Chris Sachrajda
(Univ. of Southampton)
19/07/2010, 11:00
The RBC-UKQCD calculation of Re[A_2] and Im[A_2] for almost physical kaons and pions will be reviewed, where A_2 is the amplitude for the decay of a kaon into two-pions with isospin 2. The simulations are performed on a 32^3X64, L_s=32 lattice with N_f=2+1 flavours of light quarks, using the DWF-Iwasaki/DSDR action and the mass dependence of the amplitude is studied.
The calculations include...
Qiu Liu
(Columbia University)
19/07/2010, 11:30
We report a direct lattice calculation of the K-->pipi decay matrix elements for both Delta I=1/2 and 3/2 channels on 2+1 flavor, domain wall fermion, 16^3X32 lattices. This first direct calculation of the Delta I=1/2 channel is made possible by collecting very large statistics and studying the decay at pi-pi threshold with 420 MeV pions in a small, 1.8 fm box. All possible contractions are...
Simon Catterall
(Syracuse University)
20/07/2010, 11:00
I show that a particular twist of N=4 super Yang-Mills in three dimensions with gauge group SU(2) possesses a set of classical vacua corresponding to the space of flat connections of the complexified gauge group SL(2,C). The theory also containsa set of topological observables corresponding to Wilson loops wrapping non-trivial cycles of the base manifold. This moduli space
and set of...
Anna Hasenfratz
(Univ. of Colorado, Boulder)
20/07/2010, 11:30
Models with many fermions or fermions in higher representations can be candidates for extended technicolor or unparticle theories. The phenomenologically most interesting models show "walking" or develop an infrared fixed point in strong gauge coupling. Lattice methods can be used to explore the phase diagram of these models, and Monte Carlo renormalization group (MCRG) methods are especially...
Stefan Sint
(Trinity College, Dublin)
21/07/2010, 11:00
The chirally rotated Schroedinger functional provides a test bed for universality and automatic O(a) improvement. In joint work with Bjoern Leder, we have implemented the chirally rotated Schroedinger functional and carried out extensive quenched simulations. We demonstrate that, after proper tuning of a dimension 3 boundary counterterm, the expected chirally rotated boundary conditions are...
Thomas DeGrand
(Univ. of Colorado, Boulder)
21/07/2010, 11:30
I compute the difference of vector and axial vector current correlators in the weak coupling phase of (lattice-regulated) SU(3) gauge theory with two flavors of symmetric-representation dynamical fermions. For the chosen parameters of the simulation, this model exhibits walking and for all practical purposes it is conformal. Consequences for the phenomenology of beyond Standard Model
physics...
David Kaplan
(Inst. of Nuclear Theory, Seattle)
22/07/2010, 11:00
Understanding the properties of few to many strongly interacting fermions in a finite volume is of interest in many areas of physics, and is computationally challenging. One of the simplest non-trivial systems to look at are "unitary fermions": non- relativistic fermions with short range interactions and infinite scattering length. This is a conformal theory which can be studied...
Anastassios Vladikas
(Univ. of Tor Vergata, Rome)
23/07/2010, 11:00
In the framework of the Flavianet European Network, a group of lattice and ChPT theorists, known as the Flavianet Lattice Averaging Group (FLAG), is making an effort to create a compilation of results on a few physical quantities, which critically summarize the state of the art
in Pion and Kaon Physics. The quantities examined so far are quark masses, f_K/f_\pi, the Kaon decay form factor...
Stefano Capitani
(University of Mainz)
23/07/2010, 11:30
Minimally doubled fermions have been proposed as a strictly local discretization of the QCD quark action, which also preserves chiral symmetry at finite cut-off. We study the renormalization and mixing properties of two particular realizations of minimally doubled fermions in lattice perturbation theory at one loop. We also construct conserved axial-vector currents, which have a simple...
John Bulava
(DESY, Zeuthen)
26/07/2010, 11:00
I will report on recent results of the on-going efforts by the ALPHA collaboration to determine hadronic quantities in the heavy-flavor sector. In particular, I will highlight a precise calculation of the B*Bpi coupling in which a method to evaluate mesonic three-point correlation functions with small statistical and systematic errors is used. The efficacy of this approach is also compared...
