Jefferson Lab > Events > Lattice 2008

The XXVI International Symposium on Lattice Field Theory

Plenary Program(Sort by: Speaker • Time)


Carleton DeTar (Utah)

Monday 09:00–09:50

[pdf] Recent Progress in Lattice QCD Thermodynamics

I review recent lattice results in the study of QCD at nonzero temperature, assess our current understanding, list unresolved issues, and suggest possible directions for future progress. Topics will include an assessment of recent results from a major study carried out with the Livermore Laboratory IBM Bluegene computer, a review of the outstanding issues in the determination of the transition temperature, and an examination of recent efforts to determine plasma transport coefficients.

Shinji Ejiri (BNL)

Monday 09:50–10:30

[pdf] Recent progress in lattice QCD at finite density

I review recent progress in lattice QCD at finite density. The phase diagram of QCD and the equation of state at finite temperature and density are discussed. In particular, I focus on the critical point terminating a first order phase transition line in the high density region. The critical point is one of the most interesting features that may be discovered in heavy-ion collision experiments. I summarize the current discussion on the existence of a critical point in the QCD phase diagram and discuss some attempts to find the critical point by numerical simulations.

Shailesh Chandrasekharan (Duke)

Monday 11:00–11:30

[pdf] A New Computational Approach to Lattice Quantum Field Theories

Developments in algorithms over the past decade suggest that there is a new computational approach to a class of quantum field theories. These are based on the world line/world sheet approach and can be formulated directly in Euclidean space. We describe the approach by considering $CP^N$ models, the thirring model and U(1) lattice gauge theory as examples. The new approach is likely to be more powerful than the conventional approach in some regions of parameter space, especially in the presence of chemical potentials.

Uwe-Jens Wiese (Bern)

Monday 11:30–12:00

[pdf] Rotor Spectra, Berry Phases, and Monopole Fields: from Antiferromagnets to QCD

The order parameter of a finite system with a spontaneously broken continuous global symmetry acts as a quantum mechanical rotor. Both antiferromagnets with a spontaneously broken $SU(2)_s$ spin symmetry and massless QCD with a broken $SU(2)_L \times SU(2)_R$ chiral symmetry have rotor spectra when considered in a finite volume. When an electron or hole is doped into an antiferromagnet or when a nucleon is propagating through the QCD vacuum, a Berry phase arises from a monopole field and the angular momentum of the rotor is quantized in half-integer units. This study in the $\delta$-regime complements other investigations of finite volume effects in the one-nucleon sector of QCD in the $p$- and $\epsilon$-regimes of chiral perturbation theory. A comparison of numerical lattice QCD data with finite volume predictions of chiral perturbation theory may lead to an accurate determination of low-energy parameters including $F_\pi$ and some of the Gasser-Leutwyler coefficients.

Andre Walker-Loud (William & Mary)

Monday 12:00–12:30 PM

[pdf] New lessons from the nucleon mass, lattice QCD and heavy baryon chiral perturbation theory

I will review heavy baryon chiral perturbation theory and discuss issues of convergence for both the two and three flavor theories for the nucleons, deltas and other members of the octet and decuplet baryons. I will briefly discuss the generalizations of these theories that include the lattice spacing artifacts for various lattice actions. With these effective field theories in hand, I will then examine the recent dynamical lattice calculations of the nucleon mass from the MILC, QCDSF/UKQCD, RBC/UKQCD, ETM and LHP Collaborations. Performing the chiral extrapolations of these results, one finds remarkable agreement with the physical nucleon mass, from each lattice data set. However, a careful examination of the lattice data and the resulting extrapolation functions reveals some unexpected results, serving to highlight the significant challenges in performing chiral extrapolations of baryon quantities. I will argue that knowledge of each lattice datum of the nucleon mass is required at the 1-2% level, including systematics, in order to have confidence in the two flavor heavy baryon extrapolation, at least for present day pion masses. Time permitting, I will discuss similar issues for the other octet baryon masses.


Marc Vanderhaeghen (Mainz)

Tuesday 08:30–09:15

[ppt] Overview of nucleon structure studies

This talk gives a review of recent progress in nucleon structure studies with electromagnetic probes. Recent experimental data in elastic electron nucleon scattering both at low and large momentum transfers will be discussed. The challenges which these precision measurements of nucleon electromagnetic form factors present for our theoretical understanding of nucleon structure, and for lattice QCD calculations will be outlined. The role of two-photon exchange corrections in the extraction of elastic nucleon form factors will be highlighted. A lot of recent experimental effort has also been focused on the precision measurements of the nucleon-to-$\Delta(1232)$ transition by means of electromagnetic probes. The results of these measurements are confronted with the state-of-the-art calculations based on chiral effective-field theories (EFT), lattice QCD, and large $N_c$ relations. We will also discuss a comprehensive framework for describing the quark and gluon structure of the nucleon, based on the concept of Generalized Parton Distributions (GPDs). It will be reviewed how the GPDs describe correlations between the momentum and spatial distributions of quarks, which are revealed in exclusive processes at large momentum transfers, such as the deeply virtual Compton scattering process on the nucleon. The first dedicated experiments in this field of hard exclusive processes have been performed in the past few years which will be reviewed here, as well as the theoretical progress in particular from the perspective of lattice QCD.

