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Journal of High Energy Physics

, 2014:107

First Online: 16 December 2014Received: 23 October 2014Accepted: 07 December 2014 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 \ {\mathbb{R}}^3\times {\mathbb{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.

KeywordsConfinement Field Theories in Lower Dimensions Phase Diagram of QCD Nonperturbative Effects ArXiv ePrint: 1309.4394

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Autor: Mohamed M. Anber - Mithat Ünsal

Fuente: https://link.springer.com/

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