中国格点QCD第一届年会

30 Oct 2021, 08:00 → 2 Nov 2021, 18:00 Asia/Shanghai

线上

Chuan Liu (School of Physics, Peking University) , Guoming Liu (South China Normal University) , Heng-Tong Ding (Central China Normal University) , Jian Liang (华南师范大学) , Liuming Liu (Institute of Modern Physics, CAS) , Ming Gong, Wei Wang (Shanghai JiaoTong University) , Xu Feng (Peking University) , Yi-Bo Yang (ITP/CAS) , Ying Chen (IHEP) , Zhaofeng LIU (Institute of High Energy Physics, CAS) , 佳俊 吴 (University of Chinese Academy of Sciences) , 鹏 孙 (Nanjing Normal University)

“中国格点QCD第一届年会”将于2021年10月30日-11月2日在线上举办，华南师范大学承办，会议注册已经开放，会议报告均为邀请报告。

强相互作用的非微扰性质是标准模型中尚待解决的重大理论疑难，也是其精细检验的迫切实践需要。从第一性原理出发，格点QCD能够利用超大规模数值模拟，精确计算上述非微扰性质，并与目前和未来的实验结果相互印证。

中国于20世纪八十年代初开始格点QCD研究，并于2005年成立了合作组CLQCD。经过多年发展和近期一大批优秀年轻研究人员的加盟，中国的格点QCD研究已经具备了利用最顶尖的超级计算机，探索强子能谱、核子结构、QCD相结构和标准模型精细检验等方向的国际前沿问题的能力。

近年来我国的大型超算的计算能力在国际上取得了很好的排名，并且我国正在规划建设更高性能的E级超算，这对中国格点QCD的发展是一个极大的机遇。同时，华南师范大学、中科院近物所、中科院理论物理所、中科院高能所、华中师范大学、湖南师范大学等机构以及科技部重点研发专项和中科院战略先导专项的鼎力支持，也为中国的格点QCD研究提供了重要的计算资源。

因此，自今年起中国格点QCD将每年举办年会，邀请相关领域专家共同探讨格点QCD的最新进展以及粒子物理、核物理中的重要物理问题，对中国格点QCD的发展提出建议，并寻求格点QCD与相关领域的合作与协同发展。

 

会议使用腾讯会议，会议链接如下：

Meeting Topic: 中国格点QCD第一届年会
Meeting Time: 2021/10/30-2021/11/02 08:00-19:00(GMT+08:00) China Standard Time - Beijing, Daily

Click the link to join the meeting or to add it to your meeting list:
https://meeting.tencent.com/dm/N36zBW7eyoG4

Meeting ID: 554 9789 1248

Saturday, 30 October

09:00 → 11:50 session1

Convener: Dr Jian-Ping Ma (Institute of Theoretical Physics, CAS, Beijing)

09:00 开幕致辞

Speaker: Prof. 恩科 王

09:10 开幕致辞

Speaker: Prof. Yifang Wang (高能所)

09:20 中国格点量子色动力学的历史、现状和未来

Speaker: Prof. 川 刘 (北京大学物理学院)

Slides lattice2021-China.pdf

10:00 Break

10:10 Challenges in computing partons on lattice

EIC in China will primarily probe parton physics in a high-energy proton or nucleus. However, computing partons on lattice is a difficult task and may take years to get high precisions. In this talk, I will consider a number of key factors which one must control to get reliable calculations, which include renormalization of linear divergences, taking continuum limit, creating large momentum states, and perturbative matching to higher-orders. Some progress in these areas will be discussed.

Speaker: Prof. 向东 季

10:50 Electron Ion Collider in China (EicC)

Lepton scattering is an established ideal tool for studying inner structure of small particles such as nucleons as well as nuclei. As a future high energy nuclear physics project, an Electron-ion collider in China (EicC) has been proposed. It will be constructed based on an upgraded heavy-ion accelerator, High Intensity heavy-ion Accelerator Facility (HIAF) which is currently under construction, together with an additional electron ring. The proposed collider will provide highly polarized electrons (with the polarization ~80%), protons and Helium-3 (both with the polarization ~70%), as well as unpolarized ion beams from Carbon to Uranium with viable center of mass energy from 10 to 20 GeV and the luminosity of (2 ~ 4) $\times$ 10$^{33}$ cm$^{−2}$∙s$^{−1}$. The main foci of the EicC will be the precision measurements of the structure of proton in the sea quark region, including 3D tomography of nucleon which reveals the QCD dynamics; the partonic structure of nuclei and the parton interaction with the nuclear environment, in particular, the short range correlation of nucleons and the cold nuclear matter effects; the exotic states, especially those with heavy flavor quark contents. In addition, issues fundamental to understanding the origin of mass could be addressed by measurements of heavy quarkonia near-threshold production at the EicC. In order to achieve the above-mentioned physics goals, a hermetical detector system will be constructed with the cutting-edge technology. In this talk, the physics program, detector conceptual design and the project status will be reported.

Speaker: Prof. 宇翔 赵 (中国科学院近代物理研究所)

Slides Yuxiang_EicC.pdf

11:20 新一代神威超算应用支撑系统

基于最新自主软硬件技术构建的新一代神威超算系统，再一次成为高性能计算领域国之重器的重要代表，为海洋科学、航空航天、生物医药、新能源、新材料、大数据、人工智能等领域提供超强的计算能力及应用服务。报告简要介绍为应对大规模应用的挑战性问题，构建可持续发展的国产高性能计算应用生态，新一代神威超算在应用支撑体系方面做的努力和成效。

Speaker: 芳 李

14:00 → 18:00 session2

Convener: Prof. 川 刘 (北京大学物理学院)

14:00 Recent results from BESIII experiment

BESIII is an experiment running at tau-charm energy region at the Beijing Electron Positron Collider (BEPCII). Since the first data taking in 2009, BESIII has accumulated the world’s largest data samples of D and Ds meson decays, 10 billion J/ψ and 2.7 million ψ(3686) events, and about 100 million events with center-of-mass energy between 4 and 4.9 GeV for studies of nonstandard hadrons and the Λc. In this talk, the most recent results on the exotic charmoniumlike XYZ states, light hadron spectroscopy, the weak decays of the charmed hadrons will be reported. The measurements where lattice QCD calculations are needed will be be emphasized.

Speaker: Prof. Beijiang LIU (高能所)

Slides BESIII_Beijiang.pdf

14:30 Bridging lattice QCD to experiments using effective field theory for hadron spectroscopy

Speaker: Prof. Feng-Kun Guo (ITP, CAS)

Slides LatticeCN2021_Guo.pdf

15:00 Hadron spectroscopy on the lattice

This is a brief review of lattice studies on hadron spectroscopy in China. The opportunities and challenges will be discussed also.

Speaker: Prof. 莹 陈 (高能所)

Slides CLQCD2021.pdf

15:30 Hadron structure in China

I will briefly review the history and status of the lattice QCD calculation of the hadron structure in China, and discuss the present plan to reach the next milestone.

Speaker: Prof. Yi-Bo Yang (ITP/CAS)

Slides 2021.10.30.pdf

16:00 Scientific opportunities and Computing challenges in Hot & Dense Lattice QCD

Speaker: Prof. Heng-Tong Ding (Central China Normal University)

Slides HTD_LQCD_guangzhou.pdf

16:30 Lattice QCD and high intensity frontiers

Speaker: Prof. 旭 冯 (Peking University)

Slides LQCD_High_Intensity.pdf

17:00 面向国产超算的格点QCD软件系统前瞻

Speaker: Prof. 明 宫

Sunday, 31 October

09:00 → 12:30 session3

Convener: Dr Feng-Kun Guo (ITP, CAS)

09:00 What can Lattice QCD provide for Hadron Spectroscopy

Lattice QCD is one of the most important tool to study hadron physics. The key point by using lattice QCD results to study hadron physics is to transfer lattice QCD spectrum to the observables. The famous Luscher equation provides a powerful method to connect them. We also develop an alternative method, named as Hamiltonian Effective Field Theory (HEFT) method. In this talk we will introduce it and relevant recent researches. Once we have the link between Lattice QCD result and the observables, there are two questions, what we need from the lattice QCD and what can we learn from Lattice QCD? In this talk , I want to make some discussions.

Speaker: Prof. 佳俊 吴 (University of Chinese Academy of Sciences)

Slides wujiajun@ucas.ac.cn

09:30 Lorentz invariant 3-body quantization condition in Lattice QCD

The three-particle quantization condition on the lattice is written down in a manifestly relativistic-invariant form by using a generalization of the non-relativistic effective field theory (NREFT) approach. A partial diagonalization of the quantization condition into the various irreducible representations of the (little groups of the) octahedral group has been carried out both in the center-of-mass frame and in moving frames. Furthermore, producing synthetic data in a toy model, the relativistic invariance is explicitly demonstrated for the three-body bound state spectrum.

Speaker: 锦毅 庞 (University of Shanghai of Science and Technology)

10:00 The study of pseudoscalar glueball on Lattice QCD

Speaker: Prof. 龙成 桂 (Hunan Normal University)

Slides the_study_of_pesudoscalar_glueball_on_lattice_qcd.pdf

10:30 Finite-volume and finite-tempetature effects in chiral effective field theory

Speaker: Prof. 志辉 郭 (东南大学)

Slides guo-2021-lattciechina.pdf

11:00 Most charming dibaryon

A pair of triply charmed baryons, $Ω_{ccc}Ω_{ccc}$, is studied as an ideal dibaryon system by $(2+1)$-flavor lattice QCD with nearly physical light-quark masses and the relativistic heavy quark action with the physical charm quark mass. The spatial baryon-baryon correlation is related to their scattering parameters on the basis of the HAL QCD method. The $Ω_{ccc}Ω_{ccc}$ in the $^1S_0$ channel taking into account the Coulomb repulsion with the charge form factor of $Ω_{ccc}$ leads to the scattering length $a^C_0\simeq−19$ fm and the effctive range $r^C_{\text{eff}}\simeq0.45$ fm. The ratio $r^C_{\text{eff}}/a^C_0\simeq$−0.024, whose magnitude is considerably smaller than that of the dineutron $(−0.149)$, indicates that $Ω_{ccc}Ω_{ccc}$ is located in the unitary regime.

Speaker: Yan Lyu (s)

11:20 Possibility of Glueball at Physical Point

We perform an exploratory study of glueballs on two RBC/UKQCD gauge ensembles with the $N_f=2+1$ physical quark masses at two lattice spacings. The statistical uncertainties of the glueball correlation functions are considerably reduced through the cluster decomposition error reduction (CDER) method. The Bethe-Salpeter wave functions are obtained for the scalar, tensor and pseudoscalar glueballs by using the spatially extended glueball operators defined through the gauge potential $A_\mu(x)$ in the Coulomb gauge. These wave functions show similar features of non-relativistic two-gluon systems, and then are used to optimize the signals of the related correlation functions at the early time region and the ground state masses can be extracted precisely thereafter. By the assumptions that the glueball operators defined in terms gauge potentials couple almost exclusively to pure glueball states, the obtained masses are interpreted to be those of the ground state pure gauge glueballs. Our result shows the \red{possibility} of glueball states in the presence of dynamical quarks, even though many systematic uncertainties have not yet be well tackled with.

Speaker: 飞宇 陈

11:40 Lattice QCD study of multi-quark states

Speaker: Prof. Liuming Liu (Institute of Modern Physics, CAS)

Slides multiquarkstates.pdf

14:00 → 17:50 session4

Convener: 旭 冯 (Peking University)

14:00 Weak Decays of Charmed Baryons from LQCD

Speaker: Prof. Wei Wang (Shanghai JiaoTong University)

14:30 Valence parton distribution of pion from lattice QCD at physical point

We present the first lattice calculation of pion valence parton distribution using matching formula at NNLO level. We use the Wilson-Clover fermion on three 2+1 flavor HISQ ensembles of lattice spacings a = 0.04, 0.06 and 0.076 fm, with two pion mass including the physical one. Two unitary Domain-Wall calculations at physical point are also presented. This allows us to control the continuum limit, quark mass effects as well as the chiral symmetry. Our analysis use ratio-based schemes to renormalize the equal-time bilocal quark-bilinear matrix elements. We extract first few moments model independently and reconstruct the x-dependent PDF.

