Tue·Nov 22, 2022Tuesday·November 22, 2022

1. 01*

   Towards symmetric discretization schemes via weak boundary conditions

   Alexander Rothkopf🇳🇴

   The Szymanzik improvement program for gauge theories is most commonly implemented using forward finite difference corrections to the Wilson action. Central symmetric schemes naively applied, suffer from a doubling of degrees of freedom, identical to the well known fermion doubling phenomenon. And while adding a complex Wilson term remedies the problem for fermions, it does not easily transfer to real-valued gauge fields. In this talk I report on recent progress in formulating symmetric discretization schemes for classical actions of simple one-dimensional problems. They avoid doubling by exploiting the weak imposition of initial/boundary conditions. Inspired by recent work in the field of numerical analysis of partial differential equations, I construct a regularized summation-by-parts finite difference operator using boundary data based on affine coordinates. Application to a classical initial value problems with second order derivatives are presented.

   hep-latPoS(2023)·0 citations
2. 02*

   Inverse problems, real-time dynamics and lattice simulations

   Alexander Rothkopf🇳🇴

   The determination of real-time dynamics of strongly coupled quantum fields is a central goal of modern nuclear and particle physics, which requires insight into quantum field theory beyond the weak-coupling approximation. While lattice QCD has provided vital insights into the non-perturbative static properties of quarks and gluons it hides their real-time dynamics behind an ill-posed inverse problem. In this proceeding I will discuss developments in tackling the inverse problem on the lattice and touch upon progress in the direct simualtion of real-time dynamics.

   hep-lathep-phEPJ Web Conf.(2022)·32 citations
3. 03*

   Kernel controlled real-time Complex Langevin simulation

   Daniel Alvestad🇳🇴 · Rasmus Larsen🇳🇴 · Alexander Rothkopf🇳🇴

   This study explores the utility of a kernel in complex Langevin simulations of quantum real-time dynamics on the Schwinger-Keldysh contour. We give several examples where we use a systematic scheme to find kernels that restore correct convergence of complex Langevin. The schemes combine prior information we know about the system and the correctness of convergence of complex Langevin to construct a kernel. This allows us to simulate up to $1.5\beta$ on the real-time Schwinger-Keldysh contour with the $0+1$ dimensional anharmonic oscillator using $m=1,\lambda =24$, which was previously unattainable using the complex Langevin equation.

   hep-latEPJ Web Conf.(2022)·4 citations
4. 04*

   Simulating the Femtouniverse on a Quantum Computer

   Nouman Butt🇺🇸 · Patrick Draper🇺🇸 · Jiayu Shen🇺🇸

   We compute the low-lying spectrum of 4D SU(2) Yang-Mills in a finite volume using quantum simulations. In contrast to small-volume lattice truncations of the Hilbert space, we employ toroidal dimensional reduction to the ``femtouniverse" matrix quantum mechanics model. In this limit the theory is equivalent to the quantum mechanics of three interacting particles moving inside a 3-ball with certain boundary conditions. We use the variational quantum eigensolver and quantum subspace expansion techniques to compute the string tension to glueball mass ratio near the small/large-volume transition point, finding qualitatively good agreement with large volume Euclidean lattice simulations.

   hep-lathep-thquant-phPRD(2023)·6 citations
5. 05*

   The hadronic running of the electroweak couplings from lattice QCD

   Marco Cè🇨🇭 · Antoine Gérardin🇫🇷 · Georg von Hippel🇩🇪 · Harvey B. Meyer🇩🇪 · Kohtaroh Miura🇩🇪 · Konstantin Ottnad🇩🇪 · Andreas Risch🇩🇪 · Teseo San José🇫🇷 · Hartmut Wittig🇩🇪

   The energy dependency (running) of the strength of electromagnetic interactions $\alpha$ plays an important role in precision tests of the Standard Model. The running of the former to the $Z$ pole is an input quantity for global electroweak fits, while the running of the mixing angle is susceptible to the effects of Beyond Standard Model physics, particularly at low energies. We present a computation of the hadronic vacuum polarization (HVP) contribution to the running of these electroweak couplings at the non-perturbative level in lattice QCD, in the space-like regime up to $Q^2$ momentum transfers of $7{\mathrm{GeV}}^2$. This quantity is also closely related to the HVP contribution to the muon $g-2$. We observe a tension of up to $3.5$ standard deviation between our lattice results for $\Delta {\alpha }_{\mathrm{had}}^{(5)}(-Q^2)$ and estimates based on the $R$-ratio for $Q^2$ in the $3$ to $7{\mathrm{GeV}}^2$ range. The tension is, however, strongly diminished when translating our result to the $Z$ pole, by employing the Euclidean split technique and perturbative QCD, which yields $\Delta {\alpha }_{\mathrm{had}}^{(5)}(M_Z^2)=0.02773(15)$. This value agrees with results based on the $R$-ratio within the quoted uncertainties, and can be used as an alternative to the latter in global electroweak fits.

