Abstract:We investigate the QCD phase diagram for nonzero background magnetic fields using first-principles lattice simulations. At the physical point (in terms of quark masses), the thermodynamics of this system is controlled by two opposing effects: magnetic catalysis (enhancement of the quark condensate) at low temperature and inverse magnetic catalysis (reduction of the condensate) in the transition region. While the former is known to be robust and independent of the details of the interactions, inverse catalysis … Show more
“…This mechanism is suppressed if quarks are heavy. Indeed, contrary to the situation at the physical point, for sufficiently heavy quarks (M π 500 MeV), inverse magnetic catalysis does not occur anymore [17] -nevertheless, the transition temperature is still reduced by B [18].…”
We determine the baryon spectrum of 1 + 1 + 1-flavor QCD in the presence of strong background magnetic fields using lattice simulations at physical quark masses for the first time. Our results show a splitting within multiplets according to the electric charge of the baryons and reveal, in particular, a reduction of the nucleon masses for strong magnetic fields. This first-principles input is used to define constituent quark masses and is employed to set the free parameters of the Polyakov loop-extended Nambu-Jona-Lasinio (PNJL) model in a magnetic field-dependent manner. The so constructed model is shown to exhibit inverse magnetic catalysis at high temperatures and a reduction of the transition temperature as the magnetic field grows -in line with non-perturbative lattice results. This is contrary to the naive variant of this model, which gives incorrect results for this fundamental phase diagram. Our findings demonstrate that the magnetic field dependence of the PNJL model can be reconciled with the lattice findings in a systematic way, employing solely zero-temperature first-principles input.
“…This mechanism is suppressed if quarks are heavy. Indeed, contrary to the situation at the physical point, for sufficiently heavy quarks (M π 500 MeV), inverse magnetic catalysis does not occur anymore [17] -nevertheless, the transition temperature is still reduced by B [18].…”
We determine the baryon spectrum of 1 + 1 + 1-flavor QCD in the presence of strong background magnetic fields using lattice simulations at physical quark masses for the first time. Our results show a splitting within multiplets according to the electric charge of the baryons and reveal, in particular, a reduction of the nucleon masses for strong magnetic fields. This first-principles input is used to define constituent quark masses and is employed to set the free parameters of the Polyakov loop-extended Nambu-Jona-Lasinio (PNJL) model in a magnetic field-dependent manner. The so constructed model is shown to exhibit inverse magnetic catalysis at high temperatures and a reduction of the transition temperature as the magnetic field grows -in line with non-perturbative lattice results. This is contrary to the naive variant of this model, which gives incorrect results for this fundamental phase diagram. Our findings demonstrate that the magnetic field dependence of the PNJL model can be reconciled with the lattice findings in a systematic way, employing solely zero-temperature first-principles input.
“…[68] to use the temperaturedependent masses and then include additional logarithm terms in Eq. (30), which are vanishing in the original calculation. These temperature-dependent masses m f (b) (T ) and Polyakov-loop Φ(T ) can be obtained from FRG approach, we can thus substitute the results into the above formulas and do the integrals numerically.…”
Section: Calculations and Resultsmentioning
confidence: 96%
“…Magnetic susceptibility χ(T ) has also been studied by combining the FRG approach with the non-interacting gas approximation in Refs. [68,103], in which the whole system is approximated as non-interacting quark and (pseudo-)scalar meson gases [30]. χ(T ) can then be separated into two parts, namely…”
Section: Calculations and Resultsmentioning
confidence: 99%
“…It has been well known that the equation of state (EoS) and the entropy density can represent well the properties of a matter. Then the EoS and the entropy density of the strong interaction matter in an external magnetic field have been studied with the lattice QCD simulations [27][28][29], Hadron Resonance Gas (HRG) model [30], quark-meson (QM) model [67,68,88] and Polyakov-loop improved quark-meson (PQM) model [10-13, 59, 89-93]. However, the mechanism of the magnetic field effect on the QCD system has not yet been fully understood by analyzing the thermodynamical properties concretely.…”
We study the thermodynamics of QCD system under external magnetic field via the 2+1 flavor Polyakov-loop quark-meson model. To incorporate quantum and thermal fluctuations, the functional renormalization group approach is implemented in our work. Pressure, entropy density, magnetic susceptibility and other thermodynamic quantities are calculated and analyzed to investigate the effect of magnetic field on the QCD system. The calculated results are in reasonable agreement with lattice QCD simulations and perturbation theory. We then give an intuitive picture for the response of QCD system to the magnetic field.
“…Meanwhile general analysis and effective QCD models have also played the important role and made significant progress (see, e.g., Refs. [4,5,6,57,58,59,60,61,62,63,64,65,66]).…”
Section: Qcd Phase Transitions and The Phase Diagrammentioning
We investigate the chemical potential and baryon number density of the hadron-quark phase transition in neutron star matter. The hadron matter is described with the relativistic mean field theory, and the quark matter is described with the Dyson-Schwinger equation approach of QCD. In order to study the first-order phase transition, we develop the sound speed interpolation scheme to construct the equation of state in the middle density region where the hadron phase and quark phase coexist. The phase transition chemical potential is constrained with the maximum mass, the tidal deformability and the radius of neutrons stars. And the most probable value of the phase transition chemical potential is found. * Speaker.
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