expansions for the finite-volume energies of weakly-interacting two-particle systems, using the general relations between scattering amplitudes and energies derived by Lüscher and others. The relations hold for ground and excited states with both zero and non-zero total momentum in the finite-volume frame. A number of instructive aspects arise in the derivation, including the role of accidental degeneracies and the importance of defining a power-counting scheme in the expansions. The results give intuition concerning the imprint of weakly-interacting systems on the energy spectrum, while also providing a useful basis for the analogous results concerning three-particle excited states, to appear.

   hep-latJHEP(2022)·13 citations
3. 03*

   Kaon decays and other hadronic processes in lattice QCD

   Fernando Romero-López🇪🇸

   This thesis deals with the study of properties and interactions of light mesons. Specifically, we focus on hadronic decay and scattering processes, which are dominated by effects of the strong interaction in the low-energy regime. A peculiarity of the strong interaction is that perturbative expansions fail at hadronic energy scales. Thus, genuine nonperturbative tools are essential to obtain first-principles predictions. Here we use Lattice Field Theory, and Effective Field Theories. The mathematical formulation of Quantum Chromodynamics (QCD) and the methods to resolve its dynamics will be addressed in Chapter 1. The research of this dissertation is divided in two parts. Chapter 2 describes our study of the 't Hooft limit of QCD using lattice simulations, while in Chapter 3 we consider processes that involve multiparticle states. The 't Hooft limit provides a simplification of nonabelian gauge theories that leads to nonperturbative predictions. We will analyze the scaling with the number of colours of various observables, such as meson masses, decay constants and weak matrix elements. A question we address is the origin of the long-standing puzzle of the $\Delta I=1/2$ rule, that is, the large hierarchy in the isospin amplitudes of the $K\to \pi \pi$ weak decay. Regarding multiparticle processes, we will discuss generalizations of the Lüscher formalism to explore three-particle processes from lattice simulations. The focus will be on our contributions, such as our implementation of the finite-volume formalism that includes higher partial waves, and the first application of the formalism to a full lattice QCD spectrum. We will also comment on the extension of the approach to generic three-pion systems. A summary in Spanish will be given in Chapter 4. The final part of the thesis (Part II) includes the peer-reviewed publications in their original published form.

   hep-lathep-ph0 citations
4. 04*

   Quantized Noncommutative Geometry from Multitrace Matrix Models

   Badis Ydri🇩🇿 · Ramda Khaled🇩🇿 · Cherine Soudani🇩🇿

   In this article the geometry of quantum gravity is quantized in the sense of being noncommutative (first quantization) but it is also quantized in the sense of being emergent (second quantization). A new mechanism for quantum geometry is proposed in which noncommutative geometry can emerge from "one-matrix multitrace scalar matrix models" by probing the statistical physics of commutative phases of matter. This is in contrast to the usual mechanism in which noncommutative geometry emerges from "many-matrix singletrace Yang-Mills matrix models" by probing the statistical physics of noncommutative phases of gauge theory. In this novel scenario quantized geometry emerges in the form of a transition between the two phase diagrams of the real quartic matrix model and the noncommutative scalar phi-four field theory. More precisely, emergence of the geometry is identified here with the emergence of the uniform-ordered phase and the corresponding commutative (Ising) and noncommutative (stripe) coexistence lines. The critical exponents and the Wigner's semicircle law are used to determine the dimension and the metric respectively. Arguments from the saddle point equation, from Monte Carlo simulation and from the matrix renormalization group equation are provided in support of this scenario.

   ↳ hep-thgr-qchep-latInt.J.Mod.Phys.A(2022)·10 citations
5. 05*

   Applications of the Perturbative Gradient Flow

   Fabian Lange🇩🇪

   Over the last decade the gradient flow formalism became an important tool for lattice simulations of Quantum Chromodynamics. It offers remarkable renormalization properties which pave the way for cross-fertilization between perturbative and lattice calculations. In this contribution we discuss the perturbative approach. As first application we compute vacuum expectation values of flowed operators which could help to extract parameters like the strong coupling constant from lattice simulations. Afterwards, we apply the flowed operator product expansion to the time-ordered product of two currents which could be employed for an alternative first-principle evaluation of vacuum polarization functions on the lattice.

   ↳ hep-phhep-latSciPost Phys.Proc.(2022)·1 citation
6. 06*

   Suppressing nonperturbative gauge errors in the thermodynamic limit using local pseudogenerators

   Maarten Van Damme🇧🇪 · Julius Mildenberger🇮🇹 · Fabian Grusdt🇩🇪 · Philipp Hauke🇮🇹 · Jad C. Halimeh🇮🇹

   With recent progress in quantum simulations of lattice-gauge theories, it is becoming a pressing question how to reliably protect the gauge symmetry that defines such models. In a recent work [J. C. Halimeh \textit{et al.}, arXiv:2108.02203], an experimentally feasible gauge-protection scheme has been proposed that is based on the concept of a \textit{local pseudogenerator}, which is required to act identically to the full gauge-symmetry generator in the target gauge sector, but not necessarily outside of it. The scheme has been analytically and numerically shown to reliably stabilize lattice gauge theories in the presence of perturbative errors on finite-size analog quantum-simulation devices. In this work, through uniform matrix product state calculations, we demonstrate the efficacy of this scheme for nonperturbative errors in analog quantum simulators up to all accessible evolution times in the thermodynamic limit, where it is \textit{a priori} neither established nor expected that this scheme will succeed. Our results indicate the presence of an emergent gauge symmetry in an adjusted gauge theory even in the thermodynamic limit, which is beyond our analytic predictions. Additionally, we show through quantum circuit model calculations that gauge protection with local pseudogenerators also successfully suppresses gauge violations on finite quantum computers that discretize time through Trotterization. Our results firm up the robustness and feasibility of the local pseudogenerator as a viable tool for enforcing gauge invariance in modern quantum simulators and NISQ devices.

   ↳ quant-phcond-mat.quant-gascond-mat.str-elhep-lat+1Commun.Phys.(2025)·22 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.