Mon·Dec 19, 2022Monday·December 19, 2022

1. 01*

   The International Lattice Data Grid -- towards FAIR Data

   Frithjof Karsch🇩🇪 · Hubert Simma🇩🇪 · Tomoteru Yoshie🇯🇵

   The International Lattice Data Grid (ILDG) is a community-wide initiative to realize the sharing of primary data from lattice QCD simulations according to the principles of FAIR data. We recall the basic concepts of ILDG as a federation of autonomous regional grids with common standards for (meta-)data and services, and report on current activities, progress, and plans to restore and extend the usability of ILDG.

   hep-latPoS(2023)·11 citations
2. 02*

   Probing the energy-smeared R-ratio on the lattice

   Constantia Alexandrou🇨🇾 · Simone Bacchio🇨🇾 · Alessandro De Santis🇮🇹 · Petros Dimopoulos🇫🇷 · Jacob Finkenrath🇨🇾 · Roberto Frezzotti🇮🇹 · Giuseppe Gagliardi🇮🇹 · Marco Garofalo🇩🇪 · Kyriakos Hadjiyiannakou🇨🇾 · Bartosz Kostrzewa🇩🇪 · Karl Jansen🇩🇪 · Vittorio Lubicz🇮🇹 and 6 other authors

   We present a first-principles lattice QCD investigation of the $R$-ratio between the $e^{+}{e}^{-}$ cross-section into hadrons and that into muons. By using the method of Ref.[1], that allows to extract smeared spectral densities from Euclidean correlators, we compute the $R$-ratio convoluted with Gaussian smearing kernels of widths of about $600$ MeV and central energies from $220$ MeV up to $2.5$ GeV. Our theoretical results are compared with the corresponding quantities obtained by smearing the KNT19 compilation [2] of $R$-ratio experimental measurements with the same kernels and, by centring the Gaussians in the region around the $\rho$-resonance peak, a tension of about three standard deviations is observed. From the phenomenological perspective, we have not included yet in our calculation QED and strong isospin-breaking corrections and this might affect the observed tension. From the methodological perspective, our calculation demonstrates that it is possible to study the $R$-ratio in Gaussian energy bins on the lattice at the level of accuracy required in order to perform precision tests of the Standard Model.

   hep-lathep-phPRL(2023)·93 citations
3. 03*

   Learning Trivializing Gradient Flows for Lattice Gauge Theories

   Simone Bacchio🇨🇾 · Pan Kessel🇩🇪 · Stefan Schaefer🇩🇪 · Lorenz Vaitl🇩🇪

   We propose a unifying approach that starts from the perturbative construction of trivializing maps by Lüscher and then improves on it by learning. The resulting continuous normalizing flow model can be implemented using common tools of lattice field theory and requires several orders of magnitude fewer parameters than any existing machine learning approach. Specifically, our model can achieve competitive performance with as few as 14 parameters while existing deep-learning models have around 1 million parameters for $SU(3)$ Yang--Mills theory on a $16^2$ lattice. This has obvious consequences for training speed and interpretability. It also provides a plausible path for scaling machine-learning approaches toward realistic theories.

   hep-latPRD(2023)·54 citations
4. 04*

   Constructing static quark-anti-quark creation operators from Laplacian eigenmodes

   Roman Höllwieser🇩🇪 · Francesco Knechtli🇩🇪 · Tomasz Korzec🇩🇪 · Michael Peardon🇮🇪 · Juan Andrés Urrea-Niño🇩🇪

   We investigate static quark anti-quark operators based on trial states formed from eigenvectors of the covariant three-dimensional lattice Laplace operator. We test the method by computing the static quark-anti-quark potential and comparing results to standard Wilson loop measurements. The new method is efficient not only for on-axis, but also for many off-axis quark-anti-quark separations when a fine spatial resolution is required. We further improve the ground-state overlap by using multiple eigenvector pairs, weighted with Gaussian profile functions of the eigenvalues, providing a variational basis. The method presented here can be applied to potential functions for all possible excitations of a gluonic string with fixed ends, hybrid or tetra-quark potentials, as well as static-light systems and allows visualization of the spatial distribution of the Laplace trial states.

   hep-latPRD(2023)·10 citations
5. 05*

   Stabilizing complex Langevin for real-time gauge theories with an anisotropic kernel

