title: Dual Superconductivity in G2 group

abstract:
  We investigate the dual superconductivity mechanism in the exceptional group
$G_2$. This is a centerless group (no 't Hooft flux vortices are allowed) and
we check for the presence of a magnetic monopole condensate in the confined
phase by measuring on the lattice a disorder parameter related to the vacuum
expectation value of an operator carrying magnetic charge. The behaviour of the
disorder parameter is consistent with the dual superconductor picture. A first
step of an analysis on the thermodynamical properties of the theory is
conducted by mean of this operator.


title: Chiral Symmetry Restoration in Anisotropic QED(3)

abstract:
  We present results from a Monte Carlo simulation of non-compact lattice QED
in 3 dimensions in which an explicit anisotropy $\kappa$ between $x$ and $y$
hopping terms has been introduced into the action. Using a parameter set
corresponding to broken chiral symmetry in the isotropic limit $\kappa=1$, we
study the chiral condensate on $16^3$, $20^3$, and $24^3$ lattices as $\kappa$
is varied, and fit the data to an equation of state which incorporates
anisotropic volume corrections. The value $\kappa_c$ at which chiral symmetry
ispparently restored is strongly volume-dependent, suggesting that the
transition may be a crossover rather than a true phase transition. In addition
we present results on $16^3$ lattices for the scalar meson propagator, and for
the Landau gauge-fixed fermion propagator. The scalar mass approaches the pion
mass at large $\kappa$, consistent with chiral symmetry restoration, but the
fermion remains massive at all values of $\kappa$ studied, suggesting that
strong infra-red fluctuations persist into the chirally symmetric regime.
Implications for models of high-$T_c$ superconductivity based on anisotropic
QED$_3$ are discussed.


title: Algorithms for dynamical overlap fermions

abstract:
  An overview of the current status of algorithmic approaches to dynamical
overlap fermions is given. In particular the issue of changing the topological
sector is discussed.


title: Lattice Field Theory Methods in Modern Biophysics

abstract:
  An effective field theory exists describing a very large class of
biophysically interesting Coulomb gas systems: the lowest order (mean-field)
version of this theory takes the form of a generalized Poisson-Boltzmann
theory. Interaction terms depend on details (finite-size effects, multipole
properties, etc). Convergence of the loop expansion holds only if mutual
interactions of mobile charges are small compared to their interaction with the
fixed-charge environment, which is frequently not the case. Problems with the
strongly- coupled effective theory can be circumvented with an alternative
local lattice formulation, with real positive action. In realistic situations,
with variable dielectric, a determinant of the Poisson operator must be
inserted to generate correct electrostatics. Methods adopted from unquenched
lattice QCD do this very efficiently.


title: m_b and f_Bs from a combination of HQET and QCD

abstract:
  We compute the mass of the b-quark and the B_s meson decay constant in
quenched lattice QCD using a combination of HQET and the standard relativistic
QCD Lagrangian. We start from a small volume, where one can directly deal with
the b-quark, and compute the evolution to a big volume, where the finite size
effects are negligible through step scaling functions which give the change of
the observables when L is changed to 2L. In all steps we extrapolate to the
continuum limit, separately in HQET and in QCD for masses below m_b. The point
m_b is then reached by an interpolation of the continuum results. With r_0=0.5
fm and the experimental B_s and K masses we find f_Bs=191(6) MeV and the
renormalization group invariant mass M_b=6.89(11) GeV, translating into
m_b(m_b)=4.42(7) GeV in the MS-bar scheme.


title: Mass Splitting of Staggered Fermion and $SO(2D)$ Clifford Algebra

abstract:
  We present a new method to introduce rotationally invariant terms in
staggered fermions which is based on an $SO(2D)$ Clifford algebra formulation,
where $D$ means the number of space-time dimensions. We have four candidates
for improved mass terms that can split the degenerate mass of staggered
fermions. Among them, we analyze three types of combinations and find only one
case that can identify with the light single Dirac mode.


title:
Mixed Action Simulations on Staggered Background; Interpretation and
  Result for the 2-flavor QCD Chiral Condensate

abstract:
  Growing evidence indicates that in the continuum limit the rooted staggered
action is in the correct QCD universality class, the non-local terms arising
from taste breaking can be viewed as lattice artifacts. In this paper we
consider the 2-flavor Asqtad staggered action at a lattice spacing of
approximately 0.13 fm and probe the properties of the staggered configurations
by an overlap valence Dirac operator. By comparing the distribution of the
overlap eigenmodes to continuum QCD predictions we investigate if/when the
lattice artifacts are small as a function of the staggered quark mass. We
define a matching overlap quark mass where the lattice corrections are minimal
for the topological susceptibility and from the eigenmode distribution we
predict the 2-flavor chiral condensate. Our results indicate that the staggered
configurations are consistent with 2-flavor continuum QCD up to small lattice
artifacts, and predict a consistent value for the infinite volume chiral
condensate.


title:
The QCD transition temperature: results with physical masses in the
  continuum limit

abstract:
  The transition temperature ($T_c$) of QCD is determined by Symanzik improved
gauge and stout-link improved staggered fermionic lattice simulations. We use
physical masses both for the light quarks ($m_{ud}$) and for the strange quark
($m_s$). Four sets of lattice spacings ($N_t$=4,6,8 and 10) were used to carry
out a continuum extrapolation. It turned out that only $N_t$=6,8 and 10 can be
used for a controlled extrapolation, $N_t$=4 is out of the scaling region.
Since the QCD transition is a non-singular cross-over there is no unique $T_c$.
Thus, different observables lead to different numerical $T_c$ values even in
the continuum and thermodynamic limit. The peak of the renormalized chiral
susceptibility predicts $T_c$=151(3)(3) MeV, wheres $T_c$-s based on the
strange quark number susceptibility and Polyakov loops result in 24(4) MeV and
25(4) MeV larger values, respectively. Another consequence of the cross-over is
the non-vanishing width of the peaks even in the thermodynamic limit, which we
also determine. These numbers are attempted to be the full result for the
$T$$\neq$0 transition, though other lattice fermion formulations (e.g. Wilson)
are needed to cross-check them.


title:
Exploring the infrared Landau gauge propagators using large asymmetric
  lattices

abstract:
  We report on the infrared limit of the quenched lattice Landau gauge gluon
and ghost propagators computed from large asymmetric lattices. In particular,
the compatibility of the pure power law infrared solutions of the
Dyson-Schwinger equations with the lattice data is investigated and the
exponent $\kappa$ is measured. The gluon lattice data favour $\kappa \sim
0.52$, which would imply a vanishing zero momentum gluon propagator. For the
subset of lattices where the ghost propagator was computed, the data is not
compatible with a pure power law. Our data also show a decreasing running
coupling in the infrared region. Furthermore, positivity violation for the
gluon propagator is also verified.


title:
The chiral condensate on 2-flavor staggered configurations from an
  overlap operator

abstract:
  We measure the low lying eigenmodes of an overlap Dirac operator on 2--flavor
staggered configurations. By comparing the eigenmode distribution to the
predictions of Random Matrix Theory we test to what accuracy staggered
configurations describe continuum QCD. The agreement between the numerical data
and RMT implies that at our quark mass values the lattice artifacts of the
staggered configurations are comparable to overlap configurations. We identify
the overlap valence mass that best matches the staggered sea quarks and predict
the value of the infinite volume 2-flavor chiral condensate.


title: Toward Group Theory Operators for tmLQCD Hadrons

abstract:
  Extraction of the mass spectrum from twisted mass lattice QCD is facilitated
by respecting the octahedral group of rotations and accommodating the broken
parity and flavor symmetries of the theory. In this work, group theory meson
operators adapted to these constraints are constructed for the special case of
quark and antiquark fields at a common lattice site, connected by extended
gauge field paths.


title: Light baryon spectrum using improved interpolating operators

abstract:
  Energies for excited light baryons are computed in quenched QCD with a pion
mass of 490 MeV. Operators used in the simulations include local operators and
the simplest nonlocal operators that have nontrivial orbital structures. All
operators are designed with the use of Clebsch-Gordan coefficients of the
octahedral group so that they transform irreducibly under the group rotations.
Matrices of correlation functions are computed for each irreducible
representation, and then the variational method is applied to separate mass
eigenstates. We obtained 17 states for isospin 1/2 and 11 states for isospin
3/2 in various spin-parity channels including $J^P=5/2^\pm$. The pattern of the
lowest-lying energies from each irrep is discussed. We use anisotropic lattices
of volume $24^3\times 64$ with temporal lattice spacing $a_t^{-1}=6.05$ GeV
with renormalized anisotropy $\xi=3.0$.


title:
Mobility edge and locality of the overlap-Dirac operator with and
  without dynamical overlap fermions

abstract:
  We perform a systematic study of low-lying eigenmodes of $H_w$ with various
gauge actions to find the optimal choice for dynamical overlap fermion
simulations, with which one may achieve lower numerical cost for HMC and better
locality property of the overlap kernel. For this purpose, our study is made
with emphasis on the distribution of low-lying eigenvalues and the mobility
edge with and without dynamical overlap fermions.


title: Towards continuum limit of screening lengths with chiral Fermions

abstract:
  We investigate mesonic screening correlators at T=2T_c using the overlap
Fermions in the quenched approximation, where T_c is the QCD phase transition
temperature. Using lattices with temporal extent up to 8, we found that both
pseudoscalar and vector correlators exhibit a nice $cosh$ behaviour, leading to
a plateau behaviour in the local screening masses as a function of distance.
The rho and pi masses so determined show very little variation with the lattice
spacing a. This augurs well for the use of chiral Fermions, and further
suggests the small deviations of these masses from the ideal gas values are
genuine effects of interactions.


title:
Equation of state for two-flavor QCD with an improved Wilson quark
  action at non-zero chemical potential

abstract:
  The QCD thermodynamics on the lattice provides fundamental theoretical
grounds to analyze the various experimental data in relativistic heavy ion
collisions. So far, most of the numerical simulations on the lattice have been
performed by using the staggered-type fermion actions. Therefore it is
important to carry out studies using different fermion formulations to test the
uncertainties of the lattice QCD results. For this purpose, we perform
systematic simulations of two-flavor QCD with an improved Wilson quark action
to investigate the equation of state. We report the current status of our
project and show the preliminary results of the Taylor expansion coefficients
of the thermodynamic grand partition function in terms of chemical potential.


title: Phase of the Fermion Determinant at Nonzero Chemical Potential

abstract:
  We show that in the microscopic domain of QCD (also known as the
$\epsilon$-domain) at nonzero chemical potential the average phase factor of
the fermion determinant is nonzero for $\mu < m_\pi/2$ and is exponentially
suppressed for larger values of the chemical potential. This follows from the
chiral Lagrangian that describes the low-energy limit of the expectation value
of the phase factor. Explicit expressions for the average phase factor are
derived using a random matrix formulation of the zero momentum limit of this
chiral Lagrangian.