Giancarlo Rossi
(Univ. of Tor Vergata, Rome)
26/07/2010, 11:30
A method to extract B-physics parameters (b-quark mass and fB, fBs decay constants) from currently available lattice data is presented. The approach is based on the idea of constructing
appropriate ratios of heavy-light meson masses and decay constants, respectively, possessing a precisely known static limit, and evaluating them at various pairs of heavy quark masses around the charm. Via...
Stephen Sharpe
(Univ. of Washington, Seattle)
27/07/2010, 11:00
I describe ongoing work to implement the idea of volume-reduction for various QCD-like lattice gauge theories. If reduction holds, then many physical, infinite-volume, quantities can be obtained, by doing calculations on lattices of any size, including a single site, and taking the large N_c limit. Reduction holds as long as certain conditions are fulfilled, the most stringent of which is that...
Norman Christ
(Columbia University)
28/07/2010, 14:00
Enhanced algorithms and multi-teraflops computer resources are making an increasing range of kaon physics accessible to lattice QCD. After an overview of the RBC/UKQCD chiral fermion simulation program, results will be presented for f_K/f_pi, B_K and the complex amplitude A_2 determining Delta I = 3/2, K -> pi+pi decay. Initial work and prospects for the similar Delta I = 1/2 K -> pi+pi...
Jacobus Verbaarschot
(State University of New York, Stony Brook)
29/07/2010, 11:00
Because of the phase of the fermion determinant lattice QCD at nonzero chemical potential cannot be simulated by standard stochastic algorithms. However, if the sign problem is not severe, various independent methods give consistent results. We will investigate the severity of the sign problem by means of chiral perturbation theory. The distribution of the average phase factor, the chiral...
Francesco Knechtli
(Bergische Universitaet Wuppertal)
29/07/2010, 11:30
We present results from a meanfield expansion around a non-trivial background in five-dimensional SU(2) gauge theory. The physics goals are the study of dimensional reduction and spontaneous symmetry breaking. On the torus the meanfield expansion shows a second order phase transition in the non-compact regime, where the anisotropy becomes a relevant parameter. Dimensional reduction and effects...
Francesco Sannino
(CP3-Origins, Odense, Denmark)
30/07/2010, 11:00
I will review the state-of-the-art of the phase diagram of chiral and non chiral gauge theories obtained using several distinct analytical methods. I will then show how to use this information to construct models of dynamical electroweak symmetry breaking. Finally I will discuss relevant applications for cosmology.
Christof Gattringer
(Univ. of Graz, Austria)
02/08/2010, 11:00
We explore the role of center symmetry and its explicit and spontaneous breaking in different parts of the QCD phase diagram. In particular the following issues are addressed: 1) In a fugacity expansion the grand canonical fermion determinant can be decomposed into canonical determinants with a fixed quark number. The canonical determinants have simple transformation properties under center...
Hartmut Wittig
(Univ. of Mainz)
02/08/2010, 11:30
I report on an on-going project based on simulations with Nf=2 flavours of O(a) improved Wilson fermions. The main focus is on precision determinations of the pion form factor using twisted boundary conditions. I also describe our efforts to control a variety of systematic uncertainty in calculations of nucleon form factors. Finally, I present some lattice results for the hadronic vacuum...
Francesco Di Renzo
(Univ. of Parma and INFN)
03/08/2010, 11:00
The author has been involved for quite a long time in a non-standard approach to Lattice Perturbation Theory (a stochastic method named NSPT).
I will try to have a look at some unconventional approaches to PT computations on which we have been trying to move some steps forward for a while, like non-trivial vacua or the Dirac spectrum.
Kim Splittorff
(Niels Bohr Inst., Copenhagen)
03/08/2010, 11:30
This talk discusses the effect of the lattice spacing on the microscopic spectrum of the Wilson Dirac operator. Exact results are obtained from Wilson chiral Perturbation Theory in sectors of
fixed topology, where topology is defined as the number of real eigenvalues of the Wilson Dirac operator. We compute the density of these real modes as well as the microscopic spectral density
of the...
