What happens to protons and neutrons, the building blocks of Nature, when they are put at high temperature, as in the early Universe, or packed in high density, as inside a neutron star? A study of the strong nuclear force, described by Quantum Chromodynamics (QCD), should provide the answer.
Using numerical lattice QCD simulations, it has been found that at high temperature a phase transition to a new state of matter occurs, the quark-gluon plasma (QGP). The required temperatures were only present in the early Universe, but excitingly, in the past years these conditions have been recreated by colliding lead ions at the Large Hadron Collider at CERN.
Instead of raising the temperature, one can also pack more and more quarks together, as in neutron and quark stars. However, in that case it is no longer possible to perform numerical lattice QCD simulations, since Monte-Carlo based methods cease to work. Hence the phase structure of QCD at non-zero quark density has not yet been determined: an outstanding question in particle physics.
Here we study quarks and gluons under extreme conditions, using high- performance computing resources. We have recently demonstrated how to study dense systems, using an alternative to Monte-Carlo based algorithms. We want to establish this approach for QCD, and determine its phase structure for the first time.
To explore how elementary particles interact, under conditions prevalent in the early Universe, is fascinating both for scientists and the general public. Moreover, theoretical predictions can now be compared with experiments at the LHC, a truly unique opportunity. The problems addressed here are particularly challenging, since physics questions are combined with technological advances in the field of high-performance computing and algorithmic breakthroughs. In this project we combine therefore fundamental science at the forefront of research with advanced technological input, an exciting possibility!
Interests and expertise (Subject groups)