title:
Renormalization constants for Lattice QCD: new results from Numerical
  Stochastic Perturbation Theory

abstract:
  By making use of Numerical Stochastic Perturbation Theory (NSPT) we can
compute renormalization constants for Lattice QCD to high orders, e.g. three or
four loops for quark bilinears. We report on the status of our computations,
which provide several results for Wilson quarks and in particular (values
and/or ratios of) Z_V, Z_A, Z_S, Z_P. Results are given for various number of
flavors (n_f = 0, 2, 3, 4). While we recall the care which is due for the
computation of quantities for which an anomalous dimension is in place, we
point out that our computational framework is well suited to a variety of other
calculations and we briefly discuss the application of NSPT to other
regularizations (in particular the Clover action).


title: Spin-dependent potentials from lattice QCD

abstract:
  The spin-dependent corrections to the static inter-quark potential are
phenomenologically relevant to describing the fine and hyperfine spin splitting
of the heavy quarkonium spectra. We investigate these corrections, which are
represented as the field strength correlators on the quark-antiquark source, in
SU(3) lattice gauge theory. We use the Polyakov loop correlation function as
the quark-antiquark source, and by employing the multi-level algorithm, we
obtain remarkably clean signals for these corrections up to intermediate
distances of around 0.6 fm. Our observation suggests several new features of
the corrections.


title:
Analysis of the finite temperature transition for 3 flavor QCD using
  p4-improved staggered fermions

abstract:
  We present a calculation of the transition temperature for 3 flavor QCD using
p4-improved staggered fermions with two different variants of fattened links.
We examine various susceptibilities at two different values for the temporal
extent - $N_t = 4$ and $N_t = 6$ - in the vicinity of the 3 flavor transition
at vanishing chemical potential. For $N_t = 4$, we study bare quark masses in
the range $m_qa = 0.005$ to $m_qa = 0.1$, and for $N_t = 6$, we use $m_qa =
0.02$ to $m_qa = 0.2$. We also calculate hadron masses and the static quark
potential at zero temperature in order to set the scale for the transition
temperature and to study quark mass and cut-off dependent scaling properties of
the transition temperature. A comparison of the R Algorithm and the RHMC
algorithm for finite-temperature simulations is also made


title: Nuclear Force from Lattice QCD

abstract:
  The first lattice QCD result on the nuclear force (the NN potential) is
presented in the quenched level. The standard Wilson gauge action and the
standard Wilson quark action are employed on the lattice of the size 16^3\times
24 with the gauge coupling beta=5.7 and the hopping parameter kappa=0.1665. To
obtain the NN potential, we adopt a method recently proposed by CP-PACS
collaboration to study the pi pi scattering phase shift. It turns out that this
method provides the NN potentials which are faithful to those obtained in the
analysis of NN scattering data. By identifying the equal-time Bethe-Salpeter
wave function with the Schroedinger wave function for the two nucleon system,
the NN potential is reconstructed so that the wave function satisfies the
time-independent Schroedinger equation. In this report, we restrict ourselves
to the J^P=0^+ and I=1 channel, which enables us to pick up unambiguously the
``central'' NN potential V_{central}(r). The resulting potential is seen to
posses a clear repulsive core of about 500 MeV at short distance (r < 0.5 fm).
Although the attraction in the intermediate and long distance regions is still
missing in the present lattice set-up, our method is appeared to be quite
promising in reconstructing the NN potential with lattice QCD.


title: Regularizing QCD with staggered fermions and the fourth root trick

abstract:
  We investigate the properties of staggered-fermion lattice QCD in which the
fourth root of the fermion determinant is taken. We show that this theory is
non-local at non-zero lattice spacing $a$, and that the non-locality is caused
by the breaking of taste symmetry at $a\ne 0$. We then present a
renormalization-group based argument that the theory restores taste symmetry in
the continuum limit. As a consequence the theory is local in that limit, and
falls into the correct universality class. Finally, we argue that the correct
effective theory for the physics of Goldstone bosons at $a\ne 0$ is given by
staggered chiral perturbation theory with the replica trick.


title: The Spectrum of tmLQCD with Quark and Link Smearing

abstract:
  The effect of using smeared sink operators on the hadron spectrum is studied
for quenched twisted mass lattice QCD with up, down, and strange quarks.
Gaussian smearing is used for quark fields, and stout link smearing for gauge
fields. Smeared correlators are found to be dominated by the ground state with
a small contribution from excited states, leading to an improved determination
of some ground state masses.


title: Quenched penguins, the Delta I=1/2 rule, and epsilon'/epsilon

abstract:
  The transformation properties of strong penguin operators under the action of
the flavor group change when they are considered as operators in (partially)
quenched QCD instead of the unquenched theory. An ambiguity arises, which is
parameterized by new low-energy constants in the effective theory describing
non-leptonic kaon decays in the (partially) quenched setting. Here we summarize
results of the analysis for the complete set of three-flavor strong penguin
operators, consisting of products of two left-handed flavor currents, or a
left- and a right-handed current. Our results imply that (partially) quenched
lattice computations of the Delta I=1/2 rule and epsilon'/epsilon are both
affected by ambiguities intrinsic to the use of the quenched approximation at
leading order in the chiral expansion. The only exception is the partially
quenched case with three light sea quarks, consistent with general
expectations. We also address the issue of quenched ambiguities in the case of
an active charm, correcting and extending that in Phys. Rev. D 74, 014509
(2006).


title: On the infrared behavior of Green's functions in Yang-Mills theory

abstract:
  Non-perturbative properties of QCD, such as color confinement, are encoded in
the infrared behavior of correlation functions, e.g. propagators and vertices.
Various analytic predictions have been suggested for these quantities in
various gauges. Here we numerically test these predictions using lattice gauge
theory. In particular, we present results for the 2- and 3-point functions for
SU(2) Landau-gauge Yang-Mills theory in three and in four dimensions. Special
attention is paid to systematic finite-volume effects. The gluon and ghost
propagators are also evaluated in the so-called interpolating gauge (between
the Landau and the Coulomb gauge), in order to study their gauge-dependence.
Finally, we consider these propagators in Landau gauge at finite temperature,
with the aim of understanding the effect of the deconfinement phase transition
on their infrared behavior. All our results are compatible with the so-called
Gribov-Zwanziger confinement scenario.


title:
Nucleon structure in the chiral regime with domain wall fermions on an
  improved staggered sea

abstract:
  Moments of unpolarized, helicity, and transversity distributions,
electromagnetic form factors, and generalized form factors of the nucleon are
presented from a preliminary analysis of lattice results using pion masses down
to 359 MeV. The twist two matrix elements are calculated using a mixed action
of domain wall valence quarks and asqtad staggered sea quarks and are
renormalized perturbatively. Several observables are extrapolated to the
physical limit using chiral perturbation theory. Results are compared with
experimental moments of quark distributions and electromagnetic form factors
and phenomenologically determined generalized form factors, and the
implications on the transverse structure and spin content of the nucleon are
discussed.


title:
Definition and parametrization of non-perturbative effects in quenched
  QCD

abstract:
  The notion of a non-perturbative effect is ambiguous if it requires the
subtraction of a perturbative part defined by a diverging series. A common
procedure consists in dropping the order of minimal contribution and the higher
orders. This allows us to isolate very accurately the one-instanton effect for
the double-well potential. For the one plaquette gauge theory, an exact
analytical expression can be written for the non-perturbative part. We report
recent attempts to extend this approach to the average plaquette of quenched
QCD. Our goal is to express the non-perturbative effects in terms of
expressions of the form beta^B exp(-A beta) calculable semi-classically. The
situation is complicated by zeroes of the partition function in the complex
$\beta$ plane (presumably near 5.75 pm i 0.2). We discuss two methods to
describe the intermediate and large order behavior of the perturbative series.
One is inspired by mean field theory (logarithmic specific heat) and reproduces
accurately the known perturbative series with only two free parameters. A
diagrammatic interpretation of this fact is still lacking. The other is based
on infra-red renormalons with a factorial growth showing up at order larger
than 20 and a possible effective theory interpretation. These extrapolations
are compatible with the non-perturbative part of the plaquette being
proportional to a^4. We propose an exponential parametrization to the
corrections to the universal part of the beta function and find results
compatible with the suggestion of a^2 corrections made by C. Allton.


title: Heavy baryon mass spectrum from lattice QCD with 2+1 flavors

abstract:
  We study the heavy baryon mass spectrum on gauge configurations that include
2+1 flavors of dynamical improved staggered quarks. A valence clover heavy
quark is combined with two improved staggered light quark propagators to form
baryons with different flavors. We are using MILC coarse gauge configurations
with a lattice spacing of about 0.12 fm. In this preliminary investigation, we
explore the chiral limit by studying two light sea quark masses, three
different strange valence quark masses, and nine different light valence quark
masses ranging from 0.1 to 0.4 times the nominal strange quark mass.


title: Quark propagators at finite temperature with the clover action

abstract:
  We study properties of the finite temperature quark propagator by using the
SU(3) quenched lattice simulation in the Landau gauge and report numerical
results of the standard Wilson quark case as well as the improved clover one.
The mass function in the deconfinement phase is different from that of the
confinement phase, especially at low momentum regions.


title: Dynamical overlap fermion at fixed topology

abstract:
  We launched a project to perform dymanical fermion simulations using the
overlap fermion formulation for sea quarks. In order to avoid the appearace of
near-zero modes of the hermitian Wilson-Dirac operator $H_W$, we introduce a
pair of extra Wilson fermions with a large negative mass term. Crossing of the
topological boundary is then strictly prohibited, and the topological charge is
conserved during simulations. It makes the simulations substantially faster
compared to the algorithms which allow the topology change. We discuss on the
finite volume effects due to the fixed global topology.


title: On the phase structure of a chiral invariant Higgs-Yukawa model

abstract:
  In the past the construction of Higgs-Yukawa models on the lattice was
blocked by the lack of a consistent definition of a chiral invariant Yukawa
coupling term. Here, we consider a chiral invariant Higgs-Yukawa model based on
the overlap operator, realized by the Neuberger-Dirac operator. As a first step
towards a numerical examination of this model we study its phase diagram by
means of an analytic 1/N-expansion, which is possible for small and for large
values of the Yukawa coupling constant. In the case of strong Yukawa couplings
the model effectively becomes an O(4)-symmetric non-linear sigma-model.


title:
Static quark free energies at finite temperature with two flavors of
  improved Wilson quarks

abstract:
  Polyakov loop correlations at finite temperature in two-flavor QCD are
studied in lattice simulations with the RG-improved gluon action and the
clover-improved Wilson quark action. From the simulations on a $16^3 \times 4$
lattice, we extract the free energies, the effective running coupling $g_{\rm
eff}(T)$ and the Debye screening mass $m_D(T)$ for various color channels of
heavy quark--quark and quark--anti-quark pairs above the critical temperature.
The free energies are well approximated by the screened Coulomb form with the
appropriate Casimir factors. The magnitude and the temperature dependence of
the Debye mass are compared to those of the next-to-leading order thermal
perturbation theory and to a phenomenological formula given in terms of $g_{\rm
eff}(T)$. Also we made a comparison between our results with the Wilson quark
and those with the staggered quark previously reported.


