Related papers: QCD at Large $\theta$ Angle and Axion Cosmology
Taking into account the quadratic in mass terms in the effective chiral lagrangian, we show that, at \theta \sim \pi, the theory with 2 light quarks of equal mass involves two degenerate vacuum states separated by a barrier. For three…
We consider the quark-mass dependence of the baryon octet and decuplet ground state masses. It is predicted that QCD dynamics implies a first order transition when increasing the strange quark mass from its chiral limit towards its physical…
I discuss the global structure of the strongly interacting gauge theory of quarks and gluons as a function of the quark masses and the CP violating parameter $\theta$. I concentrate on whether a first order phase transition occurs at…
The partition function of QCD is analyzed for an arbitrary number of flavors, N_f, and arbitrary quark masses including the contributions from all topological sectors in the Leutwyler--Smilga regime. For given N_f and arbitrary vacuum…
We suggest an anomalous effective Lagrangian which reproduces the anomalous conformal and chiral Ward identities and topological charge quantization in QCD. It is shown that the large N_c Di Vecchia-Veneziano-Witten effective chiral…
We discuss the role of the U(1) axial symmetry for the phase structure of QCD at finite temperature. In particular, supported by recent lattice results, we analyse a scenario in which a U(1)-breaking condensate survives across the chiral…
Using the well-known low-energy effective Lagrangian of QCD --valid for small (non-vanishing) quark masses and a large number of colors-- we study in detail the regions of parameter space where $CP$ is spontaneously broken/unbroken for a…
We discuss the role of the U(1) axial symmetry for the phase structure of QCD at finite temperature. We expect that, above a certain critical temperature, also the U(1) axial symmetry will be (effectively) restored. We will try to see if…
We study the QCD vacuum orientation angles in correlation with the strong CP phases. A vacuum alignment equation of the dynamical chiral symmetry breaking is derived based on the anomalous Ward identity. It is emphasized that a chiral…
I discuss the mass parameters appearing in the gauge theory of the strong interactions, concentrating on the two flavor case. I show how the effect of the CP violating parameter $\theta$ is simply interpreted in terms of the state of the…
At low energies, the strong interaction is governed by the Goldstone bosons associated with the spontaneous chiral symmetry breaking, which can be systematically described by chiral perturbation theory. In this paper, we apply this theory…
Theta vacuum effects on the QCD phase structure in the \mu-T plane are studied by using the Polyakov-loop extended Nambu-Jona-Lasinio model and its extension, where \mu is the quark chemical potential and T is temperature, respectively. As…
We investigate the properties of QCD axion at low temperature and moderate density in the Nambu-Jona-Lasinio model with instanton induced interactions by simultaneously considering the scalar and pseudo-scalar condensates in both…
This paper addresses two aspects concerning the $\theta$-vacuum of Quantum Chromodynamics. First, large-$N_c$ chiral perturbation theory is used to calculate the first two non-trivial cumulants of the distribution of the winding number,…
A model for the QCD vacuum based on domain-like background gluon fields has previously been developed and demonstrated to exhibit confinement of quarks and strong correlation of the local chirality of quark modes and duality of the…
We study the effects of the interaction between the Chiral condensate and the Polyakov loop on the chiral transition within an effective Lagrangian. We find that the effects of the interaction change the order of the phase transition when…
We study QCD with three degenerate flavors of dynamical quarks using first-principles lattice simulations. For a specific choice of imaginary isospin chemical potential, this theory possesses an exact center symmetry, just like pure gauge…
We investigate the phase structure of QCD with 3 degenerate quark flavors as function of the degenerate quark masses at vanishing baryon number density. We use the Highly Improved Staggered Quarks on lattices with temporal extent $N_{t}=6$…
The nature of the QCD chiral phase transition in the limit of vanishing quark masses has remained elusive for a long time, since it cannot be simulated directly on the lattice and is strongly cutoff-dependent. We report on a comprehensive…
The temperature dependence of quark and gluon condensates in QCD as precursor of the chiral and deconfining phase transition is modelled with a conformally extended non-linear sigma-model including broken chiral and scale invariance. The…