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Prof.
Herbert Neuberger
(Rutgers)
24/06/2014, 14:15
Theoretical Developments
Talk
The topic of the presentation is the two-point single-eigenvalue distribution correlation function of Polyakov loops in the confined phase of four dimensional SU(N) YM theory at large N.
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Liam Keegan
(CERN)
24/06/2014, 14:35
Theoretical Developments
Talk
We measure the running of the twisted gradient flow coupling in the Twisted Eguchi-Kawai (TEK) model, the SU(N) gauge theory on a single site lattice with twisted boundary conditions in the large N limit.
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Prof.
Antonio Gonzalez-Arroyo
(Instituto de Fisica Teorica UAM/CSIC)
24/06/2014, 14:55
Theoretical Developments
Talk
We present the results of our direct precision test of volume
independence for SU(N) Yang-Mills theory on the lattice with
Wilson action. Wilson loop expectation values at large N are
obtained by extrapolation and its finite volume dependence
examined for different boundary conditions.
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Dr
Hana Saito
(DESY Zeuthen)
24/06/2014, 15:15
Theoretical Developments
Talk
Tensor network methods form a family of efficient techniques of approximating quantum states. Their successes in quantum many-body physics have inspired their use for lattice gauge theories. We employed one of the tensor network techniques, called Matrix Product States, to investigate the Schwinger model in the Hamiltonian formulation. In this talk, we show our results for the temperature...
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Dr
Yuya Shimizu
(RIKEN)
24/06/2014, 15:35
Theoretical Developments
Talk
The tensor renormalization group is one of the successful methods to tackle systems whose action is complex, though the practical calculations in higher dimensions is beyond the reach of current computer facilities. The Grassmann tensor renormalization group is a generalization to systems including fermions. As a pilot study toward lattice QCD, we apply it to two-dimensional lattice QED and...
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Dr
Martin Schaden
(Rutgers University)
24/06/2014, 16:30
Theoretical Developments
Talk
I discuss the discretization of causal space-times on a topological lattice of events with hypercubic coordination whose links are light-like. Conditions that ensure this lattice is the discretization of a causal manifold are derived. They are encoded by a local topological lattice theory which has a particularly simple and appealing form when null-coframes are represented by spinors.
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Prof.
Ulli Wolff
(Humboldt University, Berlin)
24/06/2014, 16:50
Theoretical Developments
Talk
We define a finite size renormalization scheme for
$\phi^4$ theory which in the thermodynamic limit
reduces to the standard scheme used in the
broken phase. We use it to re-investigate
the question of triviality for the four dimensional
infinite bare coupling (Ising) limit. The relevant
observables all rely on two-point functions and
are very suitable for a precise estimation
with the...
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Zhaofeng Liu
(Institute of High Energy Physics)
24/06/2014, 17:10
Theoretical Developments
Talk
Two point functions of diquarks are calculated in the Landau gauge on the lattice with overlap fermions on 2+1-flavor domain wall fermion configurations. Masses of diquarks with spin 0 and 1 in the color anti-triplet representation are extracted. Pion mass dependence of the mass difference between the bad and good diquarks are studied.
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Dr
Bastian Brandt
(University of Regensburg)
24/06/2014, 17:30
Theoretical Developments
Talk
We investigate an alternative lattice discretization of continuum SU(Nc) Yang-Mills theory in which the self-interactions of the gauge field are induced by a path integral over Nc auxiliary bosonic fields which are coupled linearly to the gauge field. In two dimensions there exists an analytic proof that the new discretization reproduces Yang-Mills theory in its non-perturbative continuum...
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Mr
Boye Buyens
(University Ghent), Dr
Karel Van Acoleyen
(Ghent University)
24/06/2014, 17:50
Theoretical Developments
Talk
We consider the matrix product state formalism for the simulation of Hamiltonian lattice gauge theories. To this end, we define matrix product states which are manifestly gauge invariant. As an application, we study 1+1 dimensional one flavor quantum electrodynamics, also known as the massive Schwinger model. We are able to determine very accurately the ground state properties and one-particle...
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Dr
Indrakshi Raychowdhury
(Institute of Mathematical Sciences, Chennai, India)
25/06/2014, 09:00
Theoretical Developments
Talk
Within the Hamiltonian formulation of Lattice gauge theories, prepotentials, belonging to the fundamental representation of the gauge group and defined locally at each site of the lattice, enables us to construct local loop operators and loop states. Within this prepotential approach one gets mass gap analytically in some approximations in the weak coupling limit of the theory.
