International Molecule-type Workshop
Frontiers in Lattice QCD and related topics
April 15 - April 26 2019
Yukawa Institute for Theoretical Physics, Kyoto University

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Tentative Program

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Tentative Timetable of the 1st week (April 15 - 19)

April 15 (Mon.)	April 16 (Tue.)	April 17 (Wed.)	April 18(Thu.)	April 19 (Fri.)
10:00-11:00  Hanlon	10:00-11:00  Colangelo	10:00-11:00  Nemura	9:30-10:30  Yamazaki 10:30-11:00  Doi	10:00-11:00  Takeda
Coffee	Coffee	Coffee	Coffee	Coffee
	11:30-12:00  Hashimoto	11:30-12:30  Hoerz	11:30-12:30  H. Suzuki	11:30-12:00  Ohnishi
	14:15-14:45  Akahoshi	14:00-15:00  Aoki	13:30-14:30  Kikukawa 14:30-15:00  Fukuma	14:00-15:00  Ikeda
15:00-15:30 Coffee	15:00-15:30 Coffee	15:00-15:30 Coffee	15:00-15:30 Coffee	15:00-15:30 Coffee
15:30-16:30  Sasaki	15:30-16:30  YITP colloquium by Koichi Hattori		15:30-16:00  K. Suzuki 16:00-16:30  Rohrhofer 16:30-17:00  Yanagihara
			18:00- Banquet

Tentative Timetable of the 2nd week (April 22 - 26)

April 22 (Mon.)	April 23 (Tue.)	April 24 (Wed.)	April 25(Thu.)	April 26 (Fri.)
9:30-10:00  Fukaya 10:00-11:00  Furuta	10:00-11:00  Feng	10:00-11:00  Walker-Loud	10:00-11:00  Sharpe	10:00-11:00  Rinaldi
Coffee	Coffee	Coffee	Coffee	Coffee
11:30-12:30  Onogi	11:30-12:30  Kaneko	11:30-12:30  Gongyo	11:30-12:00  Nakamura	11:30-12:30  Ohki
	14:00-14:30  Yamamoto	14:00-14:30  Yamanaka	14:00-15:00  Kitazawa	14:00-15:00  Izubuchi
15:00-15:30 Coffee	15:00-15:30 Coffee	15:00-15:30 Coffee	15:00-15:30 Coffee	15:00-15:30 Coffee

Title and Abstract of the talks

• Yutaro Akahoshi  "Study of the $pi pi$ scatterings with the combination of all-to-all propagators and the HAL QCD method"

In this talk, We show recent developments about the combination of all-to-all propagators and the HAL QCD method. We apply the hybrid method for all-to-all propagators, which combines a low-mode spectral decomposition of the quark propagator and noisy estimators for remaining high-modes, to the HAL QCD method, and investigate how potentials are affected by the method systematically through the $I=2$ $pi pi$ scattering calculations with $m_{pi} approx 870 [{ m MeV}]$. We also discuss a preparatory calculation of the $I=1$ $pi pi$ scattering with the hybrid method, which brings us important lessons for future $ ho$ resonance study.

• Sinya Aoki  "Some theoretical issues in the HAL QCD method. "

I will present recent progresses on some theoretical issues in the HAL QCD potential method.

• Gilberto Colangelo  "Two-pion contributions to the muon g-2"

The dispersive approach has been always applied to the calculation of the hadronic vacuum polarization contribution to the muon g-2 and is essential to achieve the very high accuracy with which this is currently calculated. I will discuss our recent calculation of the two-pion contribution to this quantity, which relies on a dispersive description of the pion vector form factor. The dispersive approach to hadronic light-by-light, on the other hand, has been developed only recently, because of its inherent significant difficulties. I will discuss the approach and show numerical results which are also relying on the high-accuracy dispersive description of the pion vector form factor. Recent developments on the role of short distance constraints in hadronic light-by-light will also be discussed.

• Takumi Doi  "Consistency between Luscher's method and HAL method for two-baryon systems on the lattice"

The interactions between two baryons have been studied by two methods in lattice QCD: the direct method and the HAL QCD method. Although the two methods should give the same results theoretically, qualitatively different results have been reported so far. In this talk, we develop a novel method to decompose the two-baryon correlation functions into the finite-volume eigenmodes of the Hamiltonian with the HAL QCD potential (the HAL QCD Hamiltonian), and show that the excited state contaminations in the direct method are responsible for this discrepancy. We also propose an optimized two-baryon operator based on the finite-volume eigenmodes of the HAL QCD Hamiltonian. The finite-volume spectra from temporal correlation function with the optimized operators are found to agree with those from the HAL QCD method. The long-standing issue on the consistency between two methods is thus resolved now: they are consistent with each other quantitatively only if the excited contamination is properly removed in the direct method.