title: Full QCD in external chromomagnetic field

abstract:
  We investigate the deconfining phase transition in full QCD with two flavors
of staggered fermions in presence of a constant abelian chromomagnetic field.
We find that the deconfinement temperature decreases and eventually goes to
zero by increasing the strength of the chromomagnetic field. Moreover our
results suggest that the chiral transition coincides with the deconfinement
transition and therefore even the chiral critical temperature depends on the
applied chromomagnetic field. We also find that the chiral condensate increases
with the strength of the chromomagnetic field.


title:
First results with two light flavours of quarks with maximally twisted
  mass

abstract:
  We report on first results of an ongoing effort to simulate lattice QCD with
two degenerate flavours of quarks by means of the twisted mass formulation
tuned to maximal twist. By utilising recent improvements of the HMC algorithm,
pseudo-scalar masses well below 300 MeV are simulated on volumes with spatial
size larger than 2 fm at values of the lattice spacing similar or smaller than
0.1 fm. We present first evidence that scaling violations in the pseudo-scalar
decay constant are small and well compatible with O(a) improvement.
Additionally, exploratory results for the case of N_f=2+1+1 flavours are
discussed.


title: Partially quenched QCD with a chemical potential

abstract:
  Using a chiral random matrix theory we can now derive the low energy
partition functions and Dirac eigenvalue correlations of QCD with different
chemical potentials for the dynamical and valence quarks. The results can also
be extended to complex (and purely imaginary) chemical potential. We also
discuss possible applications such as fitting to low energy constants and
understanding the phase diagrams of the full and partially quenched theories.


title: The QCD equation of state with asqtad staggered fermions

abstract:
  We report on our result for the equation of state (EOS) with a Symanzik
improved gauge action and the asqtad improved staggered fermion action at
$N_t=4$ and 6. In our dynamical simulations with 2+1 flavors we use the inexact
R algorithm and here we estimate the finite step-size systematic error on the
EOS. Finally we discuss the non-zero chemical potential extension of the EOS
and give some preliminary results.


title: Electromagnetic and spin polarisabilities in lattice QCD

abstract:
  We discuss the extraction of the electromagnetic and spin polarisabilities of
nucleons from lattice QCD. We show that the external field method can be used
to measure all the electromagnetic and spin polarisabilities including those of
charged particles. We then turn to the extrapolations required to connect such
calculations to experiment in the context of chiral perturbation theory,
finding a strong dependence on the lattice volume and quark masses.


title:
QCD thermodynamics with $N_f=2+1$ near the continuum limit at realistic
  quark masses

abstract:
  We report on our study of QCD thermodynamics with 2+1 flavors of dynamical
quarks. In this proceeding we present several thermodynamic quantities and our
recent calculation of the critical temperature. In order to investigate the
thermodynamic properties of QCD near the continuum limit we adopt improved
staggered (p4) quarks coupled with tree-level Symanzik improved glue on $N_t=4$
and 6 lattices. The simulations are performed with a physical value of the
strange quark mass and light quark masses which are in the range of
$m_q/m_s=0.05-0.4$. The lightest quark mass corresponds to a pion mass of about
150 MeV.


title: $\rho$ meson decay from the lattice

abstract:
  We present preliminary results on the $\rho$ meson decay width estimated from
the scattering phase shift of the I=1 two-pion system. The phase shift is
calculated by the finite size formula for non-zero total momentum frame (the
moving frame) derived by Rummukainen and Gottlieb, using the $N_f=2$ improved
Wilson fermion action at $m_\pi/m_\rho=0.41$ and $L=2.53 {\rm fm}$.


title: An estimate of the eta and eta-prime meson masses in Nf=2+1 lattice QCD

abstract:
  Masses of the eta and eta-prime mesons are estimated in Nf=2+1 lattice QCD
with the non-perturbatively O(a) improved Wilson quark action and the Iwasaki
RG-improved gluon action, using CP-PACS/JLQCD configurations on a 16^3 x 32
lattice at beta=1.83 (lattice spacing is 0.122 fm). We apply a stochastic noise
estimator technique combined with smearing method to evaluate correlators among
flavor SU(2) singlet pseudoscalar operators and strange pseudoscalar operators
for 10 combinations of up/down and strange quark masses. The correlator matrix
is then diagonalized to identify signals for mass eigenstates. Masses of the
ground state and the first excited state extrapolated to the physical point are
m_eta= 0.545(16) GeV and m_eta-prime= 0.871(46) GeV, being close to the
experimental values of the eta and eta-prime masses.


title: Calculation of Neutron EDM in quenched and full QCD

abstract:
  We report on a direct lattice calculation of the neutron EDM(NEDM) using the
external electric field method in both quenched and full QCD. In quenched QCD,
we use a $24^3\times 32$ lattice at $\beta=2.6$ with the Iwasaki gauge action
and the clover fermion action to examine the viability of this method. In
particular we investigate possible effects of violation of the periodic
boundary condition of the external electric field on the NEDM signal. We also
study the quark mass dependence of NEDM in quenched QCD, and observe that NEDM
seems to remain non-zero toward the chiral limit because of the quenched
artifact. In 2-flavor full QCD we employ configurations generated by the
CP-PACS collaboration on a $24^3\times 48$ lattice at $\beta=2.1$ with the same
gluon and quark actions as in the quenched case. Since the number of
configurations is limited, we employ 8 different source points per one
configuration and take an average over them. Our preliminary result at three
quark masses ($m_{PS}/m_V\simeq 0.81, 0.76, 0.69$) indicates that non-zero
value for NEDM can be obtained in full QCD. Statistical errors, however, are
still too large to show the theoretically expected behaviour for NEDM in full
QCD that it vanishes in the chiral limit.


title:
Gluon mass generation and infrared Abelian dominance in Yang-Mills
  theory

abstract:
  The dual superconductivity is believed to be a promising mechanism for quark
confinement. Indeed, what this picture is true has been confirmed in the
maximal Abelian (MA) gauge. However, it is not yet confirmed in any other gauge
and the MA gauge explicitly breaks color symmetry. To remedy this defect, we
propose to use our compact formulation of a non-linear change of variables on a
lattice. This formulation has succeeded to extract the magnetic monopole with
integer-valued magnetic charge in the gauge-invariant way. In this talk, we
present measurements of various correlation functions for the operators
constructed from the CFN variables in SU(2) Yang-Mills theory. Some of our
results reproduce previous results obtained in MA gauge, e.g.,
DeGrant-Toussaint monopole, infrared Abelian dominance and off-diagonal gluon
mass generation. These studies preserve color symmetry, in sharp contrast to
the conventional MA gauge. We argue the gauge fixing independence of these
results and the implications to quark confinement


title: Dynamical overlap fermions in the epsilon-regime

abstract:
  We report on the two-flavor QCD simulation in the epsilon-regime using the
overlap fermion formulation. Sea quark mass is reduced to ~ 2 MeV on a 16^3x32
lattice with the lattice spacing ~ 0.11fm. Topological charge is fixed at Q=0.
We compare the eigenvalue distribution of the overlap-Dirac operator with the
prediction of the chiral random matrix theory. Preliminary results on meson
correlators are also reported.


title:
The First Moment of the Kaon Distribution Amplitude from N_f=2+1 Domain
  Wall Fermions

abstract:
  We present a lattice computation of the first moment of the kaon's
leading-twist distribution amplitude. We use ensembles with 2+1 dynamical
flavours of domain wall fermions and the Iwasaki gauge action from the RBC and
UKQCD joint dataset. We observe the expected chiral behaviour and obtain
<\xi>(2GeV)=3/5a_K^1(2GeV)=0.032(3), which agrees very well with other results
obtained using QCD sum-rules and the recent lattice result from the UKQCD/QCDSF
collaboration.


title: Improvement of algorithms for dynamical overlap fermions

abstract:
  We investigate the algorithms for dynamical overlap fermions aiming at
improving the performance for large-scale simulations. We look for the best
combination of Hybrid Monte Carlo options and iterative quark solvers with
respect to the numerical costs. Our main target is a $N_f=2$ simulation with
overlap fermion on a $16^3\times 32$ lattice at lattice spacing around 0.12 fm.


title: A Strategy to Study Confinement in QCD

abstract:
  The order and the universality class of the deconfining phase transition can
provide insight into the mechanism of color confinement, in particular for
N_f=2. The mechanism of confinement by monopole condensation is reviewed.


title:
Nucleon structure in lattice QCD with dynamical domain-wall fermions
  quarks

abstract:
  We report RBC and RBC/UKQCD lattice QCD numerical calculations of nucleon
electroweak matrix elements with dynamical domain-wall fermions (DWF) quarks.
The first, RBC, set of dynamical DWF ensembles employs two degenerate flavors
of DWF quarks and the DBW2 gauge action. Three sea quark mass values of 0.04,
0.03 and 0.02 in lattice units are used with about 200 gauge configurations
each. The lattice cutoff is about 1.7 GeV and the spatial volume is about (1.9
fm)^3. Despite the small volume, the ratio of the isovector vector and axial
charges g_A/g_V and that of structure function moments <x>_{u-d}/<x>_{Delta u -
Delta d} are in agreement with experiment, and show only very mild quark mass
dependence. The second, RBC/UK, set of ensembles employs one strange and two
degenerate (up and down) dynamical DWF quarks and Iwasaki gauge action. The
strange quark mass is set at 0.04, and three up/down mass values of 0.03, 0.02
and 0.01 in lattice units are used. The lattice cutoff is about 1.6 GeV and the
spatial volume is about (3.0 fm)^3. Even with preliminary statistics of 25-30
gauge configurations, the ratios g_A/g_V and <x>_{u-d}/<x>_{Delta u - Delta d}
are consistent with experiment and show only very mild quark mass dependence.
Another structure function moment, d_1, though yet to be renormalized, appears
small in both sets.


title: Method for simulating O(N) lattice models at finite density

abstract:
  We present a method for simulating relativistic and nonrelativistic scalar
field theories at finite density, with matter transforming in the fundamental
representation of the global symmetry group O(N). The method avoids the problem
of complex probability weights which is present in conventional path integral
Monte Carlo algorithms. To verify our approach, we simulate the free and
interacting relativistic U(1)=O(2) theory in 2+1 dimensions. We compute the
two-point correlation function and charge density as a function of chemical
potential in the free theory. At weak phi^4 coupling and zero temperature we
map the m^2-mu phase diagram and compare our numerical results with
perturbative calculations. Finally, we compute properties of theT-mu phase
diagram in the vicinity of the phase transition and at bare self-couplings
large compared to the temperature and chemical potential.


