Thesis

Lattice QCD – unravelling the strong interaction with high performance computing

• Call:

  IDPASC Portugal - PHD Programme 2015

• Academic Year:

  2015 / 2016

• Domains:

  Theoretical Particle Physics | Cosmology

• Supervisor:

  Pedro Bicudo

• Co-Supervisor:

  Marina Marinkovic

• Institution:

  Instituto Superior Técnico

• Host Institution:

  CFTP

• Abstract:

  Quantum Chromodynamics (QCD) is the theory of quarks and gluons, sub-particles constituting most of the visible matter in the universe. Because QCD is non-perturbative, most Particle Physics techniques fail to solve QCD. The only known approach to eventually solve QCD is computing the Path Integral with Monte-Carlo techniques, e g Lattice QCD. We simulate tiny parts of the Universe at the femtometer scale with up to 100 million space-time points. The QCD theory of particles and fields, with non-commutative groups such as the SU(3) 'colour' gauge group and the broken global symmetries in the SU(6) 'flavours' u, d, s, c, b and t , is very beautiful from a mathematical perspective, and discretizing it on a lattice makes it even more interesting. However this is computationally very demanding, and Lattice QCD is also a High Performance Computing (HPC) topic. We utilize the most efficient computers we can find. In CFTP, IST, U. Lisboa, we have been developing codes in C++ and CUDA to run in Graphics Processing Units (GUPs). A GPU has up to 1000 cores and allows HPC in a workstation. We have several servers with state of the art GPUs, partly supported by NVIDIA grants. Our Lattice QCD students become outstanding programmers, able to solve the most difficult numerical problems a scientist may address. The lattice QCD students are usually able to find jobs not only in research but also in programming or finance companies. We are staring a new collaboration between the lattice QCD groups of CFTP, IST, University of Lisboa and of the Theory Division of CERN. The thesis will be jointly co-supervised by both teams. Moreover The thesis will benefit from other institutions. Our Lattice QCD group at CFTP has also been collaborating with the Lattice QCD groups of the University of Coimbra, and of the Wolfgang Goethe University of Frankfurt, researching open problems in Theoretical Physics and sharing computational facilities. With the University of Coimbra, we also manage joint projects, and apply to FCT grants and European Union (Horizon 2020) grants. Our Portuguese collaboration is PtQCD and the thesis will be developed with its support, http://nemea.ist.utl.pt/~ptqcd Many open problems remain to be solved in Lattice QCD, crucial to our understanding of Particle Physics and Cosmology. For the program of the thesis we propose different topics to the candidate, such as, - confinement, chiral symmetry, colour superconductivity and other possible phases existing at finite temperatures and densities, relevant for the studies of the early universe, of dark energy and of heavy ion collisions, - the missing part of the muon magnetic moment, relevant for the possible discovery of new particles beyond the standard model, - exotic bound states and resonances of quarks and gluons, such as hybrids, tetraquarks or glueballs, predicted a long time ago but still remaining to be understood.