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Mr
Marcin Szyniszewski
(Lancaster University, The University of Manchester)
25/06/2014, 09:20
Theoretical Developments
Talk
We employ exact diagonalization with strong coupling expansion to the massless and massive Schwinger model. For the massless case, this allows us for a high accuracy continuum limit estimation of the ground state energy and scalar and vector mass gaps with precisions of the order of one part per billion or better.
Furthermore, we investigate the chiral condensate and compare our calculations...
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David Adams
(Nanyang Technological University)
25/06/2014, 09:40
Theoretical Developments
Talk
An update on our ongoing research on staggered Wilson fermions (a 2-flavor staggered version of Wilson fermions) will be given. Previously we found that this formulation is 4-6 times more efficient than usual Wilson fermions for inverting the Dirac matrix in quenched backgrounds of a 16^3 x 32 lattice at beta=6. Further results for 20^3 x 40 lattices will be reported which reveal that the...
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Prof.
Sinya Aoki
(Kyoto University)
25/06/2014, 10:00
Theoretical Developments
Talk
We investigate some aspects of 2-flavor QCD with $m_uยฅnot= m_d$ at low-energy, using the leading order chiral perturbation theory including anomaly effects. While nothing special happens at $m_u=0$ for the fixed $m_dยฅnot=0$, the neutral pion mass becomes zero at two critical values of $m_u$, between which the neutral pion field
condenses, leading to a spontaneously CP broken phase, the...
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Mr
Christian Zielinski
(Nanyang Technological University, Division of Mathematical Sciences)
25/06/2014, 10:20
Theoretical Developments
Talk
Results for the spectrum of the staggered Wilson Dirac operator in quenched backgrounds (beta = 5.8 and 6) are presented for a range of different lattice sizes up to 16^3 x 32. Significant improvement in the physical branch of the spectrum is observed for the larger lattices. The results are also compared with spectrum results for the usual Wilson Dirac operator in the same backgrounds.
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Dr
Richard Brower
(Boston University)
25/06/2014, 11:10
Theoretical Developments
Talk
Lattice radial quantization is a nonperturbative method especially suited to numerically solve Euclidean conformal field theories.
Tests are made for the critical surface of the
phi 4th theory at the Wilson-Fisher critical point
in 3D on R x S2 and in 2D on the Riemann sphere.
Simplicial lattice using the Finite Element Methods (FEM) or Regge calculus discretization are need to...
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Yannick Meurice
(University of Iowa)
25/06/2014, 11:30
Theoretical Developments
Talk
The idea of blocking in configuration space has played an important role in the development of the RG ideas. However, despite
being half a century old and having had a huge intellectual impact, generic numerical methods to perform blocking for lattice models have progressed more slowly than sampling methods. Blocking may be essential to deal with near conformal situations. Typically,...
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Dr
Urs Gerber
(Instituto de Ciencias Nucleares - Universidad Nacional Autonoma de Mexico)
25/06/2014, 11:50
Theoretical Developments
Talk
We consider models with topological sectors and difficulties with their Monte Carlo simulation. In particular, we are concerned with the situation where a simulation has a very long auto-correlation time with respect to the topological charge. In such cases, reliable numerical measurements are only possible within single topological sectors. The challenge is to assemble such restricted...
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Arthur Dromard
(Goethe Universitรคt, Frankfurt am Main)
25/06/2014, 12:10
Theoretical Developments
Talk
Lattice QCD simulations tend to become stuck in a single topological sector at fine lattice spacing or when using chirally symmetric overlap quarks. In such cases physical observables differ from their full QCD counterparts by finite volume corrections, which need to be understood on a quantitative level. We discuss extensions of existing relations from the literature between correlation...
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Dr
Michele Pepe
(INFN)
25/06/2014, 12:30
Theoretical Developments
Talk
We report on an ongoing project of determining non-perturbatively the finite renormalization constants of the energy-momentum tensor in the SU(3) Yang-Mills theory. We compute them by imposing on the lattice suitable Ward Identites at finite temperature and volume in presence of shifted boundary conditions. We present accurate preliminary numerical data for values of the bare coupling g_0^2...
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Hidenori Fukaya
(Osaka University)
25/06/2014, 12:50
Global topological charge tends to decorrelate very slowly or to even
freeze on fine lattice simulations, while local topological
fluctuations are expected to survive and lead to correct physical
results as long as the volume is large enough. We investigate this
issue on the recently generated configurations including dynamical
domain-wall fermions at a=0.08 fm and finer. We utilize the...
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Prof.
