Abstract. We study SU(2) lattice gauge theory with two flavors of Wilson fermion at non-zero chemical potential µ and low temperature on a 8 3 × 16 system. We identify three régimes along the µ-axis. For µ mπ/2 the system remains in the vacuum phase, and all physical observables considered remain essentially unchanged. The intermediate régime is characterised by a non-zero diquark condensate and an associated increase in the baryon density, consistent with what is expected for Bose-Einstein condensation of tightly bound diquarks. We also observe screening of the static quark potential here. In the high-density deconfined régime we find a non-zero Polyakov loop and a strong modification of the gluon propagator, including significant screening in the magnetic sector in the static limit, which must have a non-perturbative origin. The behaviour of thermodynamic observables and the superfluid order parameter are consistent with a Fermi surface disrupted by a BCS diquark condensate. The energy per baryon as a function of µ exhibits a minimum in the deconfined régime, implying that macroscopic objects such as stars formed in this theory are largely composed of quark matter.

We study the temperature dependence of bottomonium for temperatures in the range 0.4Tc < T < 2.1Tc, using nonrelativistic dynamics for the bottom quark and full relativistic lattice QCD simulations for N f = 2 light flavors on a highly anisotropic lattice. We find that the Υ is insensitive to the temperature in this range, while the χ b propagators show a crossover from the exponential decay characterizing the hadronic phase to a power-law behaviour consistent with nearly-free dynamics at T ≃ 2Tc.

We present results on the bottomonium spectrum at temperatures above and below the deconfinement crossover temperature, T c , from dynamical lattice QCD simulations. The heavy quark is treated with a non-relativistic effective field theory on the lattice and serves as a probe of the hot medium. Ensembles with a finer spatial lattice spacing and a greater range of temperatures below T c than those previously employed by this collaboration are used. In addition, there are N f = 2 + 1 flavours of Wilson clover quark in the sea with M π ≈ 400 MeV and we perform a more careful tuning of the bottom quark mass in this work. We calculate the spectral functions of S and P wave bottomonium states using the maximum entropy method and confirm earlier findings on the survival of the ground state S wave states up to at least 2T c and the immediate dissociation of the P wave states above T c .

We study bottomonium spectral functions in the quark-gluon plasma in the Υ and η b channels, using lattice QCD simulations with two flavours of light quark on highly anisotropic lattices. The bottom quark is treated with nonrelativistic QCD (NRQCD). In the temperature range we consider, 0.42 ≤ T /T c ≤ 2.09, we find that the ground states survive, whereas the excited states are suppressed as the temperature is increased. The position and width of the ground states are compared to analytical effective field theory (EFT) predictions. Systematic uncertainties of the maximum entropy method (MEM), used to construct the spectral functions, are discussed in some detail.