• Xu Feng  "Long-distance processes: from flavor physics to nuclear physics"

TBA

• Hidenori Fukaya  "Why is domain-wall fermion mathematically interesting?"

The Atiyah-Patodi-Singer index theorem describes the bulk-edge correspondence of symmetry protected topological insulators. Recently we showed that the same integer as the APS index can be obtained from the domain-wall Dirac operator. In this talk, we will show the physical motivation of this work, as an introduction to M. Furuta's talk on the mathematical proof that our finding is not a coincidence but generally true.

• Masafumi Fukuma  "Tempered Lefschetz thimble method and its application to strongly correlated electron systems"

Tempered Lefschetz thimble method (TLTM) [arXiv:1703.00861] is a (parallel-)tempering algorithm to solve the sign problem in Monte Carlo simulations. It is implemented on the generalized Lefschetz thimble method (GLTM) by using the flow time of the antiholomorphic gradient flow as a tempering parameter. The TLTM is expected to versatilely solve the dilemma between the sign problem and the multimodal problem, which inherently exists in the GLTM. In this talk, after reviewing the TLTM, we apply the method to the quantum Monte Carlo simulation of the Hubbard model away from half-filling. We show that the TLTM certainly solves the dilemma and gives results that agree nicely with exact values.

• MIKIO FURUTA  "The Atiyah-Patodi-Singer index theorem and domain walls"

We explain a relation between the index for the Atiyah-Patodi-Singer boundary condition for a 2n-dimensional manifold X and a domain wall with corner in the 2n+1 dimensional manifold X x R. Joint work with Hidenori Fukaya, Shinichiroh Matsuo, Tetsuya Onogi, Satoshi Yamaguchi and Mayuko Yamashita.

• Shinya Gongyo  "Decuplet-Decuplet interaction and recent development of partial wave decomposition on lattice"

We will talk about two topics: Decuplet-Decuplet interaction from lattice QCD and a method for partial wave decomposition on lattice. In the first part, we will show Delta-Delta interaction (7S3) in the case of heavy pion mass as well as Omega-Omega interaction (3S0) in the case of nearly physical pion mass. In the second part, we will show a method to approximately extract a component of partial wave expansion on lattice proposed by C. W. Misner. Using this method, we can disentangle l=0,4,6, ..components from A1-projected Nambu-Bethe-Salpeter wave function in the discrete space, so that the superficial fluctuations for its potential is suppressed.

• Andrew Dossin Hanlon  "Progress on the $H$ dibaryon from $N_f = 2 + 1$ CLS ensembles"

Conclusive evidence for the existence of a bound $H$ dibaryon has been lacking since its prediction over forty years ago. Much of the difficulty arises from the expectation of a very small binding energy---based on constraints from the ``NAGARA'' event---if bound at all. Thus, resolving the nature of the $H$ dibaryon will require high precision data. Further, at heavier than physical quark masses the $H$ dibaryon is clearly bound, as determined by multiple lattice QCD calculations, albeit with significant discrepancies for the reported binding energy from different collaborations. To contribute to the resolution of these issues, the Mainz group has made use of the distillation method which has dramatically improved the quality of the energy determinations as compared to using smeared point sources---while retaining a similar computational cost. Here we will report on the progress made from the Mainz group using the $N_f = 2 + 1$ CLS ensembles. Results relevant for channels other than the $H$ dibaryon will also be shown.

• Shoji Hashimoto  "Inclusive processes from lattice QCD(?)"

I describe an idea to calculate inclusive decay rate of B meson.

• Ben Hoerz  "Progress towards nucleon-nucleon interactions with stochastic LapH"

Constraining nucleon-nucleon scattering from lattice QCD poses some challenges. Among those is the breaking of rotational symmetry by the cubic finite volume leading to a mixing of the physical scattering amplitudes. Another technical problem concerns the growth in correlator construction cost in the stochastic LapH method due to the more complicated combinatorics compared to meson-meson systems. This issue can be alleviated by graph-theoretical methods, which also make the construction of three-particle correlation functions more tractable.

• Yoichi Ikeda  "Lattice QCD analysis of charmed tetraquark candidates"

I will present our analysis of tetraquark candidates, Zc(3900), on the basis of the coupled-channel HAL QCD method. Reviewing the experimental observations and several model analyses on the Zc(3900), I present the HAL QCD method and show our results. Finally I will compare the results with the experimental data.

