PETROS DIMOPOULOS
(University of Rome 'La Sapienza')
15/06/2010, 18:00
Weak decays and matrix elements
We present preliminary results on the of neutral kaon oscillations in extensions of the Standard Model. Using $N_f=2$ maximally twisted sea quarks and Osterwalder-Seiler valence quarks, we achieve both O(a)-improvement and continuum-like renormalization pattern for the relevant four-fermion operators. We perform simulations at three values of the lattice spacing and extrapolate/interpolate...
Hideo Matsufuru
(High Energy Accelerator Research Organization (KEK))
15/06/2010, 18:00
Chiral symmetry
We investigate the Nc=2 lattice gauge theories with two
flavors of the Wilson fermions (and twisted mass ghosts) in
fundamental and adjoint representations.
The phase structure of these theories is studied in the
coupling-quark mass plane by observing meson correlation
functions and spectral density of the Dirac operator.
Apostolos Skouroupathis
(University of Cyprus, Department of Physics)
15/06/2010, 18:00
Standard model parameters and renormalization
In this work we compute the one-loop 1PI 2-point perturbative bare Green's functions of:
- The fermion propagator $\bar{\Psi} \Psi$
- Local fermion bilinear operators $\bar{\Psi} \Gamma \Psi$
- Extended fermion bilinear operators $\bar{\Psi} \Gamma_{\{\mu} \overleftrightarrow{D}_{\nu\}} \Psi$
where $\Gamma$ corresponds to the Dirac operators and $\overleftrightarrow{D} = \frac{1}{2}\left(...
Massimo Di Pierro
(DePaul University)
15/06/2010, 18:00
Algorithms and machines
Vis is a system that implements Software as a Service for Lattice QCD computations. At its core it is a repository of gauge confurations with web and web services interfaces. It gives users the ability to queue tasks and execute them in background. Tasks can be FermiQCD program and/or visualization algorithms (topological charge, polyakov lines, evergy density, etc.). The web services are...
Terrence Draper
(University of Kentucky)
15/06/2010, 18:00
Chiral symmetry
We champion use of the absolute measure of local chirality since it has a uniform distribution for randomly reshuffled chiral components so that any deviations from uniformity in the associated "X-distribution" are directly attributable to QCD-induced dynamics.
We observe a transition in the qualitative behavior of the absolute X-distribution of low-lying eigenmodes which, we propose,...
marcello pivanti
(INFN and University of Ferrara)
15/06/2010, 18:00
Algorithms and machines
This poster covers in details the architecture of the application-driven
AuroraScience supercomputer. This machine is a large 3D array of latest
generation Intel processors, with nearest-neigbor processors connected by
a network with toroidal topology. Each node has a peak (double precision)
performance of 100-150 Gflops. This machine has been engineered to be
reliably assembled in...
Anthony Kennedy
(University of Edinburgh),
Bálint Joó
(JLab),
Mike Clark
(Harvard University),
Paulo Silva
(Universidade de Coimbra)
15/06/2010, 18:00
Algorithms and machines
We show how to improve the molecular dynamics step of HMC, both by tuning the integrator using Poisson brackets measurements and with the use of force gradient integrators. We show results for moderate lattice sizes.
Hinnerk Stueben
(Konrad-Zuse-Zentrum fuer Informationstechnik Berlin (ZIB))
15/06/2010, 18:00
Algorithms and machines
BQCD is a Hybrid Monte-Carlo program that simulates lattice QCD with
dynamical Wilson fermions. The development of BQCD began in Berlin in
1998 for studies of parallel tempering and the Aoki phase. For ten
years BQCD has been one of the main production programs of the QCDSF
collaboration. The program has been ported to and optimised for
different massively parallel machines, for...
Maria Paola Lombardo
(INFN)
15/06/2010, 18:00
Applications beyond QCD
We study QCD with 12 light flavors at intermediate
values of the bare lattice coupling. We contrast and compare
the results for the chiral condensate and the the pion mass
with different theoretical models motivated by the
physics of the Goldstone phase and universal properties
of chiral symmetry breaking. Our analysis favors
chiral symmetry restoration.
