QGP universality in a magnetic field?

• Main Authors: Alex Buchel, Bruno Umbert
• Format: Article
• Language: English
• Published: SpringerOpen 2020-06-01
• Series: Journal of High Energy Physics
• Subjects: AdS-CFT Correspondence; Gauge-gravity correspondence; Holography and quark-gluon plasmas; Quark-Gluon Plasma
• Online Access: http://link.springer.com/article/10.1007/JHEP06(2020)149

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 N $$ \mathcal{N} $$ = 8 gauged supergravity in five dimensions (including STU models, gauged N $$ \mathcal{N} $$ = 2* theory) and show that the ratio of the transverse to the longitudinal pressure P T /P L as a function of T / B $$ \sqrt{B} $$ 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 P T /P L 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 N $$ \mathcal{N} $$ = 2* gauge theory in the external magnetic field: we show that magnetized N $$ \mathcal{N} $$ = 2* plasma has a critical point at T crit/ B $$ \sqrt{B} $$ which value varies by 2% (or less) as m/ B $$ \sqrt{B} $$ ∈ [0, ∞). At criticality, and for large values of m/ B $$ \sqrt{B} $$ , the effective central charge of the theory scales as ∝ B $$ \sqrt{B} $$ /m.