-
Francesco Giacomo Knechtli (Bergische Universitaet Wuppertal (DE))15/08/2022, 08:45
-
Urs Wenger (Universität Bern (CH))15/08/2022, 09:00
When lattice QCD is formulated in sectors of fixed quark numbers, the canonical fermion determinants can be expressed explicitely in terms of transfer matrices defined at fixed time. This in turn provides a complete factorization of the fermion determinants in temporal direction. In this talk I describe this factorization for Wilson-type fermions and present explicit constructions of the...
Go to contribution page -
Prof. James Brannick (Penn State)15/08/2022, 09:40
By employing new extended multilevel hierarchy construction principles, AMG can be applied to many new types of problems. The extended principles include general rules for choosing relaxation, constructing the coarse-level variables, the coarse-to-fine interpolation, and coarse-level equations, and a quantitative performance predictor of the multi-level cycle convergence rate, called the mock...
Go to contribution page -
Walter Wilcox15/08/2022, 10:40
We build upon our lattice QCD POLY and HFPOLY methods by using high-degree polynomials in the context of noisy disconnected diagram evaluations. Using a new, stable form of the GMRES polynomial, we obtained a subtracted error reduction in the Wilson-Dirac scalar operator on the order of a tenth the error of the non-subtracted measurement. The associated trace of subtracted high-degree...
Go to contribution page -
Kirk Soodhalter (Trinity College Dublin)15/08/2022, 11:20
We discuss the challenges of extending convergence results of classical Krylov subspace methods to their block counterparts and propose a new approach to this analysis. Block KSMs such as block GMRES are generalizations of classical KSMs, and are meant to iteratively solve linear systems with multiple right-hand sides (a.k.a. a block right-hand side) all-at-once rather than individually....
Go to contribution page -
26. Interpolation as a means of shift selection in multilevel Monte Carlo with lattice displacementsDr Travis Whyte (College of William & Mary)15/08/2022, 15:10
The calculation of disconnected diagram contributions to physical signals is
Go to contribution page
a computationally expensive task in Lattice QCD. To extract the physical
signal, the trace of the inverse Lattice Dirac operator, a large sparse matrix,
must be stochastically estimated. Because the variance of the stochastic es-
timator is typically large, variance reduction techniques must be... -
Eike Mueller (University of Bath)15/08/2022, 16:10
Monte Carlo simulations of quantum field theories on a lattice become increasingly expensive as the continuum limit is approached since the cost per independent sample grows with a high power of the inverse lattice spacing. Simulations on fine lattices suffer from critical slowdown, the rapid growth of autocorrelations in the Markov chain with decreasing lattice spacing a. This causes a strong...
Go to contribution page -
Jakob Simeth (University of Regensburg)15/08/2022, 16:50
We summarize our results for the $\eta$ and $\eta^\prime$ masses and
their four independent decay constants at the physical point as well as
their anomalous gluonic matrix elements $a_{\eta^{(\prime)}}$.The computation employs twenty-one $N_f=2+1$ Coordinated Lattice
Go to contribution page
Simulations (CLS) ensembles with non-perturbatively improved Wilson
fermions at four different lattice spacings and... -
Anthony Kennedy16/08/2022, 08:45
I shall give a pedagogical introduction to the Hamiltonian/Hybrid Monte Carlo algorithm (HMC) on Riemannian manifolds. I will explain how Hamiltonian systems are most naturally formulated in terms of Hamiltonian vector fields $\hat X$ on symplectic manifolds: the relationship between commutators of Hamiltonian vector fields and Poisson brackets, $[\hat X,\hat Y] = \widehat{\{X,Y\}}$; why a...
Go to contribution page -
Kevin Schaefers16/08/2022, 09:40
-
Phiala Shanahan16/08/2022, 10:40
I will discuss the use of machine learning methods to accelerate algorithms for gauge field generation, in particular via flow models.
Go to contribution page -
Simone Bacchio16/08/2022, 11:20
In this presentation we will show the connection between Continuous Normalizing Flows (CNF) and Trivializing Maps by Luescher. Based on the latter, we will construct a CNF that can be trained to simulate lattice field theories. We discuss strategies to train the CNF for 2D and 4D SU(3) pure-gauge theories.
Go to contribution page -
Jacob Finkenrath16/08/2022, 14:30
Discretisation of gauge theories are an elegant and successful way to solve them via supercomputers. To obtain results at the continuum, the discretised model is simulated via Monte Carlo simulations at fixed physics at different lattice spacings and then extrapolated to the continuum. In many cases the major systematic effect of the obtained result is given by the extrapolation error. To...
Go to contribution page -
Prof. Piotr Białas (Jagiellonian University)16/08/2022, 15:10
ecently a machine learning approach to Monte-Carlo simulations called Neural Markov Chain Monte-Carlo (NMCMC) is gaining traction. In its most popular form it uses neural networks to construct normalizing flows which are then trained to approximate the desired target distribution. The training is done using some form of gradient descent so gradient estimation is necessery. In my talk I will...
Go to contribution page -
Gunnar Bali (Universität Regensburg)16/08/2022, 16:10
Some selected questions:Critical slowing down with $a\to 0$.
- Rounding issues on large volumes.
- Multiscale approaches to increase signal over noise
- Benefits of (approximate eigenvectors) and how to obtain these
- Approaches to excited state contributions: multi-state fits, GEVP, smearing.
- efficient stochastic estimation of traces, all-to-all propagators, perambulatorsThese are...
Go to contribution page -
Prof. Michele Della Morte16/08/2022, 16:30
The following questions emerged from an e-mail discussion with Gustavo Ramirez:
1) Deflation (with approximate projection) as a multigrid method seems tricky to be ported to GPU architectures in an efficient way.
2) Can one understand why ? Is that solely due to the poor scalability of the 'little Dirac operator' ?
3) Isn't that then a general problem for multigrid methods on GPU ?...
Go to contribution page -
Sara Collins17/08/2022, 09:00
Nucleon matrix elements are a major lattice QCD input to the search of new physics. Their determination can be challenging, in particular at near physical quark masses. On the one hand large Euclidean time separations are necessary to determine ground state matrix elements. On...
Go to contribution page -
Mr Juan Andres Urrea Nino (Bergische Universität Wuppertal)17/08/2022, 09:40
An improvement to the widely used distillation technique is presented in the context of meson spectroscopy. Introducing meson profiles in distillation space and optimizing them for the different operators of interest significantly increases the overlap between the created states and the energy eigenstates at no considerable extra cost. These profiles give more versatility to the smearing...
Go to contribution page -
Gunnar Bali (Universität Regensburg)17/08/2022, 10:40
A precise knowledge of nucleon axial formfactors is needed for the new generation of terrestrial neutrino experiments. This is particularly challenging due to increased contamination, in this sector, from excitations, in particular from $N\pi$ scattering states. Transitions from a $N$ to a $N\pi$, mediated by an axial current are also interesting themselves, as these can be related to neutrino...
Go to contribution page -
Giannis Koutsou17/08/2022, 11:20
We present results obtained for disconnected fermion loops contributing to nucleon observables using simulations of twisted mass lattice QCD with physical quark masses and three lattice spacings. We focus on the methods employed, including multi-grid, hierarchical probing, low-mode deflation, and the so-called one-end trick.
Go to contribution page -
Juan Andres Urrea-Nino
Choose timezone
Your profile timezone: