Chiral soliton lattice in QCD-like theories
Peer reviewed, Journal article
Published version
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https://hdl.handle.net/11250/3046627Utgivelsesdato
2019Metadata
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Originalversjon
Brauner, T., Filios, G., & Kolešová, H. (2019). Chiral soliton lattice in QCD-like theories. Journal of High Energy Physics, 2019(12), 1-26. 10.1007/JHEP12(2019)029Sammendrag
Recently, it has been shown that the ground state of quantum chromodynamics (QCD) in suffciently strong magnetic fields and at moderate baryon number chemical potential carries a crystalline condensate of neutral pions: the chiral soliton lattice (CSL). While the result was obtained in a model-independent manner using effective field theory techniques, its realization from first principles using lattice Monte Carlo simulation is hampered by the infamous sign problem. Here we show that CSL, or a similar inhomogeneous phase, also appears in the phase diagram of a class of vector-like gauge theories that do not suffer from the sign problem even in the presence of a baryon chemical potential and external magnetic field. We also show that the onset of nonuniform order manifests itself already in the adjacent homogeneous Bose-Einstein-condensation phase through a characteristic roton-like minimum in the dispersion relation of the lowest-lying quasiparticle mode. Last but not least, our work gives a class of explicit counterexamples to the long-standing conjecture that positivity of the determinant of the Dirac operator (that is, absence of the sign problem) in a vector-like gauge theory precludes spontaneous breaking of translational invariance, and thus implies the absence of inhomogeneous phases in the phase diagram of the theory.