Mon·Dec 6, 2021Monday·December 6, 2021

1. 01*

   LeapfrogLayers: A Trainable Framework for Effective Topological Sampling

   Sam Foreman🇺🇸 · Xiao-Yong Jin🇺🇸 · James C. Osborn🇺🇸

   We introduce LeapfrogLayers, an invertible neural network architecture that can be trained to efficiently sample the topology of a 2D $U(1)$ lattice gauge theory. We show an improvement in the integrated autocorrelation time of the topological charge when compared with traditional HMC, and look at how different quantities transform under our model. Our implementation is open source, and is publicly available on github at https://github.com/saforem2/l2hmc-qcd.

   hep-latcs.LGPoS(2022)·13 citations
2. 02*

   Bottomonium spectral widths at nonzero temperature using maximum likelihood

   Thomas Spriggs🇬🇧 · Gert Aarts🇬🇧 · Chris Allton🇬🇧 · Timothy Burns🇬🇧 · Benjamin Jäger🇩🇰 · Seyong Kim🇰🇷 · Maria Paola Lombardo🇮🇹 · Sam Offler🇬🇧 · Ben Page🇬🇧 · Sinéad M. Ryan🇮🇪 · Jon-Ivar Skullerud🇮🇪

   We present progress results from the Fastsum collaboration's programme to determine the spectrum of the bottomonium system as a function of temperature using a variety of approaches. In these proceedings, the Maximum Likelihood approach is used with an Ansatz comprising of a Gaussian spectral function for the ground state. Fastsum anisotropic lattices with 2+1 dynamical quark flavours were used with temperatures ranging from 47 to 375 MeV.

   hep-latPoS(2022)·8 citations
3. 03*

   Most charming dibaryon near unitarity

   Yan Lyu🇨🇳 · Hui Tong🇨🇳 · Takuya Sugiura🇯🇵 · Sinya Aoki🇯🇵 · Takumi Doi🇯🇵 · Tetsuo Hatsuda🇯🇵 · Jie Meng🇨🇳 · Takaya Miyamoto🇯🇵

   We present a first study on a pair of triply charmed baryons, ${\Omega }_{ccc}{\Omega }_{ccc}$ in the ${}^1{S}_0$ channel, on the basis of the HAL QCD method. The measurements are perfomed on the $(2+1)$-flavor lattice QCD configurations with nearly physical light-quark masses and physical charm-quark mass. We show that the system with the Coulomb repulsion taking into account the charge form factor of ${\Omega }_{ccc}$ leads to the scattering length $a_0^{\mathrm{C}}\simeq -19$ fm and the effective range $r_{\mathrm{eff}}^{\mathrm{C}}\simeq 0.45$ fm, which indicates ${\Omega }_{ccc}{\Omega }_{ccc}$ is located in the unitary regime.

   hep-lathep-phnucl-thPoS(2022)·5 citations
4. 04*

   A new technique for solving the freezing problem in the complex Langevin simulation of 4D SU(2) gauge theory with a theta term

   Akira Matsumoto🇯🇵 · Kohta Hatakeyama🇯🇵 · Mitsuaki Hirasawa🇯🇵 · Masazumi Honda🇯🇵 · Yuta Ito🇯🇵 · Jun Nishimura🇯🇵 · Atis Yosprakob🇯🇵

   We apply the complex Langevin method (CLM) to overcome the sign problem in 4D SU(2) gauge theory with a theta term extending our previous work on the 2D U(1) case. The topology freezing problem can be solved by using open boundary conditions in all spatial directions, and the criterion for justifying the CLM is satisfied even for large $\theta$ as far as the lattice spacing is sufficiently small. However, we find that the CP symmetry at $\theta =\pi$ remains to be broken explicitly even in the continuum and infinite-volume limits due to the chosen boundary conditions. In particular, this prevents us from investigating the interesting phase structures suggested by the 't Hooft anomaly matching condition. We also try the so-called subvolume method, which turns out to have a similar problem. We therefore discuss a new technique within the CLM, which enables us to circumvent the topology freezing problem without changing the boundary conditions.

