Critical point in the QCD phase diagram for extremely strong background magnetic fields

Endrődi, Gergely

doi:10.1007/jhep07(2015)173

Cited by 130 publications

(110 citation statements)

References 92 publications

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“…Under an increase of the magnetic field, the CEP eventually moves toward μ B ¼ 0, and the deconfinement and chiral phase transitions should become of first order as predicted by lattice calculations [49].…”

Section: The Influence Of the Magnetic Field On The Isentropic Tramentioning

confidence: 78%

Influence of the vector interaction and an external magnetic field on the isentropes near the chiral critical end point

Costa

2016

Phys. Rev. D

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The location of the critical end point (CEP) and the isentropic trajectories in the QCD phase diagram are investigated. We use the (2 þ 1) Nambu-Jona-Lasinio model with the Polyakov loop coupling for different scenarios, namely by imposing zero strange quark density, which is the case in the ultrarelativistic heavy ion collisions, and β equilibrium. The influence of strong magnetic fields and of the vector interaction on the isentropic trajectories around the CEP is discussed. It is shown that the vector interaction and the magnetic field, having opposite effects on the first-order transition, affect the isentropic trajectories differently: as the vector interaction increases, the first-order transition becomes weaker and the isentropes become smoother; when a strong magnetic field is considered, the first-order transition is strengthened and the isentropes are pushed to higher temperatures. No focusing of isentropes in region towards the CEP is seen.

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Section: The Influence Of the Magnetic Field On The Isentropic Tramentioning

confidence: 78%

Influence of the vector interaction and an external magnetic field on the isentropes near the chiral critical end point

Costa

2016

Phys. Rev. D

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“…Nevertheless, external magnetic field effects are best included through the Schwinger Proper-Time representation of the fermion propagator. This observation has been exploited to address the problem of magnetic catalysis [12] and inverse magnetic catalysis observed in lattice simulations [13,14] and confirmed by several approaches [7,8,15]. Under this environment, the effective coupling of the model can reach very large values, and therefore, exploring the validity of these regularization schemes in this super-strong coupling regime is a natural question to address.…”

Section: Introductionmentioning

confidence: 76%

On the iterative solution of the gap equation in the Nambu-Jona-Lasinio model

Martínez

Raya

2017

J. Phys.: Conf. Ser.

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Abstract. In this work we revise the standard iterative procedure to find the solution of the gap equation in the Nambu-Jona-Lasinio model within the most popular regularization schemes available in literature in the super-strong coupling regime. We observe that whereas for the hard cut-off regularization schemes, the procedure smoothly converges to the physically relevant solution, Pauli-Villars and Proper-Time regularization schemes become chaotic in the sense of discrete dynamical systems. We call for the need of an appropriate interpretation of the non-convergence of this procedure to the solution of the gap equation. IntroductionThe Nambu-Jona-Lasinio (NJL) model [1, 2] was one of the earliest attempts to describe strong interactions among protons and neutrons. Spontaneous breaking of chiral symmetry is presented in the model through an analogy with the phenomenon of superconductivity in condensed matter physics. The model has a single coupling constant for two kinds of 4-Fermi interactions and is non-renormalizable, which demands for a regulator. Nevertheless, up to date, the model continues being used as an effective description of quarks dynamics either as originally proposed, where fermion fields are now regarded as quark fields, or with slightly modifications [3, 4, 5] to account for confinement. NJL model has been widely used to sketch the quantum chromodynamics (QCD) phase diagram (see, for instance, Ref.[6] for a review) and its magnetized extension [7] from a complementary point of view of lattice [8] and other quantum field theoretical approaches [9,10]. Several regularization schemes have been used in literature within the context of NJL model. Perhaps the simplest regulator one can think of is to establish a hard cut-off in the four-momentum integrals, or over the spatial momentum integrals, which thus allows a straightforward incorporation of temperature and density effects within the Matsubara formalism [11]. Pauli-Villars regularization has also been used in NJL studies due to the advantages of the scheme. Nevertheless, external magnetic field effects are best included through the Schwinger Proper-Time representation of the fermion propagator. This observation has been exploited to address the problem of magnetic catalysis [12] and inverse magnetic catalysis observed in lattice simulations [13,14] and confirmed by several approaches [7,8,15]. Under this environment, the effective coupling of the model can reach very large values, and therefore,

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“…6: Plots of the critical temperature against eB, TC0 = 160MeV. We show the best fit lattice data taken from [8] and the holographic models best fit to that data (κ = 0.05, a = 0, b = 0.037). We also show the holographic models prediction for another value of b = 0.33 -the model depends on the quantity bB 2 so the eB axis is simply rescaled by this change.…”

Section: Magnetic Fieldmentioning

confidence: 95%

“…Recent lattice studies of QCD with light quarks and an applied magnetic field [6][7][8] have revealed some surprisingly complex behaviour. At zero temperature the magnetic field enhances the chiral condensate σ ≡ qq -"magnetic catalysis" -as has generally been predicted [9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Inverse magnetic catalysis in bottom-up holographic QCD

2016

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We explore the effect of magnetic field on chiral condensation in QCD via a simple bottom up holographic model which inputs QCD dynamics through the running of the anomalous dimension of the quark bilinear. Bottom up holography is a form of effective field theory and we use it to explore the dependence on the coefficients of the two lowest order terms linking the magnetic field and the quark condensate. In the massless theory, we identify a region of parameter space where magnetic catalysis occurs at zero temperature but inverse magnetic catalysis at temperatures of order the thermal phase transition. The model shows similar non-monotonic behaviour in the condensate with B at intermediate T as the lattice data. This behaviour is due to the separation of the meson melting and chiral transitions in the holographic framework. The introduction of quark mass raises the scale of B where inverse catalysis takes over from catalysis until the inverse catalysis lies outside the regime of validity of the effective description leaving just catalysis.

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Critical point in the QCD phase diagram for extremely strong background magnetic fields

Cited by 130 publications

References 92 publications

Influence of the vector interaction and an external magnetic field on the isentropes near the chiral critical end point

Influence of the vector interaction and an external magnetic field on the isentropes near the chiral critical end point

On the iterative solution of the gap equation in the Nambu-Jona-Lasinio model

Inverse magnetic catalysis in bottom-up holographic QCD

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