Apoorva Patel
(Indian Institute of Science, Bangalore, India)
26/06/2014, 14:15
Algorithms and Machines
Talk
A specific unitary evolution operator can be constructed in many
different ways, corresponding to different Hamiltonian trajectories
between the desired end-points. An optimal trajectory can then be
selected to make the evolution have the best computational complexity
and control over errors. Using Grover's quantum search algorithm as
an explicit example, it is shown that the complexity...
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Judah Unmuth-Yockey
(University of Iowa)
26/06/2014, 14:35
Algorithms and Machines
Talk
We study the two-dimensional O(3) model on the lattice using the Tensor
Renormalization Group (TRG) approach, with the goal of understanding asymptotic
scaling at both the large volume, and large beta limit. Harmonic analysis on the
Boltzmann weight introduces a sign problem into the partition function, which
makes the model difficult to study with the Worm Algorithm. The TRG...
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Dr
Agostino Patella
(CERN and Plymouth University)
26/06/2014, 14:55
Theoretical Developments
Talk
The energy-momentum tensor in lattice gauge theories requires renormalization because of the breaking of Poincare' group. The Wilson flow can be used in principle to set up non-perturbative, well-defined and, possibly, practically convenient strategies to define
a properly renormalized energy momentum tensor. I will present some preliminary data in this direction.
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Prof.
Masanori Okawa
(Hiroshima University)
26/06/2014, 15:15
Theoretical Developments
Talk
Last year, we proposed a new method to extract string tension using 4-dimensional smearing method (PL B718 (2013) 1524). In this talk we first show that results using smearing method are equivalent to those obtained by Wilson flow once the time step \epsilon is sufficiently small. We then demonstrate the practical advantage of our method by applying it to the calculation of Creutz ratio in...
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Dr
Daniel Nogradi
(Eotvos University)
26/06/2014, 15:35
Theoretical Developments
Talk
The Yang-Mills gradient flow is considered in lattice perturbation theory at leading order of the gauge coupling and O(a^8) in the lattice spacing. Improved actions are incorporated for the gauge action, the flow itself and the observable for E(t). The results lead to a setup with O(a^6) improvement at tree level.
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Stefan Sint
(Trinity College Dublin & NIC@DESY-Zeuthen)
26/06/2014, 15:55
Theoretical Developments
Talk
The gradient flow has become a very useful tool both for scale setting and for defining suitable finite volume schemes for the gauge coupling. However, surprisingly large cutoff effects have been observed in some cases. We here investigate these effects at leading order in perturbation theory and reproduce qualitative features that have previously been observed in the context of scale setting....
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Dr
Christopher Monahan
(College of William and Mary)
26/06/2014, 16:15
Theoretical Developments
Talk
We propose a new ``smeared'' operator product expansion (sOPE) in
which the set of local operators in the OPE are replaced by their locally smeared counterparts, generated by the gradient flow. The flow time, or smearing, parameter serves as a regulator for both Wilson coefficients and operator products. Matrix elements determined
nonperturbatively on the lattice using smeared degrees of...
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Ms
Yuko Murakami
(Hiroshima University)
27/06/2014, 14:15
Theoretical Developments
Talk
We investigate the universality of Mรถbius Domain Wall Fermions (MDWF) in the Schrรถdinger Functional (SF) scheme at tree level. We introduce the SF boundary condition to the MDWFs by adding a temporal boundary operator. When the fifth dimensional parameters of the MDWF are a constant, this construction seems to be natural according to the Luescherโs universality prescription for the overlap...
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Prof.
Artan Borici
(Uiversity of Tirana)
27/06/2014, 14:35
It is well known that Crank-Nicolson discretization scheme is second order accurate in time. Its application in the case of the Dirac operator leads to a lattice theory with reduced doublers and broken parity. Adding a 3-space Wilson term one obtains a single fermion which is second order accurate in time. In the case of an imaginary term the doubler degeneracy is lifted and the ground state...
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Mr
Venkitesh Ayyar
(Duke University)
27/06/2014, 14:55
Massless fermions can become massive due to interactions through the mechanism of Spontaneous Symmetry Breaking (SSB). This mode of mass generation is popular and has been used in the Standard Model. Here, we explore
the possibility of fermions acquiring a mass through interactions, but without SSB.\\
We consider a fermion system on a cubical lattice and introduce an on-site four-fermion...
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Dr
Axel Cortes Cubero
(City University of New York)
27/06/2014, 15:15
Theoretical Developments
Talk
Massive Yang-Mills theory is known to be renormalizable in 1+1 dimensions. The gluon mass is introduced by coupling the gauge field to an SU(N) principal chiral nonlinear sigma model. The proof of renormalizability relies on the asymptotic freedom of the sigma model. However, renormalization forces the gluon mass to infinity. The continuum theory is in a confined phase rather than a Higgs...
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