Speaker: Dr 翔 高

15:00 Proton momentum and angular momentum decompositions with overlap fermions

Speaker: Dr Gen Wang (University of Kentucky)

Slides Gen_Wang_2021.pdf

15:30 Lattice QCD Calculation of TMD Soft Function Through Large-Momentum Effective Theory

Speaker: Dr 其安 张 (Shanghai Jiao Tong University)

Slides Qi-An_Zhang.pdf

16:00 Distribution amplitudes from lattice QCD

We present the first lattice QCD calculation of the distribution amplitudes of longitudinally and transversely polarized vector mesons K∗ and φ using large momentum effective theory. We use the clover fermion action on three ensembles with 2+1+1 flavors of highly improved staggered quarks (HISQ) action, generated by MILC collaboration, at physical pion mass and {0.06, 0.09, 0.12} fm lattice spacings, and choose three different hadron momenta Pz = {1.29,1.72,2.15} GeV. The resulting lattice matrix elements are nonperturbatively renormalized in a hybrid scheme proposed recently. Also an extrapolation to the continuum and infinite momentum limit is carried out. We find that while the longitudinal distribution amplitudes tend to be close to the asymptotic form, the transverse ones deviate rather significantly from the asymptotic form. Our final results provide crucial ab initio theory inputs for analyzing pertinent exclusive processes.

Speaker: Dr 俊 华 (Shanghai Jiao Tong University)

Slides huajun.pdf

16:30 Collins-Soper kernel from transverse momentum-dependent wave functions in LaMET

In this work we present the transversity $b_{\perp}$-dependence Collins-Soper kernel extracted from pion transverse momentum dependent wave functions in the framework of large momentum effective theory from lattice QCD. We use clover fermion action with $2 + 1 + 1$ flavors of highly improved staggered quarks (HISQ), generated by MILC Collaboration. A single ensemble is used, with lattice spacing $a=0.12$fm and volume as $L^3\times T=48^3\times64$. The results are presented based on pion mass $M_{\pi}=670$MeV, and three hadron momenta as $P^z = 2\pi/L\times\{8, 10, 12\} = \{1.72, 2.15, 2.58\}$GeV. The result of Collins-Soper kernel is determined of joint fit through momentum pairs.

Speaker: 旻寰 楚 (Shanghai Jiao Tong University)

Slides Min-Huan_Chu.pdf

16:50 Correlated Dirac Eigenvalues and Axial Anomaly in Chiral Symmetric QCD

In this talk I will present the novel relations between the quark mass derivatives [$\partial^n \rho(\lambda,m_l)/\partial m_l^n$] of the Dirac eigenvalue spectrum and the $(n+1)$-point correlations among the eigenvalues. Using these relations we present lattice QCD results for $\partial^n \rho(\lambda,m_l)/\partial m_l^n$ ($n=1, 2, 3$) for $m_l$ corresponding to pion masses $m_\pi=160-55~$MeV, and at a temperature of about 1.6 times the chiral phase transition temperature. Calculations were carried out using (2+1) flavors of highly improved staggered quarks with the physical value of strange quark mass, three lattice spacings $a=0.12, 0.08, 0.06$~fm. We find that $\rho(\lambda\to0,m_l)$ develops a peaked structure. This peaked structure arises due to non-Poisson correlations within the infrared part of the Dirac eigenvalue spectrum, becomes sharper as $a\to0$, and its amplitude is proportional to $m_l^2$. We demonstrate that this $\rho(\lambda\to0,m_l)$ is responsible for the manifestations of axial anomaly in two-point correlation functions of light scalar and pseudoscalar mesons. After continuum and chiral extrapolations we find that axial anomaly remains manifested in two-point correlation functions of scalar and pseudoscalar mesons in the chiral limit. This talk is based on PRL 126 (2021) 082001.

