# The 33rd International Symposium on Lattice Field Theory (Lattice 2015)

14-18 July 2015
Kobe International Conference Center
Asia/Tokyo timezone
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# Poster Session

## Place

Location: Kobe International Conference Center
Address: 6-9-1 Minatojima-nakamachi, Chuo-ku, Kobe, Hyogo 650-0046, Japan
Room: 4th floor
Date: 15 Jul 18:30 - 21:00

## Contribution List

Displaying 41 contributions out of 41
Type: Poster Session: Poster Session
Track: Theoretical Developments
We describe a new method to determine in a stochastic fashion the Dirac operator spectral density over the entire range of eigenvalues. This allows for example studies of the chiral limit of the fermion condensate, the mode number and the anomalous mass dimension. We apply this technique to the 2-flavor sextet SU(3) gauge theory, to investigate this theory's viability as a minimal realization of ... More
Presented by Prof. Kieran HOLLAND on 15/07/2015 at 09:30
Type: Poster Session: Poster Session
Track: Nonzero Temperature and Density
We present an accurate computation of the Equation of State of SU(3) Yang-Mills theory using shifted boundary conditions in the temporal direction. In this framework, the entropy density s(T) can be obtained in a simple way from the v.e.v. of the space-time components T_0k of the energy-momentum tensor. Furthermore, contrary to the standard approach, the Equation of State s(T)/T^3 can be measur ... More
Presented by Prof. Leonardo GIUSTI on 15/07/2015 at 09:30
Type: Poster Session: Poster Session
Track: Algorithms and Machines
We present details of our implementation of the Wuppertal adaptive algebraic multigrid code on SIMD architectures, with particular emphasis on the Intel Xeon Phi processor (KNC) used in QPACE 2. As a smoother, the algorithm uses a domain-decomposition-based solver code previously developed for the KNC in Regensburg. We optimized the remaining parts of the multigrid code and conclude that i ... More
Presented by Prof. Tilo WETTIG on 15/07/2015 at 09:30
Type: Poster Session: Poster Session
Track: Algorithms and Machines
The hybrid Monte Carlo (HMC) algorithm has been widely used for dynamical lattice QCD simulations. One of the advantages of using the HMC algorithm is that it is a global algorithm that can update all link variables simultaneously. In this way we can greatly reduce computational cost concerning the fermionic part. We utilize this advantage for parameter estimations of the realized stochastic volat ... More
Presented by Prof. Tetsuya TAKAISHI, Prof. Yubin LIU on 15/07/2015 at 09:30
Type: Poster Session: Poster Session
Track: Nonzero Temperature and Density
At finite density lattice QCD, the famous sign problem has prevented us from studying the QCD phase diagram based on the first-principle calculation. In order to circumvent the problem, we propose a method where we put new wine into old wineskins: i.e., we use an old idea, "canonical approach", but put into it a new ingredient, multi-precision calculations. This is free from the usual limitati ... More
Presented by Prof. Atsushi NAKAMURA on 15/07/2015 at 09:30
Type: Poster Session: Poster Session
Track: Applications Beyond QCD
Around a large charge with atomic number Z > 137, the QED vacuum is expected to collapse due to the strong Coulombic force. While the relativistic quantum mechanics fails to make reliable predictions for the fate of the vacuum, the heavy ion collision experiment also does not give clear understanding of this system. Recently,the "atomic collapse" resonances were observed on graphene where an ... More
Presented by Ms. Aya KAGIMURA on 15/07/2015 at 09:30
Type: Poster Session: Poster Session
Track: Weak Decays and Matrix Elements
We present the Standard Model evaluation of the indirect CP violation parameter $\varepislon_K$ determined using lattice QCD inputs: $\hat{B}_K$, $\xi_0$, $V_{us}$, and $V_{cb}$. We find that the Standard Model prediction of $\varepsilon_K$ with exclusive $V_{cb}$ (lattice QCD results) is lower than the experimental value by $3.6\sigma$. However, this tension disappears with inclusive $V_{cb ... More Presented by Prof. Weonjong LEE on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Standard Model Parameters and Renormalization Preliminary results are presented from a new determination of f_K/f_pi which is based on a series of staggered Nf=2+1+1 simulations in the vicinity of the physical point. Special emphasis is put on the interpolation to the physical point, the finite-volume corrections, the continuum extrapolation and the breaking of the isospin symmetry. Presented by Dr. Stephan DURR on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Hadron Spectroscopy and Interactions Free-form smearing was designed as a way to implement source operators of any desired shape. A variation of the method is introduced that reduces the computational cost by reducing the number of link multiplications to its absolute minimum. Practical utility is demonstrated through calculations of bottomonium and B meson masses. Presented by Richard WOLOSHYN on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Nonzero Temperature and Density In numerical calculation of the lattice QCD, the sign problem of Monte Carlo methods has