title: Quarkonium at finite temperature

abstract:
  Lattice QCD studies on charmonium at finite temperature are presented After a
discussion about problems for the Maximum Entropy Method applied to finite
temperature lattice QCD, I show several results on charmonium spectral
functions. The ``wave function'' of charmonium is also discussed to study the
spatial correlation between quark and anti-quark in deconfinement phase.


title: Taste breaking effects in scalar meson correlators

abstract:
  As a consistency check of the staggered-fermion fourth-root approximation, we
analyze the a_0 and f_0 correlators, including the effects of two-meson
taste-multiplet intermediate states. Rooted staggered chiral perturbation
theory describes the contributions from the pseudoscalar taste multiplets in
terms of only a few low energy constants, which have all been previously
determined by the MILC collaboration. In previous work one of us (Prelovsek)
showed that the two-meson ``bubble'' contributions could explain the observed
anomalies in the lattice data for the isovector a_0 channel. In the present
work we extend this analysis to the f_0 channel. On a MILC collaboration
lattice ensemble at 0.12 fm with 2+1 flavors of Asqtad-improved staggered
fermions, we have made new measurements of correlators in both channels for a
variety of momenta. A fit to these correlators gives low energy constants that
are reasonably consistent with previous determinations by the MILC
collaboration.}


title: Quark confinement and gauge invariant monopoles in SU(2) YM

abstract:
  We give a short review of recently obtained results on a new lattice
formulation of the non-linear change of variables which was once called the
Cho--Faddeev--Niemi decomposition in SU(2) Yang-Mills theory.
  Based on this formulation, we proposed a new gauge-invariant definition of
the magnetic monopole current which guarantees the magnetic charge
quantization. We also demonstrated the magnetic monopole dominance in the
string tension in SU(2) Yang-Mills theory on a lattice. Our formulation enables
one to reproduce in the gauge-invariant way remarkable results obtained so far
only in the Maximally Abelian gauge.


title: Overlap Fermion in External Gravity

abstract:
  On a lattice, we construct an overlap Dirac operator which describes the
propagation of a Dirac fermion in external gravity. The local Lorentz symmetry
is manifestly realized as a lattice gauge symmetry, while the general
coordinate invariance is expected to be restored only in the continuum limit.
The lattice index density in the presence of a gravitational field is
calculated.


title: About Orientifold Planar Equivalence on the Lattice

abstract:
  The orientifold planar equivalence is the equivalence in the large-N limit of
the bosonic sectors of the super Yang-Mills and the QCD with a quark in the
antisymmetric representation. I give a sketch of the proof of the orientifold
planar equivalence in the strong-coupling and large-mass phase on the lattice.
It is still matter of discussion, if its validity extends also in the continuum
limit.


title: String tensions of SU(N) gauge theories in 2+1 dimensions

abstract:
  We calculate the energy spectrum of closed strings in SU(N) gauge theories
with N=2,3,4,6,8 in 2+1 dimensions to a high accuracy. We attempt to control
all systematic errors, and this allows us to perform a precise comparison with
different theoretical predictions.
  When we study the dependence of the string mass on its length L we find that
the Nambu-Goto prediction is a very good approximation down to relatively short
lengths, where the Luscher term alone is insufficient. We then isolate the
corrections to the Luscher term, and compare them to recent theoretical
predictions, which indeed seem to be mildly preferred by the data.
  When we take these corrections into account and extract string tensions from
the string masses, we find that their continuum limit is lower by 2%-1% from
the predictions of Karabli, Kim, and Nair. The discrepancy decreases with N,
but when we extrapolate our results to N=oo we still find a discrepancy of
0.88% which is a 4.5 sigma effect.


title: JLQCD's dynamical overlap project

abstract:
  We present an overview of our project of large-scale simulations with
dynamical overlap fermions. The first production run in two-flavor QCD is
on-going using the Iwasaki gauge action on a 16^3 \times 32 lattice at the
lattice spacing of 0.12fm with six sea quark masses down to m_{s,phys}/6, where
m_{s,phys} is the physical strange quark mass. We briefly introduce our choice
of the lattice action and simulation algorithm, and describe the present status
of the production run. Preliminary results on the light meson masses and the
static quark potential are also reported.


title:
An application of the UV-filtering preconditioner to the Polynomial
  Hybrid Monte Carlo algorithm

abstract:
  We apply the UV-filtering preconditioner, previously used to improve the
Multi-Boson algorithm, to the Polynomial Hybrid Monte Carlo (UV-PHMC)
algorithm. The performance test for the algorithm is given for the plaquette
gauge action and the $O(a)$-improved Wilson action at $\beta=5.2,
c_{\mathrm{sw}}=2.02, M_{\pi}/M_{\rho}\sim 0.8$ and 0.7 on a $16^3\times 48$
lattice. We find that the UV-filtering reduces the magnitude of the molecular
dynamics force from the pseudo fermion by a factor 3 by tuning the UV-filter
parameter. Combining with the multi-time scale molecular dynamics integrator we
achieve a factor 2 improvement.


title:
Finite temperature phase transition of two-flavor QCD with an improved
  Wilson quark action

abstract:
  We study the phase structure of QCD at finite temperatures with two flavors
of dynamical quarks on a lattice with the size $N_s^3 \times N_t=16^3 \times
4$, using a renormalization group improved gauge action and a clover improved
Wilson quark action. The simulations are made along the lines of constant
physics determined in terms of $m_{\rm PS}/m_{\rm V}$ at zero-temperature. We
show preliminary results for the spatial string tension in the high temperature
phase.


title: Hadron form factors using density-density correlators

abstract:
  Gauge invariant density-density correlators yield detailed information on
hadron structure. Hadron deformation and form factors can be extracted for
momentum transfers up to about 6 GeV$^2$. We use stochastic techniques and
dilution to compute the all to all propagator required for the exact evaluation
of density-density correlators. We present first results for the pion form
factor.


title:
Low energy scattering parameters from the solutions of the
  non-relativistic Yukawa model on a 3-dimensional lattice

abstract:
  The numerical solutions of the non-relativistic Yukawa model on a
3-dimensional size lattice with periodic boundary conditions are obtained. The
possibility to extract the corresponding -- infinite space -- low energy
parameters and bound state binding energies from eigensates computed at finite
lattice size is discussed.


title: Singlet Free Energies and Renormalized Polyakov Loop in full QCD

abstract:
  We calculate the free energy of a static quark anti-quark pair and the
renormalized Polyakov loop in 2+1- and 3- flavor QCD using $16^3 \times 4$ and
$16^3 \times 6$ lattices and improved staggered p4 action. We also compare the
renormalized Polyakov loop with the results of our earlier studies.


title: Exploring Residual Gauge Symmetry Breaking

abstract:
  Simulations of pure-gauge SU(2) lattice gauge theory are performed in the
minimal Coulomb gauge. This leaves a residual or remnant gauge symmetry still
active which is global in three directions but still local in one. Using
averaged fourth-dimension pointing links as a spin-like order parameter, the
remnant symmetry appears to undergo spontaneous symmetry breaking at around
$\beta = 2.6$. Both the Binder cumulant and the magnetization itself exhibit
crossings in this region using lattices up to $20^4$, and a susceptibility peak
is also observed. Finite size scaling indicates a weak first-order transition.
The symmetry breaking is also observed to take place in the fundamental-adjoint
plane, and is coincident with the strong first-order transition that exists
there at large $\beta_{\rm{adjoint}}$. This provides confirmation that this
phase transition is a symmetry-breaking transition. A well-known theorem
concerning the instantaneous Coulomb potential has previously proven that a
transition where such a Coulomb-gauge remnant symmetry breaks is necessarily
deconfining.


title: Generalized Potts-Models and their Relevance for Gauge Theories

abstract:
  We study the Polyakov loop dynamics originating from finite-temperature
Yang-Mills theory. The effective actions contain center-symmetric terms
involving powers of the Polyakov loop, each with its own coupling. For a
subclass with two couplings we perform a detailed analysis of the statistical
mechanics involved. To this end we employ a modified mean field approximation
and Monte Carlo simulations based on a novel cluster algorithm. We find
excellent agreement of both approaches. The phase diagram exhibits both first
and second order transitions between symmetric, ferromagnetic and
antiferromagnetic phases with phase boundaries merging at three tricritical
points. The critical exponents $\nu$ and $\gamma$ at the continuous transition
between symmetric and antiferromagnetic phases are the same as for the 3-state
spin Potts model.


title: Pseudoscalar flavor-singlets and staggered fermions

abstract:
  The Asqtad improved staggered fermion formalism has been a valuable tool in
successfully calculating the non-singlet parts of the hadronic spectrum. We are
engaged in a project to calculate the spectrum of the pseudoscalar singlet
mesons with 2+1-flavor Asqtad staggered gauge configurations. Propagators of
flavor-singlet states incorporate contributions from both disconnected and
connected diagrams, and hence are sensitive to any differences in the actions
governing the sea and valence fermions on the lattice. As such, they also
present the possibility of a probe of the validity of the ``fourth-root trick''
in the staggered fermion formulation. We present an update on our progress
toward measuring the $\eta'$ mass on 2+1-flavor Asqtad staggered gauge
configurations, including a review of methods and preliminary results. We also
show a strong correlation between ${\rm Tr}(\gamma_5\otimes 1)$ and the
topological charge in these configurations, as predicted by the index theorem.


title:
Double Hairpin Diagrams and the Planar Equivalence of N=1 Supersymmetric
  Yang-Mills Theory and One-Flavor QCD

abstract:
  Recent work by Armoni, Shifman, and Veneziano suggests a large-N equivalence
between supersymmetric Yang-Mills Theory and one-flavor QCD. One consequence of
this "orientifold projection" is that scalar and pseudoscalar mesons in
one-flavor QCD should have degenerate mass since they lie within the same
Wess-Zumino supermultiplet. We use lattice calculations to investigate the mass
shifts caused by "double-hairpin" annihilation diagrams in quenched QCD to test
for this degeneracy. Similar quark-antiquark annihilation processes are studied
in the 2-dimensional CP(N-1) model with quenched fermions.


title: Color superconductivity in ultra-dense quark matter

abstract:
  At ultra-high density, matter is expected to form a degenerate Fermi gas of
quarks in which there is a condensate of Cooper pairs of quarks near the Fermi
surface. This phenomenon is called color superconductivity. In these
proceedings I review the underlying physics of color superconductivity and our
current understanding of the possible phases of real-world quark matter. Then I
consider how lattice gauge theorists would proceed to investigate the phase
structure of dense quark matter if it were possible to perform the path
integral numerically, i.e. if the sign problem had been solved.


title:
Accelerating Staggered Fermion Dynamics with the Rational Hybrid Monte
  Carlo (RHMC) Algorithm

abstract:
  Improved staggered fermion formulations are a popular choice for lattice QCD
calculations. Historically, the algorithm used for such calculations has been
the inexact R algorithm, which has systematic errors that only vanish as the
square of the integration step-size. We describe how the exact Rational Hybrid
Monte Carlo (RHMC) algorithm may be used in this context, and show that for
parameters corresponding to current state-of-the-art computations it leads to a
factor of approximately seven decrease in cost as well as having no step-size
errors.