Yuji Sakai
(Kyushu University)
15/06/2010, 18:00
Nonzero temperature and density
Lattice QCD (LQCD) has the sign problem at real quark chemical potential. There are some regions with no sign problem; one is the imaginary quark chemical potential region and another is the real and imaginary isospin chemical potential regions.
We show that the Polyakov-loop extended Nambu--Jona-Lasinio (PNJL) model can reproduce LQCD data in the regions. We also determine the parameters...
Marina Marinkovic
(Humboldt University Berlin)
15/06/2010, 18:00
Algorithms and machines
Mass preconditioned HMC and DD-HMC are among the most popular algorithms to simulate improved Wilson fermions. We present a comparison of the performance of the two algorithms for realistic quark masses and lattice sizes.
Alessandro Papa
(Università della Calabria and INFN),
Mario Gravina
(Laboratoire de Physique Théorique, Université de Paris-Sud 1, Orsay1),
Roberto Fiore
(Università della Calabria and INFN)
15/06/2010, 18:00
Critical properties of the compact three-dimensional U(1) lattice gauge theory are explored at finite temperatures. The critical point of the deconfinement phase transition, critical indices and the string tension are studied numerically on lattices with temporal extension Nt = 8 and spatial extension ranging from L = 32 to 256. The critical indices, which govern the behaviour across the...
Gennaro Cortese
(Università della Calabria and INFN-Cosenza)
15/06/2010, 18:00
Vacuum structure and confinement
The 2D Z(5) vector model is investigated through the determination of critical points and various critical indices. To this purpose, a new cluster algorithm has been developed for 2D Z(N) models with odd values of N. Results are compared with analytical predictions.
Swagato Mukherjee
(Assistant Physicist)
15/06/2010, 18:00
Nonzero temperature and density
We discuss the universal properties of the QCD chiral transition for both zero and small but non-zero chemical potential. We outline how those universal properties can be used to extract the curvature of the line of chiral transitions in the T-\mu plane for small chemical potential. We present evidence of these universal properties and result for this curvature obtained using lattice...
Harald Markum
(Vienna University of Technology)
15/06/2010, 18:00
Theoretical developments
Theories with noncommutative space-time coordinates represent alternative candidates of grand unified theories. We discuss U(1) gauge theory in 2 and 4 dimensions on a lattice with N sites. The mapping to a U(N) plaquette model in the sense of Eguchi and Kawai can be used for computer simulations. In 2D it turns out that the formulation of the topological charge leads to the imaginary part of...
Simon Heybrock
(University of Regensburg)
15/06/2010, 18:00
Algorithms and machines
In analogy to Neubergers double pass algorithm for the Conjugate Gradient inversion with multi-shifts we introduce a double pass variant for BiCGstab(l). A possible application is the Overlap Operator of QCD at non-zero chemical potential, where the kernel of the sign function becomes non-Hermitian. The sign function can be replaced by a partial fraction expansion, requiring multi-shift...
Johannes Weber
(University of Tsukuba)
15/06/2010, 18:00
Chiral symmetry
Minimally doubled fermions reconcile standard chiral symmetry with a
minimal number of flavours in accordance with the restrictions of the
Nielsen-Ninomiya no-go theorem. Hypercubic symmetry however, is
necessarily broken by the alignment of two poles of the propagator in
momentum space.
The specified direction of the symmetry breaking strongly affects
the properties of these actions....
Taegil Bae
(Seoul National University, Seoul, Korea (Republic of))
15/06/2010, 18:00
Weak decays and matrix elements
We report our first experience with the analysis of $B_K$ calculated on the MILC ultrafine lattices using improved staggered fermions. The results are preliminary. However, since it is so close to the continuum, the prematurity does not desecrate the bright splendor of the results much.