Kari Rummukainen
(University of Helsinki)
04/08/2010, 14:00
In phenomeologically acceptable technicolor theories the gauge coupling evolves very slowly, "walks", over a specific range of energies. Thus, the beta-function of the theory has a near-zero at a non-zero value of the coupling constant, where the theory becomes almost conformal. Because the almost-fixed point is at relatively strong coupling, non-perturbative lattice simulations are required...
Robert Edwards
(Jefferson Lab)
05/08/2010, 11:30
There has been a resurgence of interest in spectroscopy with a new generation of experiments that are starting worldwide, for example BES III, GSI/Panda, and Jefferson Lab's GlueX project as well as CLAS12.
Spectroscopy reveals fundamental aspects of hadronic physics. However, the excited spectrum of light quark mesons and baryons is not well determined or understood. The GlueX project will...
Yoshinobu Kuramashi
(University of Tsukuba)
06/08/2010, 11:00
We present the results of the physical point simulation in 2+1 flavor lattice QCD with the nonperturbatively O(a)-improved Wilson quark action and the Iwasaki gauge action at beta=1.9 on a 32^3x64 lattice. The physical quark masses together with the lattice spacing is determined with m_pi, m_K and m_Omega as physical inputs.
There are two key algorithmic ingredients to make possible the...
Laurent Lellouch
(Centre de Physique Theorique)
06/08/2010, 11:30
I will present the recent progress made by the Budapest-Marseille-Wuppertal
collaboration in simulating N_f=2+1 QCD with pion masses down to around 120 MeV,
and will show some of the results obtained on these and earlier sets of configurations.
Sinya Aoki
(Univ. of Tsukuba)
09/08/2010, 11:00
A few years ago, we proposed a method to extract potentials from the Nambu-Bethe-Salpeter wave function and indeed obtained the nucleon-nucleon potential in lattice QCD. In this talk, as an extension of this method, we propose a new method to extract information of hadron interactions in lattice QCD above the inelastic threshold. After theoretical considerations of this method, we present...
Pierre van Baal
(Institut Lorentz for Theoretical Physics, University of Leiden)
10/08/2010, 11:00
The progress on calorons (finite temperature instantons) is sketched. In particular there is some interest for confining temperatures, where the holonomy (the asymptotic value of the Polyakov loop) is non-trivial. I also will give more recent results by others.
Akira Ukawa
(University of Tsukuba)
11/08/2010, 14:00
Lattice QCD is now turning a crucial corner. Progress over the last four decades in physics, algorithms, and supercomputers is finally bringing it to the point where it is possible to carry out calculations in a large enough box and a small enough lattice spacing at the physical masses for light quarks. Soon we shall no longer be simulating but calculating strong interactions as they take...
Anthony Kennedy
(Univ. of Edinburgh)
12/08/2010, 11:00
A new momentum space formalism is given for the renormalization of quantum field theories to all orders of perturbation theory, in which there are manifestly no overlapping divergences. We prove the BPH theorem in this formalism, and show how the required local subtractions add up to counterterms in the action. Applications include a proof of the renormalization of lattice perturbation...
Taku Izubuchi
(Brookhaven National Laboratory)
13/08/2010, 11:00
Each individual masses of up, down, and strange quarks are extracted using lattice QCD+QED simulation using Nf=2+1 DWF ensemble generated by RBC/UKQCD collaboration. An analysis on isospin breaking in Kaon mass, or proton/neutron mass difference will be also presented.
Tom Blum
(Univ. of Connecticut)
13/08/2010, 11:30
I discuss current RBC and UKQCD collaboration 2+1 flavor QCD simulations using domain wall fermions and the Iwasaki+dislocation-suppressing-determinant-ratio (I-DSDR) gauge action with beta=1.75. Unitary pion masses for these simulations are 180 MeV and 250 MeV.
Partially quenched pion masses go down to the physical pion mass. The size of the lattice is 32^3X64X32, corresponding to a volume...