title: The Rational Hybrid Monte Carlo Algorithm

abstract:
  The past few years have seen considerable progress in algorithmic development
for the generation of gauge fields including the effects of dynamical fermions.
The Rational Hybrid Monte Carlo (RHMC) algorithm, where Hybrid Monte Carlo is
performed using a rational approximation in place the usual inverse quark
matrix kernel is one of these developments. This algorithm has been found to be
extremely beneficial in many areas of lattice QCD (chiral fermions, finite
temperature, Wilson fermions etc.). We review the algorithm and some of these
benefits, and we compare against other recent algorithm developements. We
conclude with an update of the Berlin wall plot comparing costs of all popular
fermion formulations.


title: D-branes, Wilson Bags, and Coherent Topological Charge Structure in QCD

abstract:
  Monte Carlo studies of pure glue SU(3) gauge theory using the overlap-based
topological charge operator have revealed a laminar structure in the QCD vacuum
consisting of extended, thin, coherent, locally 3-dimensional sheets of
topological charge embedded in 4D space, with opposite sign sheets interleaved.
Studies of localization properties of Dirac eigenmodes have also shown evidence
for the delocalization of low-lying modes on effectively 3-dimensional
surfaces. In this talk, I review some theoretical ideas which suggest the
possibility of 3-dimensionally coherent topological charge structure in
4-dimensional gauge theory and provide a possible interpretation of the
observed structure. I begin with Luscher's ``Wilson bag'' integral over the
3-index Chern-Simons tensor. The analogy with a Wilson loop as a charged world
line in 2-dimensional $CP^{N-1}$ sigma models suggests that the Wilson bag
surface represents the world volume of a physical membrane. The large-N chiral
Lagrangian arguments of Witten also indicate the existence of multiple
``k-vacuum'' states with discontinuous transitions between k-vacua at $\theta=$
odd multiples of $\pi$. The domain walls between these vacua have the
properties of a Wilson bag surface. Finally, I review the AdS/CFT duality view
of $\theta$ dependence in QCD. The dual realtionship between topological charge
in gauge theory and Ramond-Ramond charge in type IIA string theory suggests
that the coherent topological charge sheets observed on the lattice are the
holographic image of wrapped D6 branes.


title:
2+1 flavor light hadron spectrum and quark masses with the O(a) improved
  Wilson-clover quark formalism

abstract:
  We present a summary of results of the joint CP-PACS and JLQCD project toward
a 2+1 flavor full QCD simulation with the O(a)-improved Wilson quark formalism
and the Iwasaki gauge action. Configurations were generated during 2002-2005 at
three lattice spacings, a~0.076, 0.100 and 0.122 fm, keeping the physical
volume constant at (2.0fm)^3. Up and down quark masses are taken in the range
m_{PS}/m_V~0.6-0.78. We have completed the analysis for the light meson
spectrum and quark masses in the continuum limit using the full configuration
set. The predicted meson masses reproduce experimental values in the continuum
limit at a 1% level. The average up and down, and strange quark masses turn out
to be m_{ud}^{\bar{MS}}(\mu=2 GeV)=3.50(14)({}^{+26}_{-15}) MeV and
m_s^{\bar{MS}}(\mu=2 GeV)=91.8(3.9)({}^{+6.8}_{-4.1}) MeV. We discuss our
future strategy toward definitive results on hadron spectroscopy with the
Wilson-clover formalism.


title:
Calculation of $\Delta I = 3/2$ kaon weak matrix elements including
  two-pion interaction effects in finite volume

abstract:
  We calculate $\Delta I = 3/2$ kaon decay matrix elements using domain wall
fermions and the DBW2 gauge action at one coarse lattice spacing corresponding
to $a^{-1} = 1.3$ GeV. We employ the Lellouch and L\"uscher formula and its
extention for non-zero total momentum to extract the infinite volume,
center-of-mass frame decay amplitudes. The decay amplitudes obtained from the
methods correspond to those from the indirect method with full order chiral
perturbation theory. We confirm that the result is consistent with the previous
result calculated with H-parity (anti-periodic) boundary condition by
investigating the relative momentum dependence. We evaluate the decay amplitude
Re$A_2$ at the physical point by a chiral extrapolation with a polynomial
function of $m_\pi^2$ and the relative momentum as well as the Delta I = 3/2
electroweak penguin contributions to $\epsilon^\prime / \epsilon$. We found
that the result of Re$A_2$ reasonably agrees with the experiment.


title: Chiral extrapolations in 2+1 flavor domain wall fermion simulations

abstract:
  Simulations with 2+1 flavors of domain wall fermions provide us with the
opportunity to compare the lattice data directly to the predictions of
continuum chiral perturbation theory, up to corrections from the residual
chiral symmetry breaking, $m_{res}$, and $O(a)$ lattice artefacts, which are
relatively small for domain wall fermions. We present preliminary results for
the pseudoscalar meson masses and decay constants from partially quenched
simulations and examine the next-to-leading order chiral extrapolations at
small quark masses. The simulations were carried out on two lattice volumes :
$16^3\times 32$ and $24^3\times 64$, with the lattice spacing fixed at about
0.1 fm. The subtleties of the chiral fits are discussed. We also explore the
roles of $m_{res}$ and $O(a)$ terms in the NLO chiral expansions and their
effects on the chiral extrapolations for the pseudoscalar masses and decay
constants.


title:
Lattice study of the infrared behavior of QCD Green's functions in
  Landau gauge

abstract:
  We summarize the current status of our numerical results for the gluon and
ghost propagators and for the Kugo-Ojima confinement parameter in quenched
SU(3) lattice Landau gauge theory. The data for the propagators are compared to
our results obtained in the case of full QCD, simulated using two flavors of
dynamical clover-improved Wilson fermions. We demonstrate that the infrared
behavior of the ghost propagator is consistent with the Kugo-Ojima confinement
criterion. Explicit violation of reflection positivity by the gluon propagator
is shown. Additionally, we present results of a running coupling constant both
at low and at large momenta.


title: QCDLAB: Designing Lattice QCD Algorithms with MATLAB

abstract:
  This paper introduces QCDLAB, a design and research tool for lattice QCD
algorithms. The tool, a collection of MATLAB functions, is based on a
``small-code'' and a ``minutes-run-time'' algorithmic design philosophy. The
present version uses the Schwinger model on the lattice, a great
simplification, which shares many features and algorithms with lattice QCD. A
typical computing project using QCDLAB is characterised by short codes, short
run times, and the ability to make substantial changes in a few seconds. QCDLAB
1.0 can be downloaded from the QCDLAB project homepage {\tt
http://phys.fshn.edu.al/qcdlab.html}.


title: Distribution Amplitudes of Pseudoscalar Mesons

abstract:
  We present results for the first two moments of the distribution amplitudes
of pseudoscalar mesons. Using two flavors of non-perturbatively improved clover
fermions and non-perturbative renormalization of the matrix elements we perform
both chiral and continuum extrapolations and compare with recent results from
models and experiments.


title: Pion spectrum using improved staggered fermions

abstract:
  We present results for the pion multiplet spectrum calculated using both
unimproved staggered fermions and improved HYP-smeared staggered fermions. In
the case of unimproved staggered fermions, we observe (consistent with previous
work) that ${\cal O}(a^2)$ taste symmetry breaking effects are large and
comparable to the $\approx {\cal O}(p^2)$ contributions to their masses. Higher
order ${\cal O}(a^2 p^2)$ effects are also substantial enough to be seen. For
HYP-smeared staggered fermions, we find that taste breaking is much reduced.
The ${\cal O}(a^2)$ effects are observable, but are noticeably smaller than
those obtained with AsqTad-improved staggered fermions, and much smaller than
those obtained using unimproved staggered fermions, while ${\cal O}(a^2 p^2)$
effects are suppressed to such a level that we cannot observe them given our
statistical errors. From this numerical study, we conclude that HYP staggered
fermions are significantly better that AsqTad fermions from the perspective of
taste symmetry breaking.


title: $B_K$ in unquenched QCD using improved staggered fermions

abstract:
  We present preliminary results for $B_K$ calculated using improved staggered
fermions with a mixed action (HYP-smeared staggered valence quarks and AsqTad
staggered sea quarks). We investigate the effect of non-degenerate quarks on
$B_K$ and attempt to estimate the ${\cal O}(a^2)$ effect due to non-Goldstone
pions in loops. We fit the data to continuum partially quenched chiral
perturbation theory. We find that the quality of fit for $B_K$ improves if we
include non-degenerate quark mass combinations. We also observe, however, that
the fitting curve deviates from the data points in the light quark mass region.
This may indicate the need to include taste-breaking in pion loops.


title: Progress in Kaon Physics on the Lattice

abstract:
  We review recent progress in calculating kaon spectrum, pseudoscalar meson
decay constants, $B_K$, $\epsilon'/\epsilon$, $K\to \pi\pi$ matrix elements,
kaon semileptonic form factors, and moments of kaon distribution amplitudes on
the lattice. We also address the issue of how best to improve the staggered
fermion formulation for the action and operators.


title:
QCD with light Wilson quarks on fine lattices (I): first experiences and
  physics results

abstract:
  Recent conceptual, algorithmic and technical advances allow numerical
simulations of lattice QCD with Wilson quarks to be performed at significantly
smaller quark masses than was possible before. Here we report on simulations of
two-flavour QCD at sea-quark masses from slightly above to approximately 1/4 of
the strange-quark mass, on lattices with up to 64x32^3 points and spacings from
0.05 to 0.08 fm. Physical sea-quark effects are clearly seen on these lattices,
while the lattice effects appear to be quite small, even without O(a)
improvement. A striking result is that the dependence of the pion mass on the
sea-quark mass is accurately described by leading-order chiral perturbation
theory up to meson masses of about 500 MeV.


title:
One-loop Renormalisation of Lattice QCD Operators for Non-forward Matrix
  Elements: From Clover to Overlap Fermions

abstract:
  We consider the renormalisation of composite quark-antiquark operators with
one and two lattice covariant derivatives related to the lowest moments of
generalised parton distributions (GPDs) and meson distribution amplitudes
(DAs). Their matrix elements are calculated in one-loop lattice perturbation
theory for non-zero momentum transfer. Using clover and overlap fermions we
present the resulting matrices of mixing and renormalisation factors. For
overlap fermions we explicitly check the absence of mixing with
lower-dimensional operators of different chirality in particular
representations of the hypercubic group. This feature favours the use of chiral
fermions.


title: Spectral functions at non-zero momentum in hot QCD

abstract:
  We present results for meson spectral functions at non-zero momentum at
temperatures both below and above Tc, obtained in quenched simulations for a
number of valence quark masses. For the lightest quark masses, a clear
difference between the spectral functions on cold and hot lattices is observed.