   hep-lathep-phPoS(2022)·0 citations
6. 06*

   Localisation of Dirac eigenmodes and confinement in gauge theories: the Roberge-Weiss transition

   Marco Cardinali🇮🇹 · Massimo D'Elia🇮🇹 · Francesco Garosi🇮🇹 · Matteo Giordano🇭🇺

   Ample numerical evidence from lattice calculations shows a strong connection between the confining properties of gauge theories at finite temperature and the localisation properties of the low-lying Dirac eigenmodes. In this contribution we discuss recent progress on this topic, focussing on results for QCD at imaginary chemical potential ${\mu }_I/T=\pi$ at temperatures above the Roberge-Weiss transition temperature. These confirm the general picture of low modes turning from delocalised to localised at the deconfinement transition, in a previously unexplored setup with a genuine, physical transition in the presence of dynamical fermions. This further supports the use of Dirac eigenmodes as a tool to investigate the mechanisms behind confinement and the deconfinement transition.

   hep-latcond-mat.dis-nnhep-phhep-thEPJ Web Conf.(2022)·0 citations
7. 07*

   QCD mesonic screening masses up to high temperatures

   Mattia Dalla Brida🇨🇭 · Leonardo Giusti🇮🇹 · Tim Harris🇬🇧 · Davide Laudicina🇮🇹 · Michele Pepe🇮🇹

   We discuss a strategy to study non-perturbatively QCD up to very high temperatures by Monte Carlo simulations on the lattice. It allows not only the thermodynamic properties of the theory but also other interesting thermal features to be investigated. As a first concrete application, we compute the flavour non-singlet mesonic screening masses and we present the results of Monte Carlo simulations at 12 temperatures covering the range from T $\sim$ 1 GeV up to $\sim$ 160 GeV in the theory with three massless quarks. On the one side, chiral symmetry restoration manifests itself in our results through the degeneracy of the vector and the axial vector channels and of the scalar and the pseudoscalar ones, and, on the other side, we observe a clear splitting between the vector and the pseudoscalar screening masses up to the highest investigated temperature. A comparison with the high-temperature effective theory shows that the known one-loop order in the perturbative expansion does not provide a satisfactory description of the non-perturbative data up to the highest temperature considered.

   hep-latPoS(2022)·1 citation
8. 08*

   On chiral spin symmetry and the QCD phase diagram

   Owe Philipsen🇩🇪 · Leonid Ya. Glozman🇦🇹 · Peter Lowdon🇩🇪 · Robert D. Pisarski🇺🇸

   Recently, an approximate $SU(4)$ chiral spin-flavour symmetry was observed in multiplet patterns of QCD meson correlation functions, in a temperature range above the chiral crossover. This symmetry is larger than the chiral symmetry of massless QCD, and can only arise effectively when colour-electric quark-gluon interactions dynamically dominate the quantum effective action. At temperatures about three times the crossover temperature, these patterns disappear again, indicating the screening of colour-electric interactions, and the expected chiral symmetry is recovered. In this contribution we collect independent evidence for such an intermediate temperature range, based on screening masses and the pion spectral function. Both kinds of observables behave non-perturbatively in this window, with resonance-like peaks for the pion and its first excitation disappearing gradually with temperature. Using symmetry arguments and the known behaviour of screening masses at small densities, we discuss how this chiral spin symmetric band continues into the QCD phase diagram.

   hep-lathep-phnucl-thPoS(2023)·7 citations
9. 09*

   Efficient quantum implementation of 2+1 U(1) lattice gauge theories with Gauss law constraints

   Christopher Kane🇺🇸 · Dorota M. Grabowska🇨🇭 · Benjamin Nachman🇺🇸 · Christian W. Bauer🇺🇸

