Magnetized baryons and the QCD phase diagram: NJL model meets the lattice

Abstract

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.

Quantum chromodynamics axion in a hot and magnetized medium

“…The dominance of sea contributions over the valence contributions of the condensate around T c is one of the probable reasons [64] behind the IMC. After the recognition of the presence of IMC through lattice QCD for both chiral and deconfinement transitions [64,65], several attempts have been made to understand it through different effective QCD models [49,55,59,[66][67][68][69][70][71][72][73]. At this point we want to emphasize that in the present work we will be discussing about both the effects of MC and IMC and the way of incorporating them in the axion thermodynamic potential, which is one of the novel features related to the present work.…”

Magnetic field dependent ’t Hooft determinant extended Nambu–Jona-Lasinio model

“…More recently, in Ref. [24], the constituent quark masses were calculated as a function of the magnetic field, B, using LQCD simulations and then the coupling GðBÞ was set to reproduce those constituent quark masses. It is important to remark that this new way to set GðBÞ was made within the SU(2) version of the Polyakov-Nambu-Jona-Lasinio model using the proper time formalism.…”

“…In the present paper we aim to apply the method proposed in [24] to the more laborious SU(3) version of the 't Hooft extended NJL model (which will henceforth be referred to as the NJL model), where now, due to the 't Hooft six fermions interactions that appear in the model, we have to set two couplings, the scalar coupling, GðBÞ, and the six fermions coupling, κðBÞ. 1 Also, in this application we consider the more general nondegenerate case m u ≠ m d ≠ m s .…”

“…For the fit of the parameters we follow the procedure: first we fit the six parameters of the model, Λ, G, κ, m u , m d and m s at T ¼ B ¼ 0; then, at B ≠ 0 the couplings G and κ are set to reproduce M d and M s magnetized constituent quark masses respectively, calculated in [24], while the other parameters are kept B independent. The other constituent quark mass, M u , is an output in our procedure.…”

“…In Sec. III we fit the parameters of the model to reproduce LQCD results [24], and we present the respective analysis of our results. Finally, in Sec.…”