been a major issue. A numerical renormalization group called tensor renormalization group (TRG) is one of the candidates for the solution of this problem. Grassmann tensor renormalization group (GTRG) is a generalization of the TRG to fermion systems. In this study, We apply the GTRG to the lattice Gross-Ne ... More Presented by Yusuke YOSHIMURA on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Algorithms and Machines We discuss progress and performance from the development of the Grid data parallel interface for cartesian fields of tensor data types. The library is suitable for the simulation of QCD including multiple grids. Wherever appropriate the interface is quite similar to that of QDP++, but the library makes use of C++11 features to reduce the volume of code, compared to QDP++ while bringing gr ... More Presented by Dr. Azusa YAMAGUCHI on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Weak Decays and Matrix Elements We improve heavy-heavy currents for calculating B ̅ →D^((*) ) lν ̅ semi-leptonic form factors with Oktay-Kronfeld (OK) heavy quarks. The OK action, which has dimension 6 and 7 interaction terms, can control the discretization errors of heavy quarks (b and c quarks). The OK action is improved through third order in HQET power counting. We report work on heavy-heavy currents to get the systema ... More Presented by Mr. JAEHOON LEEM on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Theoretical Developments L\"uscher recently introduced Instantaneous Stochastic Perturbation Theory (ISPT) as a method for the stochastic evaluation of lattice perturbation theory. We present an exploratory study of its properties in$\phi^4$theory, and we compare it with both analytical computations and Numerical Stochastic Perturbation Theory. In addition, we propose a automated method based on ISPT for solution of the ... More Presented by Mr. Marco GAROFALO on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Hadron Spectroscopy and Interactions Preliminary results for the effect of open boundary conditions on the masses of glueballs and the probability distributions of glueball correlators, in quenched QCD, are presented. Initial results from glueball correlators computed on unquenched ensembles downloaded from the ILDG data grid are reported. Presented by Dr. Craig MCNEILE on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Chiral Symmetry We present the expansions of the masses of the pseudoscalar mesons in chiral perturbation theory at next-to-leading order for twisted mass lattice QCD with three light quark flavours, taking the mass difference between the up and down quarks into account. Presented by Prof. Gernot MüNSTER on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Algorithms and Machines We are developing a code set "Bridge++" for simulations of lattice gauge theories that aims at an extensible, readable, and portable workbench, while achieving high performance. This work concerns the design of Bridge++ to incorporate the accelerator devices, such as GPUs. As generic frameworks for heterogeneous programming using CPU and accelerator devices, we apply OpenCL and OpenACC to Bridge ... More Presented by Dr. Shinji MOTOKI on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Hadron Spectroscopy and Interactions We study the possible significance of four-quark states in the isosinglet scalar mesons ($J^{PC}=0^{++}$, I=0) by performing two-flavor full lattice QCD simulations on an$8^3 ¥times 16$lattice using the improved gauge action and the clover-improved Wilson quark action. In particular, we evaluate the propagators of molecular and tetraquark operators together with singly disconnected diagrams. In ... More Presented by Mr. Masayuki WAKAYAMA on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Standard Model Parameters and Renormalization We present the quark mass and axial current renormalization factors for the RG-improved gauge and the stout smeared$O(a)$-improved Wilson quark actions. The$O(a)$improvement coefficient for the three-flavors of dynamical quarks has been determined previously with the stout-link smearing parameter$\alpha=0.1, n=6$. We employ the Schr\"{o}dinger functional scheme and obtain the renormali ... More Presented by Mr. Ken-Ichi ISHIKAWA on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Physics Beyond the Standard Model SU2 with Nf=8 is believed to have an infrared conformal fixed point. We use the spectral density method to evaluate the coupling constant dependence of the mass anomalous dimension. We use massless theory with Schrödinger functional boundary conditions and HEX smeared Wilson clover fermions. Presented by Mr. Joni SUORSA on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Theoretical Developments The IIB matrix model has been proposed as a nonperturbative definition of superstring theory. In this work, we study the Euclidean version of this model in which extra dimensions can be dynamically compactified if a scenario of the spontaneous breakdown of the SO(10) rotational symmetry is realized. Monte Carlo calculations of the Euclidean IIB matrix model suffer from a very strong complex action ... More Presented by Prof. Takehiro AZUMA on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Algorithms and Machines