Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userQCD phase diagram at finite baryon and isospin chemical potentials
282
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The phase structure of two-flavor QCD is explored for thermal systems with finite baryon- and isospin-chemical potentials, mu_B and mu_{iso}, by using the Polyakov-loop extended Nambu--Jona-Lasinio (PNJL) model. The PNJL model with the scalar-type eight-quark interaction can reproduce lattice QCD data at not only mu_{iso}=mu_B=0 but also mu_{iso}>0 and mu_B=0. In the mu_{iso}-mu_{B}-T space, where T is temperature, the critical endpoint of the chiral phase transition in the mu_B-T plane at mu_{iso}=0 moves to the tricritical point of the pion-superfluidity phase transition in the mu_{iso}-T plane at mu_B=0 as mu_{iso} increases. The thermodynamics at small T is controlled by sqrt{sigma^2+pi^2} defined by the chiral and pion condensates, sigma and pi.
rate research
Read More
We introduce a random matrix model with the symmetries of QCD at finite temperature and chemical potentials for baryon number and isospin. We analyze the phase diagram of this model in the chemical potential plane for different temperatures and quark masses. We find a rich phase structure with five different phases separated by both first and second order lines. The phases are characterized by the pion condensate and the chiral condensate for each of the flavors. In agreement with lattice simulations, we find that in the phase with zero pion condensate the critical temperature depends in the same way on the baryon number chemical potential and on the isospin chemical potential. At nonzero quark mass, we remarkably find that the critical end point at nonzero temperature and baryon chemical potential is split in two by an arbitrarily small isospin chemical potential. As a consequence, there are two crossovers that separate the hadronic phase from the quark-gluon plasma phase at high temperature. Detailed analytical results are obtained at zero temperature and in the chiral limit.
We determine the (pseudo)critical lines of QCD with two degenerate staggered fermions at nonzero temperature and quark or isospin density, in the region of imaginary chemical potentials; analytic continuation is then used to prolongate to the region of real chemical potentials. We obtain an accurate determination of the curvatures at zero chemical potential, quantifying the deviation between the case of finite quark and of finite isospin chemical potential. Deviations from a quadratic dependence of the pseudocritical lines on the chemical potential are clearly seen in both cases: we try different extrapolations and, for the case of nonzero isospin chemical potential, confront them with the results of direct Monte Carlo simulations. Finally we find that, as for the finite quark density case, an imaginary isospin chemical potential can strengthen the transition till turning it into strong first order.
In this contribution we investigate the phase diagram of QCD in the presence of an isospin chemical potential. To alleviate the infrared problems of the theory associated with pion condensation, we introduce the pionic source as an infrared regulator. We discuss various methods to extrapolate the results to vanishing pionic source, including a novel method based on the singular value spectrum of the massive Dirac operator, a leading-order reweighting and a spline Monte-Carlo fit. Our main results concern the phase transition boundary between the normal and the pion condensation phases and the chiral/deconfinement transition temperature as a function of the chemical potential. In addition, we perform a quantitative comparison between our direct results and a Taylor-expansion obtained at zero chemical potential to assess the applicability range of the latter.
We investigate the properties of QCD at finite isospin chemical potential at zero and non-zero temperatures. This theory is not affected by the sign problem and can be simulated using Monte-Carlo techniques. With increasing isospin chemical potential and temperatures below the deconfinement transition the system changes into a phase where charged pions condense, accompanied by an accumulation of low modes of the Dirac operator. The simulations are enabled by the introduction of a pionic source into the action, acting as an infrared regulator for the theory, and physical results are obtained by removing the regulator via an extrapolation. We present an update of our study concerning the associated phase diagram using 2+1 flavours of staggered fermions with physical quark masses and the comparison to Taylor expansion. We also present first results for our determination of the equation of state at finite isospin chemical potential and give an example for a cosmological application. The results can also be used to gain information about QCD at small baryon chemical potentials using reweighting with respect to the pionic source parameter and the chemical potential and we present first steps in this direction.
The confinement-deconfinement transition is discussed from topological viewpoints. The topological change of the system is achieved by introducing the dimensionless imaginary chemical potential ($theta$). Then, the non-trivial free-energy degeneracy becomes the signal of the deconfinement transition and it can be visualized by using the map of the thermodynamic quantities to the circle $S^1$ along $theta$. To understand this topological deconfinement transition at finite real quark chemical potential ($mu_mathrm{R}$), we consider the isospin chemical potential ($mu_mathrm{iso}$) in the effective model of QCD. The phase diagram at finite $mu_mathrm{iso}$ is identical with that at finite $mu_mathrm{R}$ outside of the pion-condensed phase at least in the large-$N_mathrm{c}$ limit via the well-known orbifold equivalence. In the present effective model, the topological deconfinement transition does not show a significant dependence on $mu_mathrm{iso}$ and then we can expect that this tendency also appears at small $mu_mathrm{R}$. Also, the chiral transition and the topological deconfinement transition seems to be weakly correlated. If we will access lattice QCD data for the temperature dependence of the quark number density at finite $mu_mathrm{iso}$ with $theta=pi/3$, our surmise can be judged.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