   The study of real-time evolution of lattice quantum field theories using classical computers is known to scale exponentially with the number of lattice sites. Due to a fundamentally different computational strategy, quantum computers hold the promise of allowing for detailed studies of these dynamics from first principles. However, much like with classical computations, it is important that quantum algorithms do not have a cost that scales exponentially with the volume. Recently, it was shown how to break the exponential scaling of a naive implementation of a U(1) gauge theory in two spatial dimensions through an operator redefinition. In this work, we describe modifications to how operators must be sampled in the new operator basis to keep digitization errors small. We compare the precision of the energies and plaquette expectation value between the two operator bases and find they are comparable. Additionally, we provide an explicit circuit construction for the Suzuki-Trotter implementation of the theory using the Walsh function formalism. The gate count scaling is studied as a function of the lattice volume, for both exact circuits and approximate circuits where rotation gates with small arguments have been dropped. We study the errors from finite Suzuki-Trotter time-step, circuit approximation, and quantum noise in a calculation of an explicit observable using IBMQ superconducting qubit hardware. We find the gate count scaling for the approximate circuits can be further reduced by up to a power of the volume without introducing larger errors.

   ↳ quant-phhep-lathep-ph42 citations
10. 10*

    Data-based determination of the isospin-limit light-quark-connected contribution to the anomalous magnetic moment of the muon

    Diogo Boito🇧🇷 · Maarten Golterman🇺🇸 · Kim Maltman🇨🇦 · Santiago Peris🇪🇸

    We describe how recent determinations of exclusive-mode contributions to $a_{\mu }^{\mathrm{LO},\mathrm{HVP}}$, the leading-order hadronic vacuum polarization contribution to the anomalous magnetic moment of the muon, can be used to provide, up to small electromagnetic (EM) corrections accessible from the lattice, a data-based dispersive determination of $a_{\mu }^{\mathrm{lqc};\mathrm{IL}}$, the isospin-limit, light-quark-connected contribution to $a_{\mu }^{\mathrm{LO},\mathrm{HVP}}$. Such a determination is of interest in view of the existence of a number of lattice results for this quantity, emerging evidence for a tension between lattice and dispersive determinations of $a_{\mu }^{\mathrm{LO},\mathrm{HVP}}$, and the desire to clarify the source of this tension. Taking as input for the small EM correction that must be applied to the purely data-driven dispersive determination the result $-0.93(58)\times 10^{-10}$ obtained in a recent BMW lattice study, we find $a_{\mu }^{\mathrm{lqc};\mathrm{IL}}$ to be $635.0(2.7)\times 10^{-10}$ if the results of Keshavarzi, Nomura and Teubner are used for the exclusive-mode contributions and $638.4(4.1)\times 10^{-10}$ if instead those of Davier, Höcker, Malaescu and Zhang are used.

    ↳ hep-phhep-latPRD(2023)·19 citations
11. 11*

    Impact of Lattice Strangeness Asymmetry Data in the CTEQ-TEA Global Analysis

    Tie-Jiun Hou🇨🇳 · Huey-Wen Lin🇺🇸 · Mengshi Yan🇨🇳 · C.-P. Yuan🇺🇸

    We study the impact of lattice data on the determination of the strangeness asymmetry distribution $s_{-}(x)\equiv s(x)-\bar{s}(x)$ in the general CTEQ-TEA global analysis of parton distribution functions (PDFs) of the proton. Firstly, we find that allowing a nonvanishing $s_{-}(x)$, at the initial $Q_0=1.3$~GeV scale, in a global PDF analysis leads to a CT18As fit with similar quality to CT18A. Secondly, including the lattice data in the CT18As\_Lat fit greatly reduces the $s_{-}$-PDF error band size in the large-$x$ region. To further reduce its error would require more precise lattice data, extended to smaller $x$ values. We take ATLAS 7 TeV $W$ and $Z$ production data, SIDIS di-muon production data, $F_3$ structure function data, E866 NuSea data, and E906 SeaQuest data as examples to illustrate the implication of CT18As and CT18As\_Lat fits. The parametrization dependence for PDF ratio $(s+\bar{s})/(\bar{u}+\bar{d})(x)$ is analyzed with CT18As2 and CT18As2\_Lat fits as results.

    ↳ hep-phhep-latPRD(2023)·30 citations
12. 12*

    The Future of US Particle Physics -- The Snowmass 2021 Energy Frontier Report

    Meenakshi Narain · Laura Reina · Alessandro Tricoli · Michael Begel · Alberto Belloni · Tulika Bose · Antonio Boveia · Sally Dawson · Caterina Doglioni · Ayres Freitas · James Hirschauer · Stefan Hoeche and 23 other authors

    This report, as part of the 2021 Snowmass Process, summarizes the current status of collider physics at the Energy Frontier, the broad and exciting future prospects identified for the Energy Frontier, the challenges and needs of future experiments, and indicates high priority research areas.