Speaker: Dr 瑜 张

Slides CLQCD_YuZhang.pdf

Monday, 1 November

09:00 → 11:50 session5

Convener: Liuming Liu (Institute of Modern Physics, CAS)

09:00 Renormalization and extrapolation strategies for parton physics from lattice QCD

Speaker: Prof. Jianhui Zhang (Beijing Normal University)

09:30 Lattice calculation powered by factorization theory

Speaker: Prof. Yan-Qing Ma (Peking University)

Slides YQMa20211101.pdf

10:00 DSEs meet LQCD: foundations of EHM

Speaker: Prof. 雷 常 (Nankai University)

10:30 The contribution of QCD trace anomaly to hadron mass

We present the first Lattice QCD calculation of the quark and gluon trace anomaly contributions to the hadron masses, using the overlap fermion on the 2+1 flavor dynamical Domain wall quark ensemble. The result shows that the gluon trace anomaly contributes to most of the nucleon mass, and the contribution in the pion state is smaller than that in others.

Speaker: Dr HE Fangcheng

11:00 Flavor contents of the vacuum from the Dirac spectrum of overlap fermions

Speaker: Prof. Jian Liang (华南师范大学)

Slides Dirac_Spectrum_CLQCD.pdf

11:30 Transverse Momentum Dependent PDF Calculation

Speaker: 宇杰 潘 (N)

14:00 → 18:00 session6

Convener: Prof. Heng-Tong Ding (Central China Normal University)

14:00 QCD at finite temperature and density within functional renormalization group approach

In this talk, I would like to discuss recent progress in studies of QCD at finite temperature and densities within the functional renormalization group (fRG) approaches, e.g., the QCD phase structure, QCD equation of state, baryon number fluctuations, spectral functions, real-time dynamics, etc. The relevant results are compared with those obtained from recent lattice simulations. The fRG is a nonperturbative continuum field theory, which is well suited for computation of QCD thermodynamics. Quantum, thermal and density fluctuations are encoded successively through running of the renormalization group scale in the fRG approach.

Speaker: Prof. 伟杰 付 (大连理工大学)

Slides Wei-jie-FU-lattice202111.pdf

14:30 Study the QCD Phase Structure via RHIC Beam Energy Scan

Speaker: Prof. Xiaofeng Luo (Central China Normal University)

Slides XFLUO_20211101.pdf

15:00 Quarkonia and heavy quark diffusion in the hot gluonic medium

In this talk I will report our recent lattice calculations on the heavy quark diffusion in the hot medium. The calculations are carried out in the quenched approximation on large, fine, isotropic lattices. The quark masses cover physical charm quark mass, physical bottom quark mass and infinite heavy quark mass.

Speaker: Dr Hai-Tao Shu (R)

Slides Hai-Tao_Shu.pdf

15:30 Fluctuations of conserved charges in strong magnetic fields

We present results on the second-order fluctuations of and correlations among net baryon number, electric charge, and strangeness in (2+1)-flavor lattice QCD in the presence of a background magnetic field. We extended our previous simulations with pion mass $m_\pi=$220 MeV [1] to physical pion mass $m_\pi=140$ MeV. Simulations are performed on $32^3\times8$ lattices using the highly improved staggered fermions with different values of lattice spacing corresponding to temperatures ranging from $144$ MeV to $166$ MeV. The magnetic field strength $eB$ is simulated with 9 different values up to $\sim$40$m_\pi^2$ at each temperature. We discuss the temperature and $eB$ dependences of the second-order fluctuations of and correlations among net baryon number, electric charge, and strangeness. We find that these fluctuations and correlations are substantially affected by the magnetic field at $eB~\sim$15$m_\pi^2$, which is around the strength produced in the initial stage of non-central heavy-ion collisions at the LHC energy. We propose that these fluctuations and correlations could be useful for probing the existence of a magnetic field in heavy-ion collision experiments.