   Kirill Boguslavski🇦🇹 · Paul Hotzy🇦🇹 · David I. Müller🇦🇹

   The complex Langevin (CL) method is a promising approach to overcome the sign problem that occurs in real-time formulations of quantum field theories. Using the Schwinger-Keldysh formalism, we study SU($N_c$) gauge theories with CL. We observe that current stabilization techniques are insufficient to obtain correct results. Therefore, we revise the discretization of the CL equations on complex time contours, find a time reflection symmetric formulation and introduce a novel anisotropic kernel that enables CL simulations on discretized complex time paths. Applying it to SU(2) Yang-Mills theory in 3+1 dimensions, we obtain unprecedentedly stable results that we validate using additional observables and that can be systematically improved. For the first time, we are able to simulate non-Abelian gauge theory on time contours whose real-time extent exceeds its inverse temperature. Thus, our approach may pave the way towards an ab-initio real-time framework of QCD in and out of equilibrium with a potentially large impact on the phenomenology of heavy-ion collisions.

   hep-lathep-phJHEP(2023)·28 citations
6. 06*

   QCD Factorization of Quasi Generalized Gluon Distributions

   J.P. Ma🇨🇳 · Z.Y. Pang🇨🇳 · C.P. Zhang🇺🇸 · G.P. Zhang🇨🇳

   We study the factorization relations between quasi gluon GPDs and twist-2 GPDs. The perturbative coefficient functions are obtained at one-loop level. They are free from any collinear- or I.R. divergences. Unlike the case of the factorization of quasi quark GPDs at one-loop, we have to add ghost contributions for the factorization of quasi gluon GPDs in order to obtain gauge-invariant results. In general, operators will be mixed beyond tree-level. Our work shows that the mixing pattern of the nonlocal operators in quasi gluon GPDs is the same as local operators, i.e., the nonlocal operators considered are mixed with gauge-invariant operators, BRST-variation operators and operators involving EOM operator. The factorization relations are obtained for all quasi gluon GPDs. Taking the forward limit, we also obtain the relations between quasi gluon PDFs and twist-2 PDFs.

   ↳ hep-phhep-latJHEP(2023)·14 citations
7. 07*

   Estimating truncation effects of quantum bosonic systems using sampling algorithms

   Masanori Hanada🇬🇧 · Junyu Liu🇺🇸 · Enrico Rinaldi🇺🇸 · Masaki Tezuka🇯🇵

   To simulate bosons on a qubit- or qudit-based quantum computer, one has to regularize the theory by truncating infinite-dimensional local Hilbert spaces to finite dimensions. In the search for practical quantum applications, it is important to know how big the truncation errors can be. In general, it is not easy to estimate errors unless we have a good quantum computer. In this paper, we show that traditional sampling methods on classical devices, specifically Markov Chain Monte Carlo, can address this issue for a rather generic class of bosonic systems with a reasonable amount of computational resources available today. As a demonstration, we apply this idea to the scalar field theory on a two-dimensional lattice, with a size that goes beyond what is achievable using exact diagonalization methods. This method can be used to estimate the resources needed for realistic quantum simulations of bosonic theories, and also, to check the validity of the results of the corresponding quantum simulations.

   ↳ quant-phcs.AIcs.LGhep-lat+1Mach.Learn.Sci.Tech.(2023)·16 citations
8. 08*

   Microcanonical Hamiltonian Monte Carlo

   Jakob Robnik🇺🇸 · G. Bruno De Luca🇺🇸 · Eva Silverstein🇺🇸 · Uroš Seljak🇺🇸

   We develop Microcanonical Hamiltonian Monte Carlo (MCHMC), a class of models which follow a fixed energy Hamiltonian dynamics, in contrast to Hamiltonian Monte Carlo (HMC), which follows canonical distribution with different energy levels. MCHMC tunes the Hamiltonian function such that the marginal of the uniform distribution on the constant-energy-surface over the momentum variables gives the desired target distribution. We show that MCHMC requires occasional energy conserving billiard-like momentum bounces for ergodicity, analogous to momentum resampling in HMC. We generalize the concept of bounces to a continuous version with partial direction preserving bounces at every step, which gives an energy conserving underdamped Langevin-like dynamics with non-Gaussian noise (MCLMC). MCHMC and MCLMC exhibit favorable scalings with condition number and dimensionality. We develop an efficient hyperparameter tuning scheme that achieves high performance and consistently outperforms NUTS HMC on several standard benchmark problems, in some cases by more than an order of magnitude.

   ↳ stat.COastro-ph.IMhep-lathep-th24 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.