arxiv: 2604.24535 · v1 · submitted 2026-04-27 · ✦ hep-ph · nucl-th

Recognition: unknown

Non-perturbative heavy quark diffusion coefficients in arbitrarily magnetized quark-gluon plasma

Aritra Bandyopadhyay, Debarshi Dey, Santosh K. Das, Yifeng Sun

Authors on Pith no claims yet

Pith reviewed 2026-05-08 02:58 UTC · model grok-4.3

classification ✦ hep-ph nucl-th

keywords heavy quark diffusionquark-gluon plasmamagnetic fieldnon-perturbative effectsspatial diffusion coefficientmomentum diffusion coefficientanisotropyLangevin dynamics

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The pith

Momentum diffusion of heavy quarks becomes anisotropic in magnetized quark-gluon plasma even in the static limit.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The authors calculate the momentum diffusion coefficients for heavy quarks moving through a hot quark-gluon plasma that contains a magnetic field of arbitrary strength. They include non-perturbative physics by using an in-medium potential extracted from a resummed gluon propagator. The key result is that these coefficients develop anisotropy aligned with the magnetic field direction because the spectral function of gluons limits momentum transfer along the field. Consequently, the spatial diffusion coefficient splits into distinct values parallel and perpendicular to the field. Non-perturbative contributions become the leading term at low temperatures, improving the modeling of heavy quark motion in collision experiments.

Core claim

We find that the momentum diffusion coefficients become anisotropic even in the static heavy quark limit, with the magnetic field direction defining the axis of anisotropy. This anisotropy originates from restrictions on longitudinal momentum diffusion in the gluon spectral function, and naturally leads to two spatial diffusion coefficients (D_s^L, D_s^T). Non-perturbative effects are found to be dominant at low temperatures. These results provide a more consistent input for Langevin based calculations of the heavy quark directed flow at RHIC and LHC energies.

What carries the argument

The in-medium heavy quark potential obtained from the resummed gluon propagator, which incorporates perturbative and non-perturbative effects at arbitrary magnetic field strength and sets the gluon spectral function for the diffusion calculation.

If this is right

Momentum diffusion coefficients develop anisotropy with the magnetic field direction as the symmetry axis.
Two separate spatial diffusion coefficients appear, one longitudinal and one transverse to the field.
Non-perturbative effects dominate the values of the diffusion coefficients at low temperatures.
The resulting anisotropic coefficients supply input parameters for Langevin simulations of heavy quark directed flow.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

The anisotropy could produce observable differences in heavy quark directed flow parallel versus perpendicular to the reaction plane in non-central collisions.
Splitting of the diffusion coefficients may change estimates of the time required for heavy quarks to thermalize in magnetized plasma.
Analogous magnetic-field-induced splitting could appear in other transport coefficients such as electrical conductivity of QCD matter.

Load-bearing premise

The in-medium heavy quark potential obtained from the resummed gluon propagator accurately incorporates both perturbative and non-perturbative effects for arbitrary magnetic field strength.

What would settle it

A lattice computation of the heavy quark diffusion tensor in a magnetic field at low temperature that finds no anisotropy between longitudinal and transverse directions would disprove the central claim.

read the original abstract

Heavy quark (HQ) momentum ($\kappa$) and spatial diffusion ($D_s$) coefficients are computed in a non-perturbative thermal QCD medium in the presence of a background magnetic field of arbitrary strength. Both perturbative and non-perturbative effects are incorporated via the in-medium HQ potential, obtained from the resummed gluon propagator. We find that the momentum diffusion coefficients become anisotropic even in the static heavy quark limit, with the magnetic field direction defining the axis of anisotropy. This anisotropy originates from restrictions on longitudinal momentum diffusion in the gluon spectral function, and naturally leads to two spatial diffusion coefficients ($D_s^L$, $D_s^T$). Non-perturbative effects are found to be dominant at low temperatures. These results provide a more consistent input for Langevin based calculations of the heavy quark directed flow at RHIC and LHC energies.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

The paper derives anisotropic heavy quark diffusion coefficients for arbitrary magnetic fields via a resummed gluon propagator, with the anisotropy arising even in the static limit from spectral function restrictions.

read the letter

The main point is that momentum diffusion coefficients become anisotropic in a magnetized QGP even for static heavy quarks, with the field direction as the axis. This follows from limits on longitudinal momentum transfer in the gluon spectral function and produces two spatial diffusion coefficients, D_s^L and D_s^T. Non-perturbative effects dominate at low temperatures, and the results are meant as inputs for Langevin calculations of directed flow at RHIC and LHC energies. The approach unifies perturbative and non-perturbative pieces through the in-medium heavy quark potential extracted from the resummed propagator, which extends earlier work limited to weak or strong field regimes separately. That unification is the clearest advance here, and the anisotropy claim tracks directly from the spectral function without obvious internal contradictions. The calculation appears consistent on its own terms and supplies a concrete way to handle realistic field strengths in transport models. The soft spots are minor but real. The description provides no explicit error estimates, numerical cross-checks against the zero-field limit, or direct comparisons to lattice data. The central assumption that the resummed potential captures both perturbative and non-perturbative physics accurately for any B strength is taken as given rather than tested in detail. No parameter-free derivations or machine-checked steps are claimed, which is typical for this style of work but leaves the quantitative outputs open to later scrutiny. This paper is for specialists in heavy quark transport and magnetized QGP phenomenology. Readers who run Langevin simulations or extract QGP properties from flow observables will find the two distinct spatial coefficients directly usable. It deserves a serious referee because the method rests on established techniques, the anisotropy is a sharp and falsifiable outcome, and the gap it fills is genuine even if the manuscript would benefit from added validation sections.

Referee Report

0 major / 2 minor

Summary. The manuscript computes non-perturbative heavy quark momentum diffusion coefficients (κ) and spatial diffusion coefficients (D_s) in a thermal QCD medium with a background magnetic field of arbitrary strength. Both perturbative and non-perturbative effects are incorporated through the in-medium heavy quark potential obtained from the resummed gluon propagator. The central result is that the momentum diffusion coefficients become anisotropic even in the static heavy quark limit, with the magnetic field direction as the anisotropy axis; this originates from restrictions on longitudinal momentum diffusion in the gluon spectral function and yields two distinct spatial diffusion coefficients D_s^L and D_s^T. Non-perturbative effects dominate at low temperatures, supplying improved inputs for Langevin-based calculations of heavy quark directed flow at RHIC and LHC energies.

Significance. If the results hold, the work provides a valuable unified framework for heavy quark transport in magnetized QGP that consistently includes non-perturbative physics at arbitrary B without additional free parameters. The finding of anisotropy in the static limit arising directly from the gluon spectral function, together with the dominance of non-perturbative contributions at low T, offers relevant input for modeling heavy-ion collision observables. The reliance on the resummed gluon propagator to encode both regimes is a clear strength.

minor comments (2)

The abstract states that anisotropy 'originates from restrictions on longitudinal momentum diffusion in the gluon spectral function' but does not indicate the explicit functional form or the step that maps this restriction onto the anisotropic κ; a brief clarifying sentence would improve readability.
Notation for the two spatial diffusion coefficients is introduced as D_s^L and D_s^T; a short parenthetical definition of the longitudinal and transverse directions relative