The setup cost of a modern solver such as the DD-$\alpha$AMG (Wuppertal Multigrid) is a significant contribution to the total time spent on solving the Dirac equation, and in HMC it can even be dominant. We present an improved implementation of this algorithm with modified computation order in the setup procedure. By processing multiple right-hand sides simultaneously we can alleviate many of the ... More Presented by Mr. Daniel RICHTMANN on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Standard Model Parameters and Renormalization We present the preliminary results of the wave function renormalization factor Z_q and mass renormalization factor Z_m from the bilinear operators obtained using non-perturbative renormalization method(NPR) in the RI-MOM scheme with improved staggered fermions. We use fine ensembles of MILC asqtad lattices (N_f=2+1) with 28^3 \times 96 geometry and am_\ell / am_s = 0.0062 / 0.031. We also prese ... More Presented by Dr. jangho KIM on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Algorithms and Machines We report on our efforts to impliment overlap fermions on NVIDIA GPUs using CUDA, commenting on the algorithms used, implemetation details, and the performance of our code. Presented by Dr. Nigel CUNDY on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Algorithms and Machines Matching factors for the four-fermion operators relevant to B_K are obtained using the Non-Perturbative Renormalization(NPR) method in the RI-MOM scheme. Our NPR codes are calculated in Double Precision(DP) and optimized on Fermi GPU. NVIDIA released The GTX Titan X based on the Maxwell architecture. The Single Precision(SP) calculation performance of the GTX Titan X is improved, but the ratio of ... More Presented by Mr. Jeonghwan PAK on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Algorithms and Machines With the aim of studying the relevance and properties of critical slowing down in Monte Carlo simulations of lattice quantum field theories we carried out a high precision numerical study of the discretised two-dimensional CP^{N-1} model at N=10 using an over-heat bath algorithm. We identify critical slowing down in terms of slowly-evolving topological modes and present evidence that other observa ... More Presented by Dr. Andreas JUETTNER on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Theoretical Developments The 2d CP(N-1) models share a number of features with QCD, like asymptotic freedom, a dynamically generated mass gap, and topological sectors. They have been formulated and analysed successfully in the formalism of the so-called D-theory. In that framework, we propose an experimental set-up for the quantum simulation of the CP(2) model. It is based on ultracold alkaline-earth-atoms located o ... More Presented by Prof. Wolfgang BIETENHOLZ on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Hadron Structure We report a quark spin calculation from the anomalous Ward identity with overlap fermions on 2+1 flavor dynamical fermion configurations. Such a formulation decomposes the divergence of the flavor-singlet axial-vector current into a quark pseudoscalar term and a triangle anomaly term, flavor by flavor. We use the overlap fermion for the valence and the quark loop so that the renormalization consta ... More Presented by Prof. Ming GONG on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Physics Beyond the Standard Model SU(3) gauge theory with eight massless fundamental fermions seems to be near the conformal boundary, and is a candidate of walking technicolor. Along the series of study by LatKMI collaboration using HISQ fermions, S-parameter and vector decay constant, which provide important constraints in the model building, are calculated for this theory. Use of various volumes allows a systematic investigatio ... More Presented by Yasumichi AOKI on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Applications Beyond QCD We study the SU(2) gauge theory with dynamical domain-wall fermions in fundamental and adjoint representations. Dynamical simulations with fundamental fermions are performed with numbers of flavors Nf=2,4,6, and 8. Nf dependence of the meson masses and decay constants are investigated. The same analyses are applied also to the adjoint fermions, based on the investigation of the Aoki phase st ... More Presented by Dr. Hideo MATSUFURU on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Chiral Symmetry We calculate the spectral function of the QCD Dirac operator using the four-dimensional effective operator constructed from the Mobius domain-wall implementation. We utilize the eigenvalue filtering technique combined with the stochastic estimate of the mode number. The spectrum in the entire eigenvalue range is obtained with a single set of measurements. Results on 2+1-flavor ensembles with Mobi ... More Presented by Prof. Shoji HASHIMOTO on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Applications Beyond QCD We employ a strong coupling expansion - similar to the one used in the lattice field theory studies [1] - to solve the one-dimensional extended t-V model of fermions on a lattice [2]. This model is solved for a range of filling factors, including both commensurate - where a charge density wave is present - and