James Zanotti (Edinburgh)

Tuesday 09:15–10:00

[pdf] Investigations of hadron structure on the lattice

Lattice simulations of hadronic structure are now reaching a level where they are able to not only complement, but also provide guidance to, e.g. the experimental program at Jefferson Lab. In this talk I intend to review the progress that has been made in this exciting area in the past year. Topics to be covered include form factors (including transition form factors), moments of ordinary parton and generalised parton distribution functions, and moments of distribution amplitudes. I will conclude the talk with a summary of the current status of lattice simulations of each of these topics and point out unresolved issues and directions for the future.

Silas Beane (UNH)

Tuesday 10:30–11:15

[pdf] Hadronic interactions and nuclear physics

I will give an overview of efforts in the last year to calculate interactions among hadrons using lattice QCD, including the extraction of low-energy phase shifts and many-body interactions of mesons. I will discuss the present and future relevance of lattice QCD calculations for nuclear physics.

Colin Morningstar (CMU)

Tuesday 11:15–12:00

[pdf] Exploring Excited Hadrons

Progress in extracting the spectrum of excited hadron resonances is reviewed and the key issues and challenges in such computations are outlined. The importance of multi-hadron states as simulations with lighter pion masses are done is discussed, and the need for all-to-all quark propagators is emphasized.


Karl Jansen (DESY)

Wednesday 08:30–09:30

[pdf] Status of Dynamical Fermion Simulations

I will present an overview of different formulations of lattice QCD presently used in large scale simulations. Systematic effects such as the scaling behaviour in the lattice spacing, finite volume effects and non-perturbative renormalization is discussed. The question of the applicability of chiral perturbation is addressed. In addition, an update of the Berlin wall plot is presented.

Shoji Hashimoto (KEK)

Wednesday 09:30–10:00

[pdf] Physics results from dynamical overlap fermion simulations

We report on the recent physics results from the dynamical overlap fermion simulations by the JLQCD and TWQCD collaborations. The exact chiral symmetry of the overlap fermion enables us to study wide variety of physics applications. They include, for instance, the vector and axial-vector two-point functions and the strange content of the nucleon, as well as a test of the chiral expansion using pion mass, decay constant and form factors. It can also probe the topological structure of the QCD vacuum, even though the simulation has been done at a fixed topological charge.

Emanuel Katz (Boston Un.)

Wednesday 10:30–11:20

[pdf] "Ask not what the extra dimension can do for you..." (or the successes and challenges of AdS/QCD)

Recently methods inspired by the AdS/CFT correspondence have had surprising success in addressing both qualitative and quantitative aspects of non-perturbative QCD physics. I will provide an overview of some of these results. I will also discuss the challenges facing this approach, and emphasize where input from the lattice would be helpful.

Ken-Ichi Ishikawa (Hiroshima)

Wednesday 11:20–12:00

[pdf] Recent algorithm and machine developments for lattice QCD

I review the recent algorithmic development for dynamical lattice QCD simulations. The topics will include the MD integrator, preconditioning, mixed precision calculation, deflation, programing on GPGPU, etc. I also discuss the prospect on the use of these techniques on the forthcoming petaflops machines.


Elvira Gamiz (UIUC)

Friday 08:30–09:20

[pdf] Heavy flavour phenomenology from lattice QCD

Lattice calculations of hadronic parameters relevant for heavy flavour phenomenology will be the focus of this talk. I will review new results and the current status of studies of $B$ and $D$ decay constants and semileptonic decays form factors, $B^0-\bar B^0$ mixing and determinations of the quark masses $m_c$ and $m_b$. Future prospects and improvements needed in these calculations will be also covered in this talk.

Laurent Lellouch (Marseille, CPT)

Friday 09:20–10:00

[pdf] Kaon Physics: A Lattice Perspective

A review of recent measurements of kaon physics with focus on the topics of chiral perturbation theory, systematic errors and whether there are hints of new physics in tension between measurements.

Rob Pisarski (BNL)

Friday 10:30–11:15

[pdf] Heavy Ions at RHIC: an Experimental Cornucopia

In the collisions of heavy ions at ultravelativistic energies, one hopes to probe QCD in a regime where the energy density is large, over a large region of spacetime. In this talk I give an overview of the wealth of experimental results obtained from the Relativistic Heavy Ion Collider (RHIC) at Brookhaven. There are several unambiguous signals of novel behavior, very unlike a naive extrapolation from proton-proton collisions. This includes: hydrodynamic behavior, and elliptic flow; jet suppression; conical correlations of jets; and the ridge in rapidity.