   hep-lathep-thPoS(2022)·6 citations
5. 05*

   Grid on QPACE 4

   Peter Georg🇩🇪 · Nils Meyer🇩🇪 · Stefan Solbrig🇩🇪 · Tilo Wettig🇩🇪

   In 2020 we deployed QPACE 4, which features 64 Fujitsu A64FX model FX700 processors interconnected by InfiniBand EDR. QPACE 4 runs an open-source software stack. For Lattice QCD simulations we ported the Grid LQCD framework to support the ARM Scalable Vector Extension (SVE). In this contribution we discuss our SVE port of Grid, the status of SVE compilers and the performance of Grid. We also present the benefits of an alternative data layout of complex numbers for the Domain Wall operator.

   hep-latcs.DCPoS(2022)·8 citations
6. 06*

   Tensor-network simulation of the strong-coupling $U(N)$ model

   Pascal Milde🇩🇪 · Jacques Bloch🇩🇪 · Robert Lohmayer🇩🇪

   We apply tensor network methods to study the strong-coupling $U(N)$ model in its dimer formulation. In three and four dimensions, we investigate the chiral condensate as a function of the quark mass and the degree of the symmetry group, and find good agreement with Monte Carlo simulations. Particularly interesting is the study of chiral symmetry breaking as a function of the mass and the volume, which clearly shows that this symmetry is spontaneously broken in the limit of infinite volume and zero mass.

   hep-latcond-mat.stat-mechPoS(2022)·9 citations
7. 07*

   SU(3) hybrid static potentials at small quark-antiquark separations from fine lattices

   Carolin Schlosser🇩🇪 · Marc Wagner🇩🇪

   We summarize our recent lattice gauge theory computation of the ${\Pi }_u$ and ${\Sigma }_u^{-}$ hybrid static potentials at small quark-antiquark separations. We provide parameterizations of the resulting lattice data points, which can be used for investigating masses and properties of heavy hybrid mesons in the Born-Oppenheimer approximation.

   hep-latSciPost Phys.Proc.(2022)·3 citations
8. 08*

   Optimizing Distillation for charmonium and glueballs

   Francesco Knechtli🇩🇪 · Tomasz Korzec🇩🇪 · Mike Peardon🇮🇪 · Juan Andrés Urrea Niño🇩🇪

   We study the charmonium spectrum on an ensemble with two heavy dynamical quarks with a mass at half the physical charm quark mass. Operators for different quantum numbers are used in the framework of distillation with different smearing profiles to increase the overlap with ground and excited states. The use of exact distillation, large statistics and the absence of light quarks gives robust results for the charmonium spectrum. We also present preliminary results for the glueball spectrum in this theory.

   hep-latPoS(2022)·4 citations
9. 09*

   Accessing scattering amplitudes using quantum computers

   Raul A. Briceño🇺🇸 · Marco A. Carrillo🇺🇸 · Juan V. Guerrero🇺🇸 · Maxwell T. Hansen🇬🇧 · Alexandru M. Sturzu🇺🇸

   Future quantum computers may serve as a tool to access non-perturbative real-time correlation functions. In this talk, we discuss the prospects of using these to study Compton scattering for arbitrary kinematics. The restriction to a finite-volume spacetime, unavoidable in foreseeable quantum-computer simulations, must be taken into account in the formalism for extracting scattering observables. One approach is to work with a non-zero $iϵ$-prescription in the Fourier transform to definite momentum and then to estimate an ordered double limit, in which the spacetime volume is sent to infinity before $ϵ$ is sent to $0$. For the amplitudes and parameters considered here, we find that significant volume effects arise, making the required limit very challenging. We present a practical solution to this challenge that may allow for future determinations of deeply virtual Compton scattering amplitudes, as well as many other reactions that are presently outside the scope of standard lattice QCD calculations.

