QGP universality in a magnetic field?

Abstract

We use top-down holographic models to study the thermal equation of state of strongly coupled quark-gluon plasma in external magnetic field. We identify different conformal and non-conformal theories within consistent truncations of \( \mathcal{N} \) = 8 gauged supergravity in five dimensions (including STU models, gauged \( \mathcal{N} \) = 2* theory) and show that the ratio of the transverse to the longitudinal pressure PT /PL as a function of T /\( \sqrt{B} \) can be collapsed to a ‘universal’ curve for a wide range of the adjoint hypermultiplet masses m. We stress that this does not imply any hidden universality in magnetoresponse, as other observables do not exhibit any universality. Instead, the observed collapse in PT /PL is simply due to a strong dependence of the equation of state on the (freely adjustable) renormalization scale: in other words, it is simply a fitting artifact. Remarkably, we do uncover a different universality in \( \mathcal{N} \) = 2* gauge theory in the external magnetic field: we show that magnetized \( \mathcal{N} \) = 2* plasma has a critical point at Tcrit/\( \sqrt{B} \) which value varies by 2% (or less) as m/\( \sqrt{B} \) ∈ [0, ∞). At criticality, and for large values of m/\( \sqrt{B} \), the effective central charge of the theory scales as ∝ \( \sqrt{B} \)/m.

A preprint version of the article is available at ArXiv.

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Correspondence to Bruno Umbert.

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Buchel, A., Umbert, B. QGP universality in a magnetic field?. J. High Energ. Phys. 2020, 149 (2020). https://doi.org/10.1007/JHEP06(2020)149

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Keywords

  • AdS-CFT Correspondence
  • Gauge-gravity correspondence
  • Holography and quark-gluon plasmas
  • Quark-Gluon Plasma