Lattice QCD Thermodynamics on the Grid

Abstract

We describe how we have used simultaneously $\mathcal{O}(10^3)$ nodes of the EGEE Grid, accumulating ca. 300 CPU-years in 2-3 months, to determine an important property of Quantum Chromodynamics. We explain how Grid resources were exploited efficiently and with ease, using user-level overlay based on Ganga and DIANE tools above standard Grid software stack. Application-specific scheduling and resource selection based on simple but powerful heuristics allowed to improve efficiency of the processing to obtain desired scientific results by a specified deadline. This is also a demonstration of combined use of supercomputers, to calculate the initial state of the QCD system, and Grids, to perform the subsequent massively distributed simulations. The QCD simulation was performed on a $16^3\times 4$ lattice. Keeping the strange quark mass at its physical value, we reduced the masses of the up and down quarks until, under an increase of temperature, the system underwent a second-order phase transition to a quark-gluon plasma. Then we measured the response of this system to an increase in the quark density. We find that the transition is smoothened rather than sharpened. If confirmed on a finer lattice, this finding makes it unlikely for ongoing experimental searches to find a QCD critical point at small chemical potential.

References in corpus (4)

• The chiral critical line of N_f=2+1 QCD at zero and non-zero baryon density
• The chiral critical point of Nf=3 QCD at finite density to the order (mu/T)^4
• Ganga: a tool for computational-task management and easy access to Grid resources
• A QCD chiral critical point at small chemical potential: is it there or not?

Cited by in corpus (9)

• The QCD phase diagram at nonzero quark density
• Lattice QCD and heavy ion collisions: a review of recent progress
• The QCD equation of state at finite density from analytical continuation
• Ganga: a tool for computational-task management and easy access to Grid resources
• Future Physics Perspectives on the Equation of State from Heavy Ion Collisions to Neutron Stars
• Quantum Simulation of Chiral Phase Transitions
• Critical versus spurious fluctuations in the search for the QCD critical point
• Strange mass dependence of the tricritical point in the U(3)_L x U(3)_R chiral sigma model
• QCD thermodynamics on the lattice