QCD in magnetic field, Landau levels and double-life of unbroken center-symmetry

Abstract

We study the thermal confinement/deconfinement and non-thermal quantum phase transitions or rapid cross-overs in QCD and QCD-like theories in external magnetic fields. At large magnetic fields, while the contribution of gauge fluctuations to Wilson-line potential remains unaltered at one-loop order, the contribution of fermions effectively becomes two lower dimensional and is enhanced by the density of states of the lowest Landau level (LLL). In a spatial compactification and for heavy adjoint fermions, this enhancement leads to a calculable zero temperature quantum phase transition on R^3*S^1 driven by a competition between the center-destabilizing gauge contribution and center-stabilizing LLL fermions. We also show that at a (formal) asymptotically large magnetic field, the adjoint fermions with arbitrarily large but fixed mass stabilize the center symmetry. This is an exotic case of simultaneous non-decoupling of large mass fermions (due to the enhancement by the LLL density of states) and decoupling from the low energy effective field theory. This observation has important implications for both Hosotani mechanism, for which gauge symmetry "breaking" occurs, and large-N volume independence (Eguchi-Kawai reduction), for which gauge structure is never "broken". Despite sounding almost self-contradictory, we carefully explain the physical scales entering the problem, double-meaning of unbroken center symmetry and how a clash is avoided. We also identify, for both thermal and spatial compactification, the jump in magnetic susceptibility as an order parameter for the deconfinement transition. The predictions of our analysis are testable by using current lattice techniques.

23 pages, 2 figures

References in corpus (14)

• The Chiral Magnetic Effect
• Charge separation induced by P-odd bubbles in QCD matter
• SU(N) gauge theories at large N
• QCD Phase Transition in a Strong Magnetic Background
• Center-stabilized Yang-Mills theory: confinement and large $N$ volume independence
• Magnetic bion condensation: A new mechanism of confinement and mass gap in four dimensions
• Volume independence in large Nc QCD-like gauge theories
• Chiral Properties of Strong Interactions in a Magnetic Background
• Finite size phase transitions in QCD with adjoint fermions
• (In)validity of large N orientifold equivalence
• Magnetic Susceptibility of Strongly Interacting Matter across the Deconfinement Transition
• Polyakov loops and the Hosotani mechanism on the lattice
• Introductory lectures to large-N QCD phenomenology and lattice results
• Monte Carlo Algorithms For Reduced Lattices, Mixed Actions, And Double-Trace Deformations

Cited by in corpus (6)

• Bjorken flow in one-dimensional relativistic magnetohydrodynamics with magnetization
• QCD phase diagram in a magnetic background for different values of the pion mass
• Magnetic susceptibility of a strongly interacting thermal medium with 2+1 quark flavors
• Classification of compactified $su(N_c)$ gauge theories with fermions in all representations
• Phases of circle-compactified QCD with adjoint fermions at finite density
• Superconductivity at Any Temperature