Which scale breaks quarkonium? A controlled comparison of density and momentum relaxation in holographic QCD
Year: 2026
Type: preprint
Abstract: In a quark-gluon plasma (QGP) that is both dense and dissipative, do static color screening and thermodynamic response follow the same medium scale? The question matters because heavy-quark observables are routinely used to infer QGP properties, yet in a background with only finite density, or only momentum relaxation, the two scales cannot be compared: one of them is absent. We use the Einstein-Maxwell-axion geometry, in which the chemical potential $μ$ and the translational-symmetry-breaking parameter $β$ enter as independent controls, to carry out this comparison at fixed temperature. The static potential, the thermal free energy, and the running coupling are computed with high numerical precision, and the zero-temperature limit is used to isolate the non-thermal response. The comparison reveals a hierarchy that is invisible when either scale is studied alone: $μ$ controls the potential and the running coupling through near-horizon color screening, while $β$ controls the thermal free energy through its imprint on horizon entropy. At $T=0$ the hierarchy persists in the dissociation scale, where finite density shortens the binding range far more efficiently than pure momentum relaxation. The geometric origin is that the $μ^2 z^4$ term grows toward the horizon and deforms the region that governs string screening, whereas the constant $β^2$ term shifts the horizon entropy without a comparable localized deformation. This separation yields a criterion for identifying which medium scale is at work in any holographic construction that contains both density and dissipation.
Source: arXiv (Cornell University)
Institution: China University of Geosciences
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Awards: G3487202357, G5334749420
OpenAlex ID: W7164940050