Bicudo Pedro
(Instituto Superior Técnico, Lisboa)
15/06/2010, 18:00
Vacuum structure and confinement
The interpretation of the Landau gauge lattice gluon propagator as a massive type bosonic propagator is investigated. This is relevant for the analytical studies of the Landau gauge gluon propagator, since in Lattice QCD we are able to also compute the non-pertubative infrared gluon mass and compute how it matches with the ultraviolet region addressed in pertubative QCD.
Our analysis...
Huey-Wen Lin
(University of Washington)
15/06/2010, 18:00
Hadronic structure and interactions
We report a recent breakthrough in lattice QCD calculations of hadron
form factors at large momentum transfer. Conventional lattice
form-factor calculations typically reach about 2.5 GeV$^2$ or less,
but in this work the transfer momentum is pushed as high as 6 GeV$^2$.
Our approach can be applied to isotropic lattices and lattices with
smaller lattice spacing to calculate even...
Georg von Hippel
(Institut f. Kernphysik, Uni Mainz)
15/06/2010, 18:00
Algorithms and machines
We present an algorithm to automatically derive Feynman rules for lattice perturbation theory in background field gauge. Vertices with an arbitrary number of both background and quantum legs can be derived automatically from both gluonic and fermionic actions. The algorithm is a generalisation of our earlier algorithm based on prior work by L\"uscher and Weisz. We also present techniques...
Richard Evans
(Universitaet Regensburg)
15/06/2010, 18:00
Weak decays and matrix elements
We investigate two alternatives to the Sequential Propagator Method used in Lattice QCD calculations of heavy-light semileptonic form factors. In the first method, which we refer to as the Stochastic Propagator Method, we replace the sequential propagator with a stochastic all-to-all propagator. In the second method, we employ the so called "one-end trick". After minimizing the stochastic...
Kenichi Ishikawa
(Hiroshima University, Department of Physical Science)
15/06/2010, 18:00
Algorithms and machines
The Large Hadron Collider (LHC) experiment has begun to trap the tail of
Higgs boson and to find the evidence of a theory beyoned the standerd model (SM).
Motivated from the unnatural feature of elementary scalar Higgs field,
many models beyond the SM have been proposed and studied.
The technicolor (TC) model is one of them and describes the origin
of electroweak symmetry breaking...
John Laiho
(University of Glasgow)
15/06/2010, 18:00
Weak decays and matrix elements
We present a new method for determining K->pipi matrix elements from lattice simulations. This method is less costly than direct simulations of K->pipi at physical kinematics, and evades the Maiani-Testa no-go theorem by simulating with both pions at rest. It improves, however, upon the traditional "indirect" approach of constructing the K->pi pi matrix elements using NLO SU(3) ChPT, which...
Elisabetta Pallante
(University of Groningen)
15/06/2010, 18:00
Hadron spectroscopy
We discuss the computation of the K and D meson masses in the N_f = 2+1+1 twisted mass lattice QCD setup, where explicit heavy flavour and parity breaking occurs at finite lattice spacing. We present three methods suitable in this context, and verify their consistency.
Pedro Bicudo
(Instituto Superior Técnico, Lisboa)
15/06/2010, 18:00
Algorithms and machines
We discuss the CUDA approach to the simulation of pure gauge Lattice SU(2).
CUDA is a hardware and software architecture developed by Nvidia for
computing on the GPU.
We present an analysis and performance comparison between the GPU and
CPU with single precision.
Analysis with single and multiple GPU's, using CUDA and OPENMP, are
also presented.
In order to obtain a high performance,...
Michael Creutz
(Brookhaven Lab)
15/06/2010, 18:00
Chiral symmetry
Minimally doubled chiral fermions have the unusual property of a
single local field creating two fermionic species. Spreading the
field over nearby neighbors allows construction of combinations that
isolate specific modes. Combining these fields into bilinears
produces meson fields of specific quantum numbers.
Anne-Mari Mykkänen
(University of Helsinki and Helsinki Institute of Physics),
Jarno Rantaharju
(University of Helsinki and Helsinki Institute of Physics)
15/06/2010, 18:00
Applications beyond QCD
The research of strongly coupled beyond-the-standard-model theories has generated significant interest in non-abelian gauge field theories with different number of fermions in different representations. Motivated by technicolor scenarios, we study the non-perturbative improvement of the Wilson-clover action using SU(2) gauge fields and fermions in fundamental and adjoint representations. The...