Speaker: Dr Junhong Liu (C)

16:00 Chiral properties of (2+1)-flavor QCD in strong magnetic fields at zero temperature

We have performed (2+1)-flavor QCD lattice simulations using the Highly Improved Staggered Quarks (HISQ) action on $N_{\sigma}=32$ and $N_{\tau}=96$ lattices. In our lattice simulations the strange quark mass is fixed to its physical quark mass $m_{s}^{\rm phy}$ and light quark mass is set to $m_{s}^{\rm phy}/10$ which corresponds to $M_{\pi} \approx $ 220 MeV at zero temperature. We have studied the masses and magnetic polarizabilities of light and strange pseudo-scalar mesons, chiral condensates, decay constants of neutral pion and neutral kaon in the presence of background magnetic fields with $eB$ ranging up to around 3.35 GeV$^2$ ($\sim70~M_\pi^2$) in the vacuum. We find that the masses of neutral pseudo-scalar mesons monotonously decrease and then saturate at a nonzero value as the magnetic field strength grows, while there exists a non-monotonous behavior of charged pion and kaon masses as magnetic field grows. We observe a $qB$ scaling of the up and down quark flavor components of neutral pion mass, neutral pion decay constant as well as the quark chiral condensates in the magnetic field strength window (0.05GeV$^2$, 3.35 GeV$^2$). We show that the correction to the Gell-Mann-Oakes-Renner relation involving neutral pion is less than 6\%, and the correction for the relation involving neutral kaon is less than 30\% as $eB$ up to 3.35 GeV$^2$. The validity of 2-flavor GMOR suggests that neutral pion is still the Goldstone boson, the mass reduction of neutral pion explains the reduction of the critical temperature of chiral symmetry breaking. And we further find that the reconciliation of magnetic catalysis and reduction of pion mass intrinsically lies in the Ward identity. This talk is based on Phys.Rev.D 104 (2021) 1, 014505.

Speaker: Dr Sheng-Tai Li (CCNU)

Slides LAT21_china.key

16:30 lattice ensemble generation with clover action

Speaker: Prof. 鹏 孙 (Nanjing Normal University)

Slides configuration.pptx

Tuesday, 2 November

09:00 → 12:10 session7

Convener: Yi-Bo Yang (ITP/CAS)

09:00 Lattice calculation of the muon g-2

Speaker: Prof. Luchang Jin (University of Connecticut)

Slides muon-g-2-luchang.pdf

09:30 Lattice calculation of the $K_L$ and $K_S$ mass difference for physical quark masses

The two neutral kaon states in nature, the $K_L$ (long-lived) and $K_S$ (short-lived) mesons, are the two time-evolution eigenstates of the $K^0 - \overline{K^0}$ mixing system. The prediction of their mass difference $\Delta m_K$ based on the standard model is an important goal of lattice QCD. In this talk, I will present the preliminary results from a calculation performed on an ensemble of $64^3 \times 128$ gauge configurations with inverse lattice spacing of 2.36 GeV and physical quark masses. While the statistical error approaches a relatively small size of 9\%, several sources of systematic errors may have more significant effects. In this talk I will also address studies performed on smaller lattices to estimate the systematic errors in our result.

Speaker: Dr Bigeng Wang (U)

Slides CLQCD_talk_11022021.pdf

10:00 格点场论研究早期宇宙对称性破缺

Speaker: Prof. 立功 边 (重庆大学)

Slides PMFGW_FOPT1102.pdf

10:30 Charmonia Decays on the Lattice

The charmonia decays present an ideal laboratory for testing the interplay between perturbative and nonperturbative QCD. In this talk, I focus on the all-photon decay and radiative decay of charmoina. Adopting a new method proposed recently, we perform the systematic lattice calculations on ηc/χc0→2γ and J/ψ→γηc. By using three Nf=2 twisted mass gauge ensembles with different lattice spacings, we obtain the final decay width for these processes. In the end, more interesting charmonia decays are looked forward.

Speaker: Dr 雨 孟 (school of physics Peking Uniersity)

Slides LAT-CHINA21.pdf

11:00 Charm meson decay constants from lattice QCD

Speaker: Prof. Zhaofeng LIU (Institute of High Energy Physics, CAS)

Slides liuzf-CLat21.pdf

11:30 K->lnul'+l'-衰变宽度的格点计算

Speaker: 心宇 脱 (PKU)

11:50 Lattice QCD calculation of the two-photon exchange contribution to the muonic-hydrogen Lamb shift

The measurement of muonic-hydrogen spectroscopy provides the most precise determination of the proton charge radius, where the two-photon exchange contribution plays an important role in the understanding of μH spectroscopy. We will report a lattice QCD calculation of the two-photon exchange contribution by constructing the proton four-point correlation function.