• Taku Izubuchi  "Hadronic contributions to Muon g-2 "

A review on the current progress on the hadronic contributions to muon g-2, including both the hadronic vacuum polarization (HVP) and Hadronic Light-by-light (HLbL), is presented.

• Takashi Kaneko  "B->D(*)��ell��nu decays at non-zero recoils"

We report on our on-going calculation of B->D(*)ell u form factors in lattice QCD with three-flavors of dynamical domain-wall fermions. We also discuss our results' implication to the long-standing tension in the Cabibbo-Kobayashi-Maskawa matrix element |Vcb|.

• Yoshio Kikukawa  "On the gauge-invariant Path-integral measure for the overlap Weyl fermions in 16 of SO(10) / the SM"

We consider the lattice formulations of SO(10) chiral gauge theory with left-handed Weyl fermions in the sixteen dimensional spinor representation 16 within the framework of the Overlap fermion/the Ginsparg-Wilson relation. We define a manifestly gauge-invariant path-integral measure for the left-handed Weyl field using all the components of the Dirac field, but the right-handed part of which is just saturated completely by inserting a suitable product of the SO(10)-invariant 't Hooft vertices in terms of the right-handed field. We also discuss the relations of our formulation to other approaches/proposals to decouple the species-doubling/mirror degrees of freedom. Those include Eichten-Preskill model, Ginsparg-Wilson Mirror-fermion model, Domain wall fermion model with the boundary Eichten-Preskill term, 4D Topological Insulator/Superconductor with gapped boundary phase. We clarify the similarity and the difference in technical detail and show that our proposal is a well-defined testing ground for that basic question.

• Masakiyo Kitazawa  "Stress tensor on the lattice; multi- and single-quark systems, Casimir effect, and etc. "

We perform various lattice numerical simulations with the stress-energy-momentum tensor in SU(3) Yang-Mills theory. The energy-momentum tensor defined through the Yang-Mills gradient flow is used in these analyses. We explore thermodynamics, spatial distribution of stress tensor in quark-anti-quark system, nonzero-temperature Casimir effect, as well as the correlation functions. Extensions of the analysis to other new observables and full-QCD simulations will also be discussed.

• Yoshifumi Nakamura  "Critical endpoints of the finite temperature QCD"

We investigate the critical endpoints of the finite temperature phase transition of QCD at zero chemical potential. We employ the renormalization-group improved Iwasaki gauge action and non-perturbatively $O(a)$-improved Wilson-clover fermion action.

• Hidekatsu Nemura  "Hyperon-Nucleon interaction from lattice quantum chromodynamics at almost physical masses"

We present our recent results of baryon interactions with strangeness $S=-1$ based on Nambu-Bethe-Salpeter (NBS) correlation functions calculated from lattice QCD with almost physical quark masses corresponding to $(m_pi,m_K)approx(146,525)$ MeV and large volume $(La)^4=(96a)^4approx$ (8.1 fm)$^4$. In order to perform a comprehensive study of baryon interactions[1], a large number of NBS correlation functions from NN to $XiXi$ are calculated simultaneously by using large scale computer resources. In this contribution, we focus on the strangeness $S=-1$ channels[2] of the hyperon interactions by means of HAL QCD method. The latest results will be presented. References: [1] H. Nemura, Comput. Phys. Commun. 207, 91 (2016) [arXiv:1510.00903 [hep-lat]]. [2] H. Nemura et al., arXiv:1810.04046 [hep-lat].

• Hiroshi Ohki  "Computing Nucleon Electric Dipole Moment in lattice QCD"

High precision study of nuclear physics is a vital part of searches for new physics beyond the standard model. In particular, observation of permanent electric dipole moments (EDMs) of nucleons (and nuclei) can be direct evidence for violation of CP symmetry. I will briefly review recent progress on lattice calculations of nucleon EDM induced by various CP violating interactions and give some recent preliminary results.

• Akira Ohnishi  "Path optimization for the sign problem in low-dimensional QCD and QCD effective models at finite density"

The sign problem in QCD and its effective models at finite density may be weakened by modifying the integral path (manifold) in the complexified field variable space. We discuss the path optimization to weaken the sign problem in low dimensional QCD and QCD effective models at finite density.

• Tetsuya Onogi  "TKNN formula for general Hamiltonian"

Topological insulators in odd dimensions are characterized by topological numbers. We prove the well-known relation between the topological number given by the Chern character of the Berry curvature and the Chern-Simons level of the low energy effective action for a general class of Hamiltonians bilinear in the fermion with general U(1) gauge interactions including non-minimal couplings by an explicit calculation. A series of Ward-Takahashi identities are crucial to relate the Chern-Simons level to a winding number, which could then be directly reduced to Chern character of Berry curvature by carrying out the integral over the temporal momenta.