title: Static-light mesons on a dynamical anisotropic lattice

abstract:
  We present results for the spectrum of static-light mesons from Nf=2 lattice
QCD. These results were obtained using all-to-all light quark propagators on an
anisotropic lattice, yielding an improved signal resolution when compared to
more conventional lattice techniques. In particular, we consider the inversion
of orbitally-excited multiplets with respect to the `standard ordering', which
has been predicted by some quark models.


title: 2+1 Flavor Lattice QCD with Luescher's Domain-Decomposed HMC Algorithm

abstract:
  We report on a study of 2+1 flavor lattice QCD with the $O(a)$-improved
Wilson quarks on a $16^3\times 32$ lattice at the lattice spacing $1/a\approx
2$GeV employing Luescher's domain-decomposed HMC(LDDHMC) algorithm. This is
dedicated to a preliminary study for the PACS-CS project which plans to
complete the Wilson-clover $N_f=2+1$ program lowering the up-down quark masses
close to the physical values as much as possible. We focus on three issues: (i)
how light quark masses we can reach with LDDHMC, (ii) efficiency of the
algorithm compared with the conventional HMC, (iii) parameter choice for the
production runs on PACS-CS.


title: Operator product expansion on the lattice: analytic Wilson coefficients

abstract:
  We present first results for Wilson coefficients of operators up to first
order in the covariant derivatives for the case of Wilson fermions. They are
derived from the off-shell Compton scattering amplitude
$\mathcal{W}_{\mu\nu}(a,p,q)$ of massless quarks with momentum $p$. The Wilson
coefficients are classified according to the transformation of the
corresponding operators under the hypercubic group H(4). We give selected
examples for a special choice of the momentum transfer $q$. All Wilson
coefficients are given in closed analytic form and in an expansion in powers of
$a$ up to first corrections.


title: Charmonium spectral functions in N_f=2 QCD at high temperature

abstract:
  Charmonium systems in two-flavour QCD at non-zero temperature are studied at,
and above the deconfining transition. Using anisotropic lattices the MEM
approach is used to extract spectral functions for these channels. By carefully
varying some of the irrelevant parameters in the MEM procedure, we confirm that
our systematic effects are under control. The eta_c and J/psi states are found
to persist at temperatures >~ 1.3 T_c in agreement with our previous dynamical
studies.


title:
Simulating at Realistic Quark Masses: Pseudoscalar Decay Constants and
  Chiral Logarithms

abstract:
  Due to improvements in computer performance and algorithms, the rapidly
increasing cost for unquenched Wilson-type fermions with lighter quarks has
been ameliorated and new simulations are now possible. Here we present results
using two flavours of O(a)-improved Wilson fermions for meson decay constants
at pseudoscalar masses down to 320MeV. Results are at several lattice spacings
down to about 0.07fm and include a non-perturbative determination of the
renormalisation constant. This enables us to attempt contact with (partially
quenched) chiral perturbation theory.


title: So you want to be a lattice theorist?

abstract:
  For this after dinner talk I intersperse images of real lattices with a
discussion of the motivations for lattice gauge theory and some current
unresolved issues.


title:
Exploratory study of the D_s spectrum in 2+1 Domain Wall QCD with heavy
  overlap

abstract:
  We present preliminary results for the D_s meson spectroscopy study on the
2+1 flavour domain wall fermion lattice configurations, generated with the
Iwasaki gauge action at beta=2.13 by the RBC-UKQCD collaboration. The
simulations are on 16^3\times32 lattice with L_s=16. We consider the charm
quark propagating as an overlap fermion at fixed lattice spacing. The
dispersion relation and mass splittings are evaluated.


title: An Improved Action for Heavy Quarks

abstract:
  We extend the Fermilab method for heavy quarks to include all interactions of
dimension six in the action. We discuss a subtlety in the power counting, which
implies that, for heavy quarks, certain interactions of dimension seven are
commensurate with some of those of dimension six. We then present tree-level
matching conditions obtained from calculating the Compton scattering amplitude
for (lattice) QCD. When the matching conditions have been applied, the improved
action removes (tree-level) discretization errors of order $a^2\bm{p}^3/m_Q$
and $a^3\bm{p}^3$.


title: Baryon-Baryon Bound States From First Principles

abstract:
  We determine baryon-baryon bound states in 3+1 dimensional ${\rm SU}(3)$
lattice QCD with two flavors, $4\times 4$ spin matrices, and in an imaginary
time formulation. For small hopping parameter, $\kappa>0$, and large glueball
mass (strong coupling), we show the existence of three-quark isospin 1/2
particles (proton and neutron) and isospin 3/2 baryons (delta particles), with
asymptotic masses $-3\ln\kappa$ and isolated dispersion curves. We only
consider the existence of bound states of total isospin $I=0,3$. Using a ladder
approximation to a lattice Bethe-Salpeter equation, baryon-baryon bound states
are found in these two sectors, with asymptotic masses $-6\ln\kappa$ and
binding energies of order $\kappa^2$. The dominant baryon-baryon interaction is
an energy-independent spatial range-one potential with an ${\cal O}(\kappa^2)$
strength. There is also attraction arising from gauge field correlations
associated with six overlapping bonds, but it is counterbalanced by Pauli
repulsion to give a vanishing zero-range potential. The overall range-one
potential results from a quark, antiquark exchange with {\it no} meson exchange
interpretation; the repulsive or attractive nature of the interaction does
depend on the isospin and spin of the two-baryon state.


title: Simulating at Realistic Quark Masses: Light quark masses

abstract:
  We present new results for light quark masses. The calculations are performed
using two flavours of $O(a)$ improved Wilson fermions. We have reached lattice
spacings as small as $a \sim 0.07$fm and pion masses down to $m_{\pi} \sim
340$MeV in our simulations. This gives us significantly better control on the
chiral and continuum extrapolations.


title: The sign problem in the $\epsilon$-regime of QCD

abstract:
  QCD in the $\epsilon$-regime at nonzero baryon chemical potential $\mu$ is
reviewed. The focus is on aspects of the sign problem which are relevant for
lattice QCD. It is discussed how spontaneous chiral symmetry breaking and the
sign problem are related through the spectrum of the Dirac operator. The
strength of the sign problem is linked to the quark mass and the chemical
potential. Specific implications for lattice QCD are discussed.


title: Confinement from Gauge Invariance in 2+1 Dimensions

abstract:
  It is shown, in D=2+1 dimensions, that by merely imposing non-abelian gauge
invariance on the temporal gauge ground state wavefunctional of an abelian
gauge theory, a confining state is obtained.


title: Center vortex model for Sp(2) Yang-Mills theory

abstract:
  The question whether the center vortex picture of the strongly interacting
vacuum can encompass the infrared dynamics of both SU(2) as well as Sp(2)
Yang-Mills theory is addressed. These two theories contain the same center
vortex degrees of freedom, and yet exhibit deconfinement phase transitions of
different order. This is argued to be caused by the effective action governing
the vortices being different in the two cases. To buttress this argument, a
random vortex world-surface model is constructed which reproduces available
lattice data characterizing Sp(2) Yang-Mills confinement properties. A new
effective action term which can be interpreted in terms of a vortex stickiness
serves to realize a first-order deconfinement phase transition, as found in
Sp(2) Yang-Mills theory. Predictions are given for the behavior of the spatial
string tension at finite temperatures.


title:
Kaon $B$-parameters for Generic $\Delta S=2$ Four-Quark Operators in
  Quenched Domain Wall QCD

abstract:
  We present a study of $B$-parameters for generic $\Delta S=2$ four-quark
operators in domain wall QCD. Our calculation covers all the $B$-parameters
required to study the neutral kaon mixing in the standard model (SM) and beyond
it. We evaluate one-loop renormalization factors of the operators employing the
plaquette and Iwasaki gauge actions. Numerical simulations are carried out in
quenched QCD with both gauge actions on $16^3\times 32\times 16$ and
$24^3\times 32\times 16$ at the lattice spacing $1/a\approx 2$GeV. We
investigate the relative magnitudes of the non-SM $B$-parameters to the SM one,
which are compared with the previous results obtained with the overlap and the
clover quark actions.


title: Exceptional Deconfinement in G(2) Gauge Theory

abstract:
  The Z(N) center symmetry plays an important role in the deconfinement phase
transition of SU(N) Yang-Mills theory at finite temperature. The exceptional
group G(2) is the smallest simply connected gauge group with a trivial center.
Hence, there is no symmetry reason why the low- and high-temperature regimes in
G(2) Yang-Mills theory should be separated by a phase transition. Still, we
present numerical evidence for the presence of a first order deconfinement
phase transition at finite temperature. Via the Higgs mechanism, G(2) breaks to
its SU(3) subgroup when a scalar field in the fundamental {7} representation
acquires a vacuum expectation value v. Varying v we investigate how the G(2)
deconfinement transition is related to the one in SU(3) Yang-Mills theory.
Interestingly, the two transitions seem to be disconnected. We also discuss a
potential dynamical mechanism that may explain this behavior.


title:
Non-perturbative scale evolution of four-fermion operators in
  two-flavour QCD

abstract:
  We apply finite-size recursion techniques based on the Schrodinger functional
formalism to determine the renormalization group running of four-fermion
operators which appear in the Delta S=2 effective weak Hamiltonian of the
Standard Model. Our calculations are done using O(a) improved Wilson fermions
with N_f=2 dynamical flavours. Preliminary results are presented for the
four-fermion operator which determines the B_K parameter in tmQCD.


title: Quark-gluon vertex in general kinematics

abstract:
  We compute the quark-gluon vertex in quenched lattice QCD, in the Landau
gauge using an off-shell mean-field O(a)-improved fermion action. The
Dirac-vector part of the vertex is computed for arbitrary kinematics. We find a
substantial infrared enhancement of the interaction strength regardless of the
kinematics.


title:
Matrix elements and diquark correlations in quenched QCD with overlap
  fermions

abstract:
  We present results for B_K and selected matrix elements for beyond the
standard model interactions obtained in quenched QCD with overlap fermions. We
also illustrate results on baryon wave-functions and diquark correlations
within baryons in the Coulomb and Landau gauge.


title: K\to\pi l \nu form factor with N_f=2+1 dynamical domain wall fermions

abstract:
  We present the latest results from the UKQCD/RBC collaborations for the
K_{l3} form factor with 2+1 flavours of dynamical domain wall quarks.
Simulations are performed on 16^3x32x16 and 24^3x64x16 lattices with three
values of the light quark mass, allowing for an extrapolation to the chiral
limit. After interpolating to zero momentum transfer, we obtain the preliminary
result f_+^{K\pi}(0)=0.9680(16), which is in excellent agreement with an
earlier N_f=2 result.


title: Signatures of S-wave bound-state formation in finite volume

abstract:
  We discuss formation of an S-wave bound-state in finite volume on the basis
of L\"uscher's phase-shift formula.It is found that although a bound-state pole
condition is fulfilled only in the infinite volume limit, its modification by
the finite size corrections is exponentially suppressed by the spatial extent
$L$ in a finite box $L^3$. We also confirm that the appearance of the S-wave
bound state is accompanied by an abrupt sign change of the S-wave scattering
length even in finite volume through numerical simulations. This distinctive
behavior may help us to discriminate the loosely bound state from the lowest
energy level of the scattering state in finite volume simulations.