incommensurate densities. The first set consists not only of a trivial case of half fill ... More Presented by Mr. Marcin SZYNISZEWSKI on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Theoretical Developments We study the vacuum structure of the SU(3) gauge theory with the flavor number within the conformal region. We perform numerical simulation employing the massless Domain-Wall fermions with the one-step stout smearing. We investigate a conjecture based on the idea of "the conformal field theories with an IR cutoff", which was recently studied using the Wilson fermions. Dealing with the Polyakov l ... More Presented by Dr. Jun NOAKI on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Nonzero Temperature and Density We study the two dimensional nonlinear O(3) model with a chemical potential coupled to the conserved charge. The complex action problem occurring at nonzero chemical potential is solved by means of a duality transform, which yields real and positive weights and makes Monte Carlo simulations feasible. We find a phase transition at the end of a Silver Blaze region, where a net number of particles ap ... More Presented by Mr. Thomas KLOIBER on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Hadron Spectroscopy and Interactions We present first results for I=1 pipi scattering with N_f=2+1+1 twisted mass fermions utilizing the sLapH method. The rho mass and decay width are computed for various pion masses and lattice spacings. Special care was taken in the analysis of systematic uncertainties. Presented by Mr. Markus WERNER on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Theoretical Developments Last year we reported the property of the the Moebius Domain Wall Fermions (MDWF) in the Schroedinger Functional (SF) scheme with the palindromic fifth dimensional parameters and the appropriate boundary operator at the tree-level, and the non-universal behavior for a small fifth direction extent$N_5$. We find that this behavior comes from the residual mass at the tree-level and the universality ... More Presented by Ms. Yuko MURAKAMI on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Vacuum Structure and Confinement We study the static three-quark potential in SU(3) lattice gauge theory at zero temperature with the Polyakov loop correlation function consisting of three Polyakov loops. By employing the multi-level algorithm we overcome the smallness of the signal to noise ratio and obtain remarkably clean signals. We extend our previous investigation of the three-quark potential and compute the potential f ... More Presented by Dr. Miho KOMA on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Physics Beyond the Standard Model We investigate the discrete$\beta$function of the 2-flavor SU(3) sextet model using the gradient flow scheme. Staggered fermion investigations suggest that the system is chirally broken, contradicting earlier Schroedinger functional Wilson fermion studies that were consistent with conformality. Our results, using improved Wilson fermions and the gradient flow RG scheme, suggests a step scaling ... More Presented by Dr. Anna HASENFRATZ on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Hadron Spectroscopy and Interactions We investigate the use of stochastically estimated light quark propagators in correlation functions involving a static color source. To this end we compute the static-light meson correlation function in the stochastic LapH framework, using N_f= 2+1 gauge configurations generated through the CLS effort. Together with the static potential, we obtain an estimate for the expected string breaking dista ... More Presented by Vanessa KOCH on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Nonzero Temperature and Density We study the$N_f=2+1$QCD at nonzero temperatures using nonperbatively improved Wilson quarks of the physical masses by the fixed scale approach. We perform physical point simulations at finite temperatures with the coupling parameters which were adopted by the PACS-CS collaboration in their studies using the reweighting technique. Zero temperature values are obtained on the PACS-CS configuration ... More Presented by Dr. Takashi UMEDA on 15/07/2015 at 09:30 Type: Poster Session: Poster Session Track: Hadron Spectroscopy and Interactions We present updated results of the heavy-meson spectrum obtained using the Oktay--Kronfeld (OK) action on MILC asqtad lattices. The OK action was designed to improve the heavy-quark action of the Fermilab formulation by including complete dimension six and part of dimension seven bilinear improvement terms. Improvement terms are truncated by power counting of order$\Lambda^3/m^3\$ for heavy-light s ... More
Presented by Mr. Yong-Chull JANG on 15/07/2015 at 09:30
Type: Poster Session: Poster Session
Track: Chiral Symmetry
We calculate the strange quark condensate and the light quark condensate by using improved staggered fermions and overlap fermions, respectively. Then we report the mass dependence of the quark condensate. We use N_f = 2+1+1 MILC HISQ(highly improved staggered quark) gauge ensembles. We use a normal CG inverter to calculate the quark condensates for higher quark masses, and the Lanczos and the eig ... More
Presented by Mr. Hwancheol JEONG on 15/07/2015 at 09:30