   hep-latPoS(2022)·7 citations
10. 10*

    A fully non-perturbative charm-quark tuning using machine learning

    R. J. Hudspith🇩🇪 · D. Mohler🇩🇪

    We present a relativistic heavy-quark action tuning for the charm sector on ensembles generated by the CLS consortium. We tune a particular 5-parameter action in an entirely non-perturbative and -- up to the chosen experimental input -- model-independent way using machine learning and the continuum experimental charmonium ground-state masses with various quantum numbers. In the end we are reasonably successful; obtaining a set of simulation parameters that we then verify produces the expected spectrum. In the future, we will use this action for finite-volume calculations of hadron-hadron scattering.

    hep-latPRD(2022)·12 citations
11. 11*

    Spectral reconstruction in NRQCD via the Backus-Gilbert method

    Benjamin Page🇬🇧 · Gert Aarts🇬🇧 · Chris Allton🇬🇧 · Benjamin Jäger🇩🇰 · Seyong Kim🇰🇷 · Maria Paola Lombardo🇮🇹 · Sam Offler🇬🇧 · Sinead M. Ryan🇮🇪 · Jon-Ivar Skullerud🇮🇪 · Thomas Spriggs🇬🇧

    We present progress results from the FASTSUM collaboration's programme to determine the spectrum of the bottomonium system as a function of temperature using a variety of approaches. In this contribution, the Backus Gilbert method is used to reconstruct spectral functions from NRQCD meson correlator data from FASTSUM's anisotropic ensembles at nonzero temperature. We focus in particular on the resolving power of the method, providing a demonstration of how the underlying resolution functions can be probed by exploiting the Laplacian nature of the NRQCD kernel. We conclude with estimates of the bottomonium ground state mass and widths at nonzero temperature.

    hep-latPoS(2022)·10 citations
12. 12*

    Qubit Regularization and Qubit Embedding Algebras

    Hanqing Liu🇺🇸 · Shailesh Chandrasekharan🇺🇸

    Qubit regularization is a procedure to regularize the infinite dimensional local Hilbert space of bosonic fields to a finite dimensional one, which is a crucial step when trying to simulate lattice quantum field theories on a quantum computer. When the qubit-regularized lattice quantum fields preserve important symmetries of the original theory, qubit regularization naturally enforces certain algebraic structures on these quantum fields. We introduce the concept of qubit embedding algebras (QEAs) to characterize this algebraic structure associated with a qubit regularization scheme. We show a systematic procedure to derive QEAs for the O(N) lattice spin models and the SU(N) lattice gauge theories. While some of the QEAs we find were discovered earlier in the context of the D-theory approach, our method shows that QEAs are far more richer. A more complete understanding of the QEAs could be helpful in recovering the fixed points of the desired quantum field theories.

    hep-lathep-thquant-phSymmetry(2022)·30 citations
13. 13*

    Reconstruction of bottomonium spectral functions in thermal QCD using Kernel Ridge Regression

    Sam Offler🇬🇧 · Gert Aarts🇬🇧 · Chris Allton🇬🇧 · Benjamin Jäger🇩🇰 · Seyong Kim🇰🇷 · Maria-Paola Lombardo🇮🇹 · Benjamin Page🇬🇧 · Sinead M. Ryan🇮🇪 · Jon-Ivar Skullerud🇮🇪 · Thomas Spriggs🇬🇧

    We discuss results for bottomonium at nonzero temperature obtained using NRQCD on Fastsum Generation 2L ensembles, as part of the Fastsum collaboration's programme to determine the spectrum of the bottomonium system as a function of temperature using a variety of approaches. Here we give an update on results for spectral functions obtained using Kernel Ridge Regression. We pay in particular attention to the generation of training data and introduce the notion of using lattice QCD ensembles to learn how to improve the generation of training data. A practical implementation is given.

    hep-latnucl-thPoS(2022)·12 citations
14. 14*

    HMC with Normalizing Flows

    Sam Foreman🇺🇸 · Taku Izubuchi🇺🇸 · Luchang Jin🇺🇸 · Xiao-Yong Jin🇺🇸 · James C. Osborn🇺🇸 · Akio Tomiya🇺🇸

    We propose using Normalizing Flows as a trainable kernel within the molecular dynamics update of Hamiltonian Monte Carlo (HMC). By learning (invertible) transformations that simplify our dynamics, we can outperform traditional methods at generating independent configurations. We show that, using a carefully constructed network architecture, our approach can be easily scaled to large lattice volumes with minimal retraining effort. The source code for our implementation is publicly available online at https://github.com/nftqcd/fthmc.

