Abstract
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.
Highlights
The study of first principles QCD under extreme conditions is of vital importance to illuminate the properties of QCD dominated aspects of matter in the universe and for phenomenology to test and develop models which can be used to understand different aspects of matter surrounding us
The chiral condensate decreases strongly in the darker region on the right of the plot and one can clearly see a bend towards larger values of μI with increasing μB. In this proceedings article we have presented the current status of our study of QCD at finite isospin chemical potential with improved staggered fermions at physical quark masses
The most crucial step in the analysis, the extrapolation of the prefactor of the pionic source term λ → 0, has been done using the improvement scheme introduced in ref. [12], which we have briefly sketched in sec. 2.2
Summary
The study of first principles QCD under extreme conditions is of vital importance to illuminate the properties of QCD dominated aspects of matter in the universe and for phenomenology to test and develop models which can be used to understand different aspects of matter surrounding us. In this proceedings article we update these results by showing new results for Nt = 6 and first results from Nt = 8 and 10 lattices.
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