#### Deconfinement transitions of large N QCD with chemical potential at weak and strong coupling

- Event time: 2:00pm
- Event date: 7th November 2012
- Speaker: Joyce Myers (Niels Bohr Institute, Copenhagen)
- Location: Lecture Theatre A, James Clerk Maxwell Building (JCMB) James Clerk Maxwell Building Peter Guthrie Tait Road Edinburgh EH9 3FD GB

### Event details

QCD at non-zero chemical potential provides a description of systems with a quark-antiquark asymmetry, yet it is a description which is currently not directly accessible since it occurs at strong coupling and the non-zero chemical potential leads to a complex action, giving rise to the well-known sign problem. What this means is that the conventional techniques of studying finite temperature QCD: conventional lattice simulations and ordinary perturbation theory, are not applicable. In this talk we consider two nonconventional perturbative techniques which allow us to calculate the partition function and related observables such as the Polyakov line deconfinement order parameter and quark number, and from these to map out the phase diagram for an otherwise inaccessible range of temperatures and chemical potentials. We calculate the QCD phase diagram at large Nc and large Nf as a function of the temperature and chemical potential in the weak coupling and strong coupling limits. At weak coupling the relevant observables are calculated using 1-loop perturbation theory for QCD formulated on S^1 x S^3. At strong coupling the calculations are performed at leading order in the lattice strong coupling and hopping parameter expansions. We show that the matrix models in these two limits agree at temperatures and chemical potentials which are not too high, such that observables in the strongly-coupled theory can be obtained from the observables in the weakly-coupled theory, and vice versa, using a simple transformation of variables.

The Particle Physics Theory seminar is a weekly series of talks reflecting the diverse interests of the group. Topics include analytic and numerical calculations based on the Standard Model of elementary particle physics, theories exploring new physics, as well as more formal developments in gauge theories and gravity..