    ↳ cs.LGhep-latPoS(2022)·35 citations
15. 15*

    Quantum speed limit and stability of coherent states in quantum gravity

    Klaus Liegener🇩🇪 · Łukasz Rudnicki🇵🇱

    Utilizing the program of expectation values in coherent states and its recently developed algorithmic tools, this letter investigates the dynamical properties of cosmological coherent states for Loop Quantum Gravity. To this end, the Quantum Speed Limit is adapted to Quantum Gravity, yielding necessary consistency checks for any proposal of stable families of states. To showcase the strength of the developed tools, they are applied to a prominent model: the Euclidean part of the quantum scalar constraint. We report the variance of this constraint evaluated on a family of coherent states showing that, for short times, this family passes the Quantum Speed Limit test, allowing the transition from one coherent state to another one.

    ↳ gr-qchep-latquant-phClass.Quant.Grav.(2022)·7 citations
16. 16*

    Polarized Gluon Pseudodistributions at Short Distances

    Ian Balitsky🇺🇸 · Wayne Morris🇺🇸 · Anatoly Radyushkin🇺🇸

    We formulate the basic points of the pseudo-PDF approach to the lattice calculation of polarized gluon PDFs. We present the results of our calculations of the one-loop corrections for the bilocal $G_{\mu \alpha }(z){\tilde{G}}_{\lambda \beta }(0)$ correlator of gluonic fields. Expressions are given for a general situation when all four indices are arbitrary, and also for specific combinations of indices corresponding to three matrix elements that contain the twist-2 invariant amplitude related to the polarized PDF. We study the evolution properties of these matrix elements, and derive matching relations between Euclidean and light-cone Ioffe-time distributions. These relations are necessary for extraction of the polarized gluon distributions from the lattice data.

    ↳ hep-phhep-latJHEP(2022)·20 citations
17. 17*

    Bootstrapping $N_f=4$ conformal QED${}_3$

    Soner Albayrak🇺🇸 · Rajeev S. Erramilli🇺🇸 · Zhijin Li🇺🇸 · David Poland🇺🇸 · Yuan Xin🇺🇸

    We present the results of a conformal bootstrap study of the presumed unitary IR fixed point of quantum electrodynamics in three dimensions (QED${}_3$) coupled to $N_f=4$ two-component Dirac fermions. Specifically, we study the four-point correlators of the $SU(4)$ adjoint fermion bilinear $r$ and the monopole of lowest topological charge ${\mathcal{M}}_{1/2}$. Most notably, the scaling dimensions of the fermion bilinear $r$ and the monopole ${\mathcal{M}}_{1/2}$ are found to be constrained into a closed island with a combination of spectrum assumptions inspired by the $1/N_f$ perturbative results as well as a novel interval positivity constraint on the next-lowest-charge monopole ${\mathcal{M}}_1$. Bounds in this island on the $SU(4)$ and topological $U(1{)}_t$ conserved current central charges $c_J$, $c_J^t$, as well as on the stress tensor central charge $c_T$, are comfortably consistent with the perturbative results. Together with the scaling dimensions, this suggests that a part of estimates from the $1/N_f$ expansion -- even at $N_f=4$ -- provide a self-consistent solution to the bootstrap crossing relations, despite some of our assumptions not being strictly justified.

    ↳ hep-thcond-mat.stat-mechcond-mat.str-elhep-latPRD(2022)·57 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.