    ↳ hep-exhep-lathep-phhep-th+196 citations
13. 13*

    Strongly Interacting Dark Matter from $Sp(4)$ Gauge Theory

    Fabian Zierler🇦🇹 · Suchita Kulkarni🇦🇹 · Axel Maas🇦🇹 · Seán Mee🇦🇹 · Marco Nikolic🇦🇹 · Josef Pradler🇦🇹

    The stable hadronic bound states in a hidden new non-Abelian gauge sector provide interesting candidates for strongly-interacting Dark Matter (DM). A particular example are theories in which DM is made up of dark pions which set the DM relic abundance through self-annihilation. One of the simplest realizations is $Sp(4{)}_c$ gauge theory with two Dirac fermions. We discuss its mesonic multiplets for degenerate and non-degenerate fermions, construct a low-energy effective theory and present lattice results for the pseudoscalar mesons and vector mesons.

    ↳ hep-phhep-latEPJ Web Conf.(2022)·15 citations
14. 14*

    $|V_{cb}|$, LFU and $SU(3{)}_F$ symmetry breaking in $B_{(s)}\to D_{(s)}^{(\ast )}\ell {\nu }_{\ell }$ decays using Lattice QCD and Unitarity

    Guido Martinelli🇮🇹 · Manuel Naviglio🇮🇹 · Silvano Simula🇮🇹 · Ludovico Vittorio🇫🇷

    We present an application of the unitarity-based dispersion matrix (DM) approach to the extraction of the CKM matrix element $|V_{cb}|$ from the experimental data on the exclusive semileptonic $B_{(s)}\to D_{(s)}^{(\ast )}\ell {\nu }_{\ell }$ decays. The DM method allows to achieve a non-perturbative, model-independent determination of the momentum dependence of the semileptonic form factors. Starting from lattice results available at large values of the 4-momentum transfer and implementing non-perturbative unitarity bound, the behaviour of the form factors in their whole kinematical range is obtained without introducing any explicit parameterization of their momentum dependence. We consider the four exclusive semileptonic $B_{(s)}\to D_{(s)}^{(\ast )}\ell {\nu }_{\ell }$ decays and extract $|V_{cb}|$ from the experimental data for each transition. The average over the four channels is $|V_{cb}|=(41.2\pm 0.8)\cdot 10^{-3}$, which is compatible with the latest inclusive determination at $1\sigma$ level. We address also the issue of Lepton Flavour Universality by computing pure theoretical estimates of the $\tau /\ell$ ratios of the branching fractions for each channel, where $\ell$ is a light lepton. In the case of a light spectator quark we obtain $R(D^{\ast })=0.275(8)$ and $R(D)=0.296(8)$, which are compatible with the corresponding experimental values within $1.3\sigma$. In the case of a strange spectator quark we obtain $\text{R}(D_s^{\ast })=0.2497(60)$ and $\text{R}(D_s)=0.298(5)$. The different values for $R(D_s^{\ast })$ and $R(D^{\ast })$ may reflect $SU(3{)}_F$ symmetry breaking effects, which seem to be present in some of the lattice form factors, especially at large values of the recoil.

    ↳ hep-phhep-exhep-latPoS(2022)·2 citations
15. 15*

    Chiral instabilities & the fate of chirality imbalance in non-Abelian plasmas

    Sören Schlichting🇩🇪 · Sayantan Sharma🇮🇳

    We present a first principles study of chiral plasma instabilities and axial charge transfer in non-Abelian plasmas with a strong gauge-matter coupling $g^2{N}_f=64$, by performing $3+1$ D real-time classical-statistical lattice simulation with dynamical fermions. We explicitly demonstrate for the first time that -- unlike in an Abelian plasma -- the transfer of chirality from the matter sector to the gauge fields occurs predominantly due to topological sphaleron transitions. We elaborate on the similarities and differences of the axial charge dynamics in cold Abelian $U(1)$ and non-Abelian $SU(2)$ plasmas, and comment on the implications of our findings for the study of anomalous transport phenomena, such as the chiral magnetic effect in QCD matter.

    ↳ hep-phhep-latnucl-thPRL(2023)·14 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.