Harvey Meyer (MIT)

Friday 11:15–11:45

[pdf] Energy-momentum tensor correlators and viscosity

An accurate lattice determination of the energy-momentum tensor two-point function is now possible, at least in the pure gauge theory, due to the multi-level algorithm and greater computing power. At zero temperature, the two-point functions allow for tests of the QCD sum rules approach and confinement models. At finite temperature, the spatial correlators teach us about static correlation lengths in the plasma of gluons. The temporal correlators are related by Kubo formulas to transport properties, namely shear and bulk viscosity. The small-frequency behavior of the associated spectral functions is dictated by hydrodynamics, and that at high-frequency by perturbation theory. Shear and bulk viscosity play a central role in interpreting data from heavy ion collisions at RHIC and LHC.

Yoshinobu Kuramashi (University of Tsukuba)

Friday 11:15–12:10

[pdf] PACS-CS results for 2+1 flavor lattice QCD simulation on and off the physical point

We report on the PACS-CS project focusing on direct simulation of 2+1 flavor QCD on the physical point and chiral analysis of meson and baryon masses off the physical point using both the SU(2) and SU(3) chiral perturbation theories. Configurations are generated with the O(a)-improved Wilson quark action and the Iwasaki gauge action. The up-down quark is simulated with the DDHMC algorithm armored with several improvements and the UV-filtered PHMC algorithm is implemented for the strange quark. The SU(2) and SU(3) chiral perturbation theories are applied to the pseudoscalar meson masses and the decay constants with the up-down quark mass ranging from 3 MeV to 24 MeV and two choices of the strange quark mass around the physical value. We discuss the convergences of the SU(2) and SU(3) chiral expansions up to NLO. The fit results for the low energy constants are compared with those obtained by other groups. We also investigate the quark mass dependence of the nucleon with the use of the SU(2) heavy baryon chiral perturbation theory up to NNLO. The physical quantities directly measured on the physical point are compared with those estimated by the extrapolation method.

Tomoteru Yoshie (University of Tsukuba)

Friday 12:10–12:30 PM

[pdf] Making use of the International Lattice Data Grid

The International Lattice Data Grid (ILDG) continues stable operation for about one year and has accumulated a lot of valuable configurations. After a brief review of the status of the ILDG, I will highlight large physics projects, whose configurations are already available on the grid or will be open to the public in the near future. With such information, one can make better use of the ILDG.


Luca Silvestrini (INFN, Roma)

Saturday 08:30–09:15

[pdf] Lattice QCD and New Physics searches: present and future

I review the role of Lattice QCD in testing the Standard Model and searching for New Physics. I then discuss future prospects in the LHC/SuperB era.

George Fleming (Yale)

Saturday 09:15–10:00

[pdf] New Strong Interactions for the LHC

Dynamical electroweak symmetry breaking (DEWSB) has been a viable option for the completion of the standard model for over thirty years. Precision electroweak studies indicate that the new strong interactions that break EW symmetry cannot be a scaled-up copy of QCD. Building viable models of DEWSB is difficult without a detailed understanding such non-QCD gauge theories which still confine and break chiral symmetry. We review past difficulties of studying these theories using lattice methods and describe recent progress, focusing on the role of approximate infrared conformal symmetry.

Michael Teper (Oxford)

Saturday 10:30–11:00

[pdf] Large N

I review some of what we have learned about large N gauge theories (and QCD) from lattice calculations in recent years, and point to some open problems.

Hermann Krebs (Bonn)

Saturday 11:00–11:30

[pdf] Nuclear effective field theory on the lattice

Quantum chromodynamics (QCD) describes the interaction between quarks and gluons which is responsible for the strong nuclear force. Recent advances in QCD using computational lattice methods have made it possible to accurately predict the spectrum and properties of many isolated hadrons. Unfortunately, lattice QCD calculations of many-body systems of nuclear and neutron matter or even few-body systems beyond two nucleons are presently not possible. The most significant challenge in such simulations would be to overcome the exponentially small signal-to-noise ratio caused by sign and complex phase oscillations for simulations at large quark number. Nuclear lattice simulations based on effective field theory provide an alternative method to describe few- and many-body systems at low energy without losing connection to QCD. The lattice effective field theory approach addresses the few- and many-body problem in nuclear physics by applying non-perturbative lattice methods to low-energy nucleons and pions. The effective Lagrangian is formulated on a spacetime lattice and the path integral is evaluated by Monte Carlo sampling. Pions and nucleons are treated as point-like particles on the lattice sites. By using hadronic degrees of freedom and concentrating on low-energy physics, it is possible to probe large volumes and greater number of nucleons than in lattice QCD. In my talk I will present our recent studies of the two nucleon system and neutron matter at subleading order. Accurate description of two-nucleon phase-shifts and ground state energy ratio of dilute neutron matter up to corrections of higher orders show that lattice effective field theory is a promising tool for quantitative studies of low-energy few- and many-body systems.