Stephan Durr
(Wuppertal University and Julich Supercomputing Center)
15/06/2010, 18:00
Hadron spectroscopy
A status report is given for a joint project between the Budapest-Marseille-Wuppertal collaboration and the Regensburg group to study the quark mass-dependence of octet baryons in SU(3) Baryon ChPT. This formulation is expected to extend to larger masses than Heavy-Baryon ChPT. Its applicability will be tested with 2+1 flavor data which cover three lattice spacings and pion masses down to...
Jair Wuilloud
(uni Bern)
15/06/2010, 18:00
Chiral symmetry
The investigated theory has one Wilson fermion in the fundamental
representation with colour gauge group SU(3).
In addition to studying the one flavour theory particle spectrum,
we test by Monte-Carlo simulations
the existence of a CP-symmetry breaking phase
and predictions from the orientifold planar equivalence.
The poster also describes the computation of the...
Björn Wellegehausen
(TPI, University Jena)
15/06/2010, 18:00
Vacuum structure and confinement
G2 is the smallest simple and simply connected lie group with a trivial center. Therefore investigations of G2 gauge theories may help to clarify the relevance of center symmetry for confinement. Beside this it has an intriguing connection to SU(3) gauge theorie and to QCD. If one couples a scalar field in the fundamental representation to the gauge field one can break the G2 gauge symmetry to...
Massimo D'Elia
(Universita` di Genova & INFN)
15/06/2010, 18:00
Nonzero temperature and density
We consider the endpoint of the Roberge-Weiss first order transition line, which is present for imaginary values of the baryon chemical potential, and study its nature in two flavor QCD as a function of the quark masses. We present evidence that the endpoint is first order (hence a triple point) for low quark masses, discuss the fate of the further first order lines departing from it, and...
Mushtaq Loan
(International School, Jinan University)
15/06/2010, 18:00
Nonzero temperature and density
We present results of rho meson mass in lattice QCD with two degenerate flavours of dynamical quarks at finite temperature. Our preliminary results show that the ground state mass remains almost unchanged as the temperature is approaching to the critical temperature from the below. Above T_{c}, we find indication that mesonic excitations survive both at finite quark mass and in the physical limit.
Shinji Ejiri
(Niigata University)
15/06/2010, 18:00
Nonzero temperature and density
We study scaling behavior of a chiral order parameter defined by an axial Ward-Takahashi identity in two-flavor QCD. It has been shown that the scaling behavior of the chiral order parameter agrees with the scaling function of the three-dimensional O(4) spin model by a simulation with the RG (Iwasaki) improved gauge action and clover improved quark action at zero chemical potential. We extend...
Waseem Kamleh
(University of Adelaide)
15/06/2010, 18:00
Hadronic structure and interactions
The effect of a uniform background magnetic field on the wave
function of the d-quark in the ground state of the proton is
calculated in Lattice QCD. We focus on the wave functions in the
Landau and Coulomb gauges. When the quarks are annihilated at
different lattice sites, we observe the formation of a scalar u-d
diquark pair within the proton in the Landau gauge, which is not
present...
Claudio Bonati
(PI)
15/06/2010, 18:00
Algorithms and machines
We will show our implementation of the RHMC algorithm for staggered fermions on Graphics Processing Units using the NVIDIA CUDA programming language. While previous studies exclusively deal with the Dirac matrix inversion problem, our code performs the complete MD trajectory on the GPU. After pointing out the main bottlenecks and how to circumvent them, we discuss the performance of our code.
Boram Yoon
(Seoul National University)
15/06/2010, 18:00
Weak decays and matrix elements
We report a recent progress in determining $B_K$ based on the SU(2) analysis of the data. We use HYP staggered fermions as valence quarks and use asqtad staggered fermions as sea quarks. A number of systematic errors are reviewed in some details.