• Enrico Rinaldi  "Nuclear matrix elements for baryogenesis"

TBA

• Christian Rohrhofer  "SU(2)_CS and SU(4) symmetry of high temperature QCD"

In this work we investigate the symmetry properties of the hadronic spectrum in high temperature QCD. Spatial isovector correlation functions are caluclated with chiral quarks for temperatures up to 1 GeV. Chiral and U(1) axial symmetry are found to be restored above T_c. An additional SU(2)_CS symmetry is observed within a temperature window. This symmetry is absent in vacuum QCD as well as for non-interacting quarks and could help to understand the effective degrees of freedom above T_c.

• Kenji Sasaki  "Dibaryon search from Lattice QCD"
• Stephen R Sharpe  "Progress on implementing the three-particle quantization condition"

I report on recent work with Tyler Blanton, Raul Briceno, Max Hansen and Fernando Romero-Lopez in deriving and implementing a relativistic model-independent quantization condition for three particles in finite volume.

• Kei Suzuki  "Axial U(1) symmetry in high temperature phase of two-flavor QCD"

In this talk, using lattice QCD simulations with Nf = 2 dynamical fermions by JLQCD Collaboration, I will show our recent results of the observables in the high-temperature phase in which the chiral symmetry is restored, such as the axial U(1) symmetry, topological charge, Dirac eigenvalue spectra, meson correlators, and screening masses. Our gauge ensembles are generated with Moebius domain-wall fermions, but the measurements such as susceptibilities are reweighted to those for the overlap fermions by using overlap/domain-wall reweighting technique. We find that the U(1)A and topological susceptibilities are strongly suppressed in the small quark mass region. We will also discuss the relation between the susceptibilities and meson correlators.

• Hiroshi Suzuki  "Gradient flow and the EMT on the lattice"

TBA

• Shinji Takeda  "Tensor network approach to real-time path integral"

Tensor networks are known as the non-perturbative computational tool for the quantum field theory and its atractive feature is the absence of the sign problem. In my talk, first I give an introductory review of the tensor networks with a focus on the Lagrangian approach. Then I discuss how to numerically evaluate the real-time path integral for 1+1 dimensional lattice scalar field theory by the tensor network approach.

• Andre Walker-Loud  "Understanding the axial structure of the nucleon from QCD"

CalLat has been performing new calculations of the elastic axial structure of the nucleon with the MDWF on gradient-flowed HISQ action. I will present these new preliminary results we are generating and compare to our old results as well as other results in the literature.

• Arata Yamamoto  "Mesons in Magnetic Fields"

I present light meson properties in an external magnetic field, focusing on a charged pion and a charged and polarized rho meson. The magnetic field induces the mass shift and deformation of these mesons. They are studied by the gauge-invariant correlation functions in lattice QCD.

• Nodoka Yamanaka  "Interglueball potential in lattice gauge theory"

Glueballs in SU(N) Yang-Mills theory are good candidates of dark matter. In this talk, we present our result on the calculation of the interglueball potential in SU(2), SU(3), and SU(4) Yang-Mills theories on lattice using the HALQCD method.

• Takeshi Yamazaki  "Direct calculation of two-nucleon energy"

We present a systematic study of the two-nucleon energy calculation at a heavy quark mass in quenched QCD. We compare the effective energy shifts of a two-nucleon channel calculating with the exponential smeared and wall sources, and show that those agree with each other in a region where plateaus for the single-nucleon and two-nucleon correlators are observed. We also discuss the volume dependence of the effective energy shift in the wall source calculation.

• Ryosuke Yanagihara  "Stress tensor distribution around static quarks in hot medium"

We explore the distribution of the energy momentum tensor (EMT) around quark?anti-quark and single quark at nonzero temperature in SU(3) Yang-Mills gauge theory. This is an extension of our previous study [1] on the EMT distribution in static quark?anti-quark systems in vacuum. We discuss the disappearance of the flux tube structure observed in the vacuum simulation. We investigate the total stress acting on the mid-plane between a quark and an anti-quark and show that it agrees with the force obtained from the derivative of the free energy. The color Debye screening effect in the deconfined phase is also discussed in terms of the EMT distribution. [1] R. Yanagihara et al., Phys. Lett. B789 (2019) 210.

Yukawa Institute for Theoretical Physics, Kyoto University
Kitashirakawa Oiwakecho, Sakyo-ku, Kyoto 606-8502 Japan
Contact e-mail: flqcd2019[at]yukawa.kyoto-u.ac.jp