Speaker: 杨 傅 (PKU)

14:00 → 18:00 session8

Convener: Prof. Jian Liang (华南师范大学)

14:00 Recent progress in the construction of covariant chiral nuclear forces

Speaker: Prof. 立升 耿 (Beihang University)

14:30 Nuclear reactions in harmonic-oscillator traps

Speaker: Prof. Bingwei Long (Sichuan University)

15:00 Recent development in lattice effective field theory

Speaker: Prof. 炳楠 吕 (G)

15:30 Quantum Computing Platform for High Energy Physics

Speaker: Dr Yujiang Bi (IHEP)

Slides HEP_QC.pdf

16:00 Lattice QCD gauge configuration generation at near physical point

The solve of Dirac equation for light quarks in lattice QCD suffered from the critical mass slowing down problem, which can be solved by the recently developed multigrid method. In this talk, I will discuss the techniques and algorithms in lattice QCD gauge configuration generation, and combine the HMC and multigrid algorithm to speed up the gauge configuration generation at near physical point.

Speaker: Prof. 玮 孙 (高能所)

Slides WeiSun-HMC-CLQCD2021.pdf

16:30 Machine learning spectral functions in lattice QCD

We study the inverse problem of reconstructing spectral functions from Euclidean correlators via machine learning. We propose a novel neutral network, sVAE, which is based the variational autoencoder (VAE) and can be naturally applied to study the inverse problem. The prominent feature of the sVAE is that a Shannon-Jaynes entropy term having the ground truth values of spectral functions as prior information is included in the loss function to be minimized. We train the network with general spectral functions produced from a Gaussian mixture model. As a test, we use four different types of correlators generated from physically motivated spectral functions made of one resonance peak, a continuum term and perturbative spectral function obtained using non-relativistic QCD. From the mock data test we find that the sVAE in most cases is comparable to the maximum entrop method (MEM) in the quality of reconstructing spectral functions and even outperforms the MEM in the reconstruction of spectral function from pNQRCD. By applying to temporal correlators in the pseudoscalar channel obtained in the quenched lattice QCD at 0.75 $T_c$ on $128^3\times96$ lattices and $1.5$ $T_c$ on $128^3\times48$ lattices, we find that the resonance peak of $\eta_c$ extracted from both the sVAE and MEM has a substantial dependence on the number of points in the temporal direction ($N_\tau$) adopted in the lattice simulation and $N_\tau$ larger than 48 is neeeded to resolve the fate of $\eta_c$ at 1.5 $T_c$.

Speaker: 世阳 陈

16:50 Lattice realization of $\xi$ gauge

We perform a lattice implement of $\xi$ gauge, a more general covariant gauge. We will present the performance of our lattice realization in $\xi$ gauge and primary results of gluon propagators and dynamical overlap quark propagators with $\xi \in [0, 0.2]$. We calculate several renormalization constants under $\xi$ gauge configurations and discuss the gauge invariance under the MS-bar scheme through RI/MOM scheme (perturbative region). We hope this implement provides a new choice to check gauge dependency in numerical calculation.

Speaker: 春江 施

Slides Lattice_realization_of_xi-gauge.pdf

17:10 Propagator generation with Chroma+QUDA for various fermion actions

We will present how to calculate propagators on Chroma with overlap and HISQ (highly improved staggered quark) valence quark, which are not fully supported on Chroma before. For overlap, we setup the fermion action based on polynomials of hwilson action, create overlap dslash on QUDA, migrate Arnoldi algorithm from gwu-code to solve the eigensystem for deflation, and migrate multishift algorithm to calculate propagators with different mass. For HISQ, we write an interface between Chroma and QUDA to put the inversion on GPU and accelerate the calculation. The multigrid algorithm is also used for the HISQ inversion.

Speaker: 宽 张 (ITP)

Slides Propagator_generation_with_Chroma+QUDA_for_various_fermion_actions_.pptx