Jangho Kim
(Department of Physics and Astronomy, Seoul National University)
15/06/2010, 18:00
Weak decays and matrix elements
We report a recent progress in the SU(3) analysis of $B_K$ calculated using improved staggered fermions in a mixed action environment: valence quarks are HYP staggered fermions and sea quarks are asqtad staggered fermions. The systematic errors reviewed in some details.
Yong-Chull Jang
(Department of Physics and Astronomy, Seoul National University)
15/06/2010, 18:00
Standard model parameters and renormalization
We discuss about the systematic errors in $B_K$ calculated
on the MILC lattices using improved staggered fermions. We address
unresolved issues on the finite volume effect, dependence of $B_K$ on
the light sea quark masses, dependence of $B_K$ on the strange sea
quark mass, and so on.
Monahan Chris
(University of Cambridge)
15/06/2010, 18:00
Standard model parameters and renormalization
We present a calculation of the b quark mass from lattice NonRelativistic QCD (NRQCD). The b quark mass is extracted using the two-loop NRQCD heavy quark energy shift and mass renormalisation, previously calculated to only one-loop. These parameters are obtained with a hybrid technique: gluonic contributions are extrapolated from a quenched high-beta simulation and the fermionic contributions...
Anthony Francis
(Universitaet Bielefeld)
15/06/2010, 18:00
Nonzero temperature and density
We explore properties of hadronic excitations at high
temperature in the chiral limit by investigating
hadron correlation functions in the deconfined phase
of quenched QCD. This is achieved by performing a systematic analysis of
the influence of cut-off effects on light quark meson
correlators at $T=1.5 T_c$ using clover improved Wilson
fermions on quenched gauge field...
Massimo D'Elia
(Universita` di Genova & INFN)
15/06/2010, 18:00
Nonzero temperature and density
We investigate the properties of the deconfining/chiral restoring transition for two flavor QCD in presence of a uniform background magnetic field. We adopt a standard staggered discretization of the fermion action, different values of the bare quark mass corresponding to pion masses ranging from 200 to 500 MeV, and magnetic fields up to eB = 1 GeV^2. We present first results regarding the...
Michela D'Onofrio
(University of Helsinki)
15/06/2010, 18:00
Applications beyond QCD
The baryon number in the Standard Model is violated by non-perturbative sphaleron transitions. At temperatures above the electroweak scale, the rate of the sphaleron transitions is unsuppressed and has been accurately measured using effective theories on the lattice. At temperatures substantially below the electroweak scale, the Higgs field expectation value is large and the sphaleron rate is...
Claudio Bonati
(PI)
15/06/2010, 18:00
Vacuum structure and confinement
The numerical implementation of monopole creation operator was pointed out to have problems related to bulk transitions that could possibly affect the interpretation of its mean value as an order parameter for monopole condensation. Preliminary evicence is presented that these unexpected behaviours are in fact only due to lattice artefacts and do not overcome the physical intarpretation of the...
Yu Maezawa
(RIKEN)
15/06/2010, 18:00
Nonzero temperature and density
The viscous coefficients are input of the calculation of the relativistic dissipative hydrodynamics and should be given by a microscopic theory.
It is known that the coefficients will be calculated by the Green-Kubo-Nakano (GKN) formula if the fluid is described by the relativistic Navier-Stokes (RNS) equation.
However, we cannot apply the RNS theory because this theory is acausal and...
Paulo Silva
(Center for Computational Physics, University of Coimbra)
15/06/2010, 18:00
Vacuum structure and confinement
The gluon and ghost propagators are computed using both quenched
and dynamical configurations for the same lattice spacings. The Wilson
fermions are simulated at several quark masses. Furthermore, the effect of
the Gribov copies is evaluated for all sets of configurations.
Sara Collins
(University of Regensburg)
15/06/2010, 18:00
Hadronic structure and interactions
We report on an ongoing project to calculate disconnected contributions to hadronic structure with results on QCDSF dynamical $n_f=2$ configurations at three volumes.
