Spectral densities from the lattice

We discuss a method to extract the K\"all\'{e}n-Lehmann spectral density of a particle (be it elementary or bound state) propagator by means of 4d lattice data. We employ a linear regularization strategy, commonly known as the Tikhonov method with Morozov discrepancy principle. An important virtue over the popular maximum entropy method is the possibility to also probe unphysical spectral densities, as, for example, of a confined gluon. We apply our proposal to the SU(3) glue sector.Comment: 7 pages, 9 figures, talk given at the 31st International Symposium on Lattice Field Theory (LATTICE 2013), July 29-August 3 2013, Mainz, German

The lattice Landau gauge gluon propagator: lattice spacing and volume dependence

The interplay between the finite volume and finite lattice spacing is investigated using lattice QCD simulations to compute the Landau gauge gluon propagator. Comparing several ensembles with different lattice spacings and physical volumes, we conclude that the dominant effects, in the infrared region, are associated with the use of a finite lattice spacing. The simulations show that decreasing the lattice spacing, while keeping the same physical volume, leads to an enhancement of the infrared gluon propagator. In this sense, the data from $\beta=5.7$ simulations, which uses an $a \approx 0.18$ fm, provides a lower bound for the infinite volume propagator.Comment: Final version to appear in Phys Rev

Production of Anticentauro Events in Ultra-Relativistic Heavy Ion Collisions

We propose a novel method for studying the production of anticentauro events in high energy heavy ion collisions utilizing Chebyshev expansion coefficients. These coefficients have proved to be very efficient in investigating the pattern of fluctuations in neutral pion fraction. For the anticentauro like events, the magnitude of first few coefficients is strongly enhanced (~3 times) as compared to those of normal HIJING events. Various characteristics of Chebyshev coefficients are studied in detail and the probability of formation of exotic events is calculated from the simulated events.Comment: Proceedings of Poster Session, 19th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions (Quark Matter 2006), November 14-20, 2006, Shanghai, Chin

Landau Gauge Fixing on GPUs and String Tension

We explore the performance of CUDA in performing Landau gauge fixing in Lattice QCD, using the steepest descent method with Fourier acceleration. The code performance was tested in a Tesla C2070, Fermi architecture. We also present a study of the string tension at finite temperature in the confined phase. The string tension is extracted from the color averaged free energy and from the color singlet using Landau gauge fixing.Comment: 7 pages, 4 figures, 1 table. Contribution to the International Meeting "Excited QCD", Peniche, Portugal, 06 - 12 May 201

Landau gauge fixing on the lattice using GPU's

In this work, we consider the GPU implementation of the steepest descent method with Fourier acceleration for Laudau gauge fixing, using CUDA. The performance of the code in a Tesla C2070 GPU is compared with a parallel CPU implementation.Comment: 3 pages, 1 figure, Proceedings of the Xth Quark Confinement and the Hadron Spectrum, 8-12 October 2012, TUM Campus Garching, Munich, German