title: SU(3) breaking effects in hyperon beta decay from lattice QCD

abstract:
  We present results of an exploratory study of flavor SU(3) breaking effects
in hyperon beta decays using domain wall fermions. From phenomenological point
of view, the significance of this subject is twofold: (1) to extract the
element $V_{us}$ of the Cabibbo-Kabayashi-Maskawa mixing matrix from the
$\Delta S=1$ decay process, and (2) to provide vital information to analysis of
the strange quark fraction of the proton spin with the polarized deep inelastic
scattering data. In this study, we explore the $\Xi^0 \to \Sigma^+$ beta decay,
which is highly sensitive to the SU(3) breaking since this decay corresponds to
the direct analogue of neutron beta decay under an exchange between the down
quark and the strange quark. We expose the SU(3) breaking effect on
$g_A/g_V=g_1(0)/f_1(0)$ up to the first order in breaking. The second-class
form factors $g_2$ and $f_3$, of which non-zero values are the direct signals
of the SU(3) breaking effect, are also measured. Finally, we estimate $f_1(0)$
up to the second-order correction and then evaluate $|V_{us}|$ combined with
the KTeV experiment.


title: Quark anti-quark expectation value in finite volume

abstract:
  We have computed the quark anti-quark expectation value in finite volume at
two loop in chiral perturbation theory and compare it with a formula obtained
in analogy to the Luscher formula for pion mass in finite volume. We observe
that due to the small finite size correction at two loop it is not possible to
obtain conclusions on the accuracy of the extended Luscher formula.


title: Yukawa model on a lattice: two body states

abstract:
  We present first results of the solutions of the Yukawa model as a Quantum
Field Theory (QFT) solved non perturbatively with the help of lattice
calculations. In particular we will focus on the possibility of binding two
nucleons in the QFT, compared to the non relativistic result.


title: WChPT analysis of twisted mass lattice data

abstract:
  We perform a Wilson Chiral Perturbation Theory (WChPT) analysis of quenched
twisted mass lattice data. The data were generated by two independent groups
with three different choices for the critical mass. For one choice, the
so-called pion mass definition, one observes a strong curvature for small quark
masses in various mesonic observables (''bending phenomenon''). Performing a
combined fit to the next-to-leading (NLO) expressions, we find that WChPT
describes the data very well and the fits provide very reasonable values for
the low-energy parameters.


title: Two body scattering length of Yukawa model on a lattice

abstract:
  The extraction of scattering parameters from Euclidean simulations of a
Yukawa model in a finite volume with periodic boundary conditions is analyzed
both in non relativistic quantum mechanics and in quantum field theory.


title: The QCD vacuum probed by overlap fermions

abstract:
  We summarize different uses of the eigenmodes of the Neuberger overlap
operator for the analysis of the QCD vacuum, here applied to quenched
configurations simulated by means of the Luescher-Weisz action. We describe the
localization and chiral properties of the lowest modes. The overlap-based
topological charge density (with and without UV-filtering) is compared with the
results of UV-filtering for the field strength tensor. The latter allows to
identify domains of good (anti-)selfduality. All these techniques together lead
to a dual picture of the vacuum, unifying the infrared instanton picture with
the presence of singular defects co-existent at different scales.


title:
Analytical continuation from imaginary to real chemical potential in
  2-color QCD under scrutiny

abstract:
  The method of analytical continuation from imaginary to real chemical
potential is tested in 2-color QCD. In comparison to previous studies in the
same theory, an exact updating algorithm is used and simulations are performed
closer to the thermodynamic limit. It is shown that the method considerably
improves if suitable functions are used to interpolate data with imaginary
chemical potential.


title: Pure SU(3) lattice gauge theory using operators and states

abstract:
  We study pure SU(3) gauge theory on a large lattice, using Schrodinger's
equation. Our approximate solution uses a basis of roughly 1000 states. Gauge
invariance is recovered when the color content of the ground state is
extrapolated to zero. We are able to identify the gauge invariant excitations
that remain when the extrapolation is performed. In the weak coupling limit, we
obtain promising results when we compare the excitation energies (masses) to
known results, which we derive. We discuss the application of our
nonperturbative method to the regime where glueballs are present.


title: Lattice QCD with a twisted mass term and a strange quark

abstract:
  There are three quarks with masses at or below the characteristic scale of
QCD dynamics: up, down and strange. However, twisted mass lattice QCD relies on
quark doublets. Various options for including three quark flavors within the
twisted mass approach are explored by studying the kaon masses, both
analytically (through chiral Lagrangians) and numerically (through lattice
simulations). Advantages and disadvantages are revealed for each ``strange and
twisted'' option.


title:
Z(2)-symmetric center vortex model with a first-order deconfinement
  transition

abstract:
  A random vortex world-surface model for the infrared sector of Sp(2)
Yang-Mills theory is constructed. The Sp(2) gauge group, while allowing for the
same set of center vortex fluxes as the SU(2) gauge group, induces a
significantly different dynamics on those vortex fluxes, which manifests itself
in a first-order deconfinement phase transition. As shown by the construction
presented here, a new vortex effective action term which can be interpreted in
terms of a vortex stickiness can be used to drive the deconfinement transition
towards first-order behavior. The available data from lattice Sp(2) Yang-Mills
theory are reproduced quantitatively and, in addition, predictions for the
behavior of the spatial string tension at high temperatures are presented.


title:
Highly Improved Staggered Quarks on the Lattice, with Applications to
  Charm Physics

abstract:
  We use perturbative Symanzik improvement to create a new staggered-quark
action (HISQ) that has greatly reduced one-loop taste-exchange errors, no
tree-level order a^2 errors, and no tree-level order (am)^4 errors to leading
order in the quark's velocity v/c. We demonstrate with simulations that the
resulting action has taste-exchange interactions that are at least 3--4 times
smaller than the widely used ASQTAD action. We show how to estimate errors due
to taste exchange by comparing ASQTAD and HISQ simulations, and demonstrate
with simulations that such errors are no more than 1% when HISQ is used for
light quarks at lattice spacings of 1/10 fm or less. The suppression of (am)^4
errors also makes HISQ the most accurate discretization currently available for
simulating c quarks. We demonstrate this in a new analysis of the psi-eta_c
mass splitting using the HISQ action on lattices where a m_c=0.43 and 0.66,
with full-QCD gluon configurations (from MILC). We obtain a result of~111(5)
MeV which compares well with experiment. We discuss applications of this
formalism to D physics and present our first high-precision results for D_s
mesons.


title: Asymptotic transition from Fourier series to integrals in LGT

abstract:
  It is shown that in asymptotic transition from Fourier series to integrals an
error and ambiguity may arise. Ambiguity reduces to a possibility of addition
of some distribution to the result. Properties of such distributions are
studied and conditions are established under which ambiguity doesn't arise.
Method for correction computation is suggested and conditions for correction
turning to zero are specified.


title: Rooted staggered fermions: good, bad or ugly?

abstract:
  I give a status report on the validity of the so-called ``fourth-root
trick'', i.e. the procedure of representing the determinant for a single
fermion by the fourth root of the staggered fermion determinant. This has been
used by the MILC collaboration to create a large ensemble of lattices using
which many quantities of physical interest have been and are being calculated.
It is also used extensively in studies of QCD thermodynamics. The main question
is whether the theory so defined has the correct continuum limit. There has
been significant recent progress towards answering this question. After
recalling the issue, and putting it into a broader context of results from
statistical mechanics, I critically review the new work. I also address the
related issue of the impact of treating valence and sea quarks differently in
rooted simulations, discuss whether rooted simulations at finite temperature
and density are subject to additional concerns, and briefly update results for
quark masses using the MILC configurations. An answer to the question in the
title is proposed in the summary.


title: The isospin breaking effect on baryons with Nf=2 domain wall fermions

abstract:
  We study the isospin breaking effect on octet baryons. Using the two-flavor
dynamical domain-wall QCD configurations combined with the quenched non-compact
QED configurations, the electromagnetic mass splittings between isomultiplets
(p, n), (Sigma^+, Sigma^0, Sigma^-), (Xi^0, Xi^-) are investigated. We evaluate
the main source of statistical fluctuations in the two-point correlation
function, and find that the elimination of O(e) fluctuation (e: the QED charge)
is essential to extract the signal. Preliminary results for $m_p - m_n$ as well
as other mass splittings are presented. Possible origin of systematic
uncertainty is also discussed.


title: First results in QCD with 2+1 light flavors using the fixed-point action

abstract:
  This is a progress report on 2+1 flavor simulation with the FP action on a
lattice with spatial size L=1.2fm. Since m_{ud} is quite small in our
simulation we are in the delta regime for the two light flavors where the low
lying excitations are described by a quantum mechanical rotator. From here we
extract the low energy constant F. We also measure the AWI mass and present
results on numerical issues like low-mode averaging and autocorrelation times.


title:
Modified SO(3) Lattice Gauge Theory at non zero T with Parallel
  Tempering: Monopole and Vortex Condensation

abstract:
  The deconfinement transition is studied close to the continuum limit of SO(3)
lattice gauge theory. High barriers for tunnelling among different twist
sectors causing loss of ergodicity for local update algorithms are circumvented
by means of parallel tempering. We compute monopole and center vortex free
energies both within the confining phase and through the deconfinement
transition. We discuss in detail the general problem of defining order
parameters for adjoint actions.


title: Automatic O$(a)$ improvement for twisted-mass QCD

abstract:
  We present a condition for automatic O$(a)$ improvement in twisted mass
lattice QCD, using symmetries of the Symanzik effective theory. If the
continuum part of the Symanzik effective theory is invariant under a particular
transformation, named $T_1$ in this report, scaling violations of all
quantities invariant under $T_1$ transformation are even in the lattice spacing
$a$. On the other hand, quantities non-invariant under $T_1$ vanish in the
continuum limit with odd powers in $a$. We prove this statement even for the
massive case without using the equation of motion. We also consider a few
different criteria for the $T_1$ invariant condition in lattice theories and
discuss ambiguities of the lattice condition for O$(a)$ improvement.


title:
Analytic Estimate of the Order Parameter for Monopole Condensation in
  QCD

abstract:
  The disorder parameter $<\mu>$ for the condensation of monopoles in QCD is
estimated analytically in terms of gauge invariant field strength correlators.
The continuum limit is discussed.


title:
Analytic Estimate of the Order Parameter for Magnetic Charge
  Condensation in QCD

abstract:
  The order parameter for monopole condensation is computed in terms of gauge
invariant field strength correlators. Important properties emerge of the
correlators in the confined phase, which could not be extracted by existing
numerical determinations on the lattice.


title: Semi-analytic calculation of the monopole order parameter in QCD

abstract:
  The monopole order parameter of QCD is computed in terms of gauge invariant
field strength correlators. Both quantities are partially known from numerical
simulations on the lattice. A new insight results on the structure of the
confining vacuum.


title: On color confinement

abstract: The status of the theory of color confinemnt is discussed.


title:
Flavor Twisted Boundary Conditions, Pion Momentum, and the Pion
  Electromagnetic Form Factor

abstract:
  We investigate the utility of partially twisted boundary conditions in
lattice calculations of meson observables. For dynamical simulations, we show
that the pion dispersion relation is modified by volume effects. In the isospin
limit, we demonstrate that the pion electromagnetic form factor can be computed
on the lattice at continuous values of the momentum transfer. Furthermore, the
finite volume effects are under theoretical control for extraction of the pion
charge radius.


title: $B^0_s - \bar{B^0_s}$ Mixing Parameters from Unquenched Lattice QCD

abstract:
  We determine hadronic matrix elements relevant for the mass and width
differences, $\Delta M_s$ & $\Delta \Gamma_s$ in the $B^0_s - \bar{B^0_s}$
meson system using fully unquenched lattice QCD. We employ the MILC
collaboration gauge configurations that include $u$, $d$ and $s$ sea quarks
using the improved staggered quark (AsqTad) action and a highly improved gluon
action. We implement the valence $s$ quark also with the AsqTad action and use
Nonrelativistic QCD for the valence $b$ quark. For the nonperturbative QCD
input into the Standard Model expression for $\Delta M_s$ we find $f_{B_s}
\sqrt{\hat{B}_{B_s}} = 0.281(21)$GeV. Results for four-fermion operator matrix
elements entering Standard Model formulas for $\Delta \Gamma_s$ are also
presented.


title: Chiral extrapolation of g_A with explicit Delta(1232) degrees of freedom

abstract:
  An updated and extended analysis of the quark mass dependence of the
nucleon's axial vector coupling constant g_A is presented in comparison with
state-of-the-art lattice QCD results. Special emphasis is placed on the role of
the Delta(1232) isobar. It is pointed out that standard chiral perturbation
theory of the pion-nucleon system at order p^4 fails to provide an
interpolation between the lattice data and the physical point. In constrast, a
version of chiral effective field theory with explicit inclusion of the
Delta(1232) proves to be successful. Detailed error analysis and convergence
tests are performed. Integrating out the Delta(1232) as an explicit degree of
freedom introduces uncontrolled errors for pion masses m_pi >~ 300 MeV.


title: The static quark potential for dynamical domain wall fermion simulations

abstract:
  We present preliminary results for the static quark potential computed on
some of the DWF lattice configurations generated by the RBC-UKQCD
collaborations. Most of these results were obtained using Wilson lines joining
spatial planes fixed into the Coulomb gauge. We compare the results from this
method with the earlier ones on $16^3 \times 32$ lattices using Bresenham
spatial paths with APE smeared link variables. Some preliminary results on
$24^3 \times 64$ lattices are also presented.


title:
The N to $\Delta$ axial transition form factors in quenched and
  unquenched QCD

abstract:
  The four N to $\Delta$ axial transition form factors are evaluated using
quenched QCD, using two flavors of dynamical Wilson fermions and using domain
wall valence fermions on three-flavor MILC configurations for pion masses down
to 360 MeV. We provide a prediction for the parity violating asymmetry as a
function of $Q^2$ and examine the validity of the non-diagonal
Goldberger-Treiman relation.


title: Lambda-bar, lambda_1 and m_b in three-flavor (lattice) QCD

abstract:
  The heavy-quark expansion for inclusive semi-leptonic B decays introduces
$\bar{\Lambda}$ and $\lambda_1$, which are matrix elements in heavy-quark
effective field theory. We review how they can be obtained from an analysis of
the heavy quark mass dependence of heavy-light meson masses in lattice QCD. We
present preliminary results for the bottom quark mass, $m_b$, using
$\bar{\Lambda}$ and $\lambda_1$ for the $B_s$ meson from a 2+1 sea-flavor
unquenched calculation.


title: Twisted mass QCD for weak matrix elements

abstract:
  I report on the application of tmQCD techniques to the computation of
hadronic matrix elements of four-fermion operators. Emphasis is put on the
computation of $B_K$ in quenched QCD performed by the ALPHA Collaboration. The
extension of tmQCD strategies to the study of neutral $B$-meson mixing is
briefly discussed. Finally, some remarks are made concerning proposals to apply
tmQCD to the computation of $K\to\pi\pi$ amplitudes.


title: Charm physics with highly improved staggered quarks

abstract:
  We use a relativistic highly improved staggered quark action to discretize
charm quarks on the lattice. We calculate the masses and the dispersion
relation for heavy-heavy and heavy-light meson states, and show that for
lattice spacings below .1 fm, the discretization errors are at the few percent
level. We also discuss the prospects for accurate calculations at the few
percent level of f_D_s, f_D, and the leptonic width of the psi and phi.


title: Quark number susceptibility at high temperature

abstract:
  We use three dimensional reduced effective field theory (EQCD) and lattice
calculations to determine the quark number susceptibility of QCD at high
temperature. We find our results to agree well with known perturbative
expansion as well as with other lattice data.


title: Twisted mass QCD thermodynamics: first results on apeNEXT

abstract:
  The motivations for simulating QCD thermodynamics with Wilson fermions and a
twisted mass term are introduced. The twisted mass approach provides a natural
infrared cutoff and O(a) improvement at maximal twist, and can be extended to
finite temperature. Our strategy for exploring the QCD phase diagram at finite
temperature in this setup, while taking advantage of the results at T=0, is
explained. The first results for the order parameters and susceptibilities on a
16^3 x 8 lattice are presented. All dynamical simulations are carried out on
the apeNEXT facility in Rome.


title: Chiral forms and three-flavor operators for staggered baryons

abstract:
  In staggered QCD, many staggered baryons correspond to each physical state.
Taste violations lift the continuum degeneracies of the baryons and introduce
nonzero off-diagonal elements in the mass matrix. While presenting no problem
of principle, these splittings and mixings complicate analyses of simulation
results. However, in special cases operators with good SU(3) quantum numbers
can be used to circumvent the splittings and mixings. I review what has been
learned from staggered chiral perturbation theory, outline a program of attack
for the amenable cases, and summarize the present status of work on the
staggered chiral forms and operators with good SU(3)xGTS quantum numbers.


title: Recent progress in finite temperature lattice QCD

abstract:
  I review recent progress in the determination of the QCD phase diagram at
finite temperature, in investigations of the nature of the transition or
crossover from the hadronic phase to the quark-gluon plasma phase and in the
determination of the equation of state. This talk will focus on results at zero
chemical potential.


title: Heavy flavor physics from lattice QCD

abstract:
  I review the recent status of heavy flavor physics results from lattice QCD.
In particular, I focus on the heavy-light decay constants, the bag parameters,
the form factors, and the bottom quark mass. New progresses in theoretical
methods are also reviewed.


title: Lattice QCD at Finite Density

abstract:
  I discuss different approaches to finite density lattice QCD. In particular,
I focus on the structure of the phase diagram and discuss attempts to determine
the location of the critical end-point. Recent results on the transiton line as
function of the chemical potential ($T_c(\mu_q)$) are reviewed. Along the
transition line, hadronic fluctuations have been calculated, which can be used
to characterize properties of the Quark Gluon plasma and eventually can also
help to identify the location of the critical end-point in the QCD phase
diagram on the lattice and in heavy ion experiments. Furthermore, I comment on
the structure of the phase diagram at large $\mu_q$.


title: New baryon matter in the lattice Gross-Neveu model

abstract:
  We investigate the Gross-Neveu model on the lattice at finite temperature and
chemical potential in the limit of an infinite number of fermion flavours. We
check the universality of the continuum limit of staggered and overlap fermions
at finite temperature and chemical potential. We show that at finite density a
recently discovered phase of cold baryonic matter emerges as a baryon crystal
from a spatially inhomogeneous fermion condensate. However, we also demonstrate
that on the lattice, this new phase disappears at large coupling or in small
volumes. Furthermore, we investigate unusual finite size effects that appear at
finite chemical potential. Finally, we speculate on the implications of our
findings for QCD.


title: Nucleon Form Factors: Probing the Chiral Limit

abstract:
  The electromagnetic form factors provide important hints for the internal
structure of the nucleon and continue to be of major interest for
experimentalists. For an intermediate range of momentum transfers the form
factors can be calculated on the lattice. However, reliability of the results
is limited by systematic errors due to the required extrapolation to physical
quark masses. Chiral effective field theories predict a rather strong quark
mass dependence in a range which was yet unaccessible for lattice simulations.
We give an update on recent results from the QCDSF collaboration using gauge
configurations with Nf=2, non-perturbatively O(a)-improved Wilson fermions at
very small quark masses down to 340 MeV pion mass, where we start to probe the
relevant quark mass region.


title:
Light meson masses and non-perturbative renormalisation in 2+1 flavour
  domain wall QCD

abstract:
  We present results for the light meson masses, the bare strange quark mass
and preliminary non-perturbative renormalisation of B_K in 2+1 flavour domain
wall QCD. The ensembles used were generated with the Iwasaki gauge action and
have a volume of 16^3 x 32 with a fifth dimension size of 16 and an inverse
lattice spacing of 1.6 GeV. These ensembles have u and d masses as low as one
quarter of the strange quark mass. All data were generated jointly by the UKQCD
and RBC collaborations on QCDOC machines.


title: On the Noncommutativity Approach to Supersymmetry on the Lattice

abstract:
  The noncommutativity approach to SUSY on the lattice is shown to be
inconsistent and a similar inconsistency is displayed for the link approach.


title: Coherent lattice QCD

abstract:
  We discuss a proposal for the construction of lattice QCD with gauge action,
fermionic action, theta-term, and the operators all based on the lattice Dirac
operator D with exact chiral symmetry. The simplest regularization of this type
uses the proposition that the classical limit of scalar gauge density
associated with trace of D is (up to an additive constant) proportional to
tr(FF), while the corresponding operator is local. More general formulations
from this class are considered with the aim of exposing interrelations between
gauge and fermionic aspects of QCD which are otherwise hidden in generic
formulations. Possible utility of these formulations for exploring QCD vacuum
structure is emphasized.


title: Confinement and center vortex dynamics in different gauge groups

abstract:
  The random vortex world-surface model is extended to the gauge groups SU(4)
and Sp(2). Compared to the SU(2) and SU(3) models studied previously, which
reproduce the infrared properties of the corresponding Yang-Mills theories on
the basis of a simple vortex world-surface curvature action, new dynamical
characteristics become important. In the SU(4) case, an explicit dependence of
the vortex effective action on the configuration of the Abelian magnetic
monopoles residing on the vortices emerges; in the Sp(2) case, a new
"stickiness" contribution to the vortex action serves to drive the
deconfinement phase transition towards the correct first-order behavior.