QCD phase diagram in a constant magnetic background
Inverse magnetic catalysis: where models meet the lattice
Department of Physics, Norwegian University of Science and Technology, Høgskoleringen 5, 7491, Trondheim, Norway
Accepted: 13 May 2021
Published online: 9 June 2021
Magnetic catalysis is the enhancement of a condensate due to the presence of an external magnetic field. Magnetic catalysis at is a robust phenomenon in low-energy theories and models of QCD as well as in lattice simulations. We review the underlying physics of magnetic catalysis from both perspectives. The quark-meson model is used as a specific example of a model that exhibits magnetic catalysis. Regularization and renormalization are discussed and we pay particular attention to a consistent and correct determination of the parameters of the Lagrangian using the on-shell renormalization scheme. A straightforward application of the quark-meson model and the NJL model leads to the prediction that the chiral transition temperature is increasing as a function of the magnetic field B. This is in disagreement with lattice results, which show that is a decreasing function of B, independent of the pion mass. The behavior can be understood in terms of the so-called valence and sea contributions to the quark condensate and the competition between them. We critically examine these ideas as well recent attempts to improve low-energy models using lattice input.
© The Author(s) 2021
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