Abstract: Rapid advancement in neutron-star observations allows unprecedented empirical access to cold, ultra-dense QCD matter, complementing collider experiments. The combination of these observations with theoretical calculations reveals previously inaccessible features of the equation of state and the phase diagram of QCD. In this talk, I demonstrate how perturbative-QCD calculations at asymptotically high densities robustly constrain the equation of state at neutron-star densities using a new method solely based on causality and stability. I confront these calculations with neutron-star observations in a Gaussian-process-based Bayesian framework and demonstrate that the perturbative-QCD calculations offer significant and nontrivial information, going beyond that which is obtainable from current observations. The main effect of the QCD input is to soften the equation of state at high densities, supporting the hypothesis that most massive neutron stars have quark matter cores.

We present a QCD analysis of the effective weak Hamiltonian at hadronic energy scales for strangeness-nonchanging (∆S = 0) hadronic processes. Performing a leading-order renormalization group analysis in QCD from the weak to the O(2 GeV) energy scale, we derive the pertinent effective Hamiltonian for hadronic parity violation, including the effects of both neutral and charged weak currents. We compute the complete renormalization group evolution of all isosectors and the evolution through heavy-flavor thresholds for the first time. We show that the additional four-quark operators that enter below the electroweak scale from QCD operator mixing effects form a closed set, and they result in a 12×12 anomalous dimension matrix. We use the resulting effective Hamiltonian to determine the parity-violating meson-nucleon coupling constants, h^1_π , h^{ 0,1,2}_ ρ , h^{0,1}_ ω , employing the factorization Ansatz and assessments of the pertinent quark charges of the nucleon in lattice QCD at the 2 GeV scale. On this basis, we connect to earlier calculations of low-energy, hadronic parity-violating observables in few-nucleon systems to make theoretical predictions that we compare with recent experimental results, for a global view of the relative importance of the various isosectors. 

Heavy quarks and their bound states are ideal probes of the medium formed in heavy ion collisions.  The resulting hierarchy of scales of in-medium heavy quarkonium makes the combined system ideally suited for treatment using nonrelativistic effective field theories and the formalism of open quantum systems (OQS).  My talk will consist of three parts: in the first, I will present an introduction to nonrelativistic QCD (NRQCD), potential NRQCD (pNRQCD), and the OQS formalism; in the second, I will present the derivation of the master equation governing the evolution of in-medium heavy quarkonium; and in the third, I will discuss solutions of the master equation and present recent phenomenological results for the nuclear modification factor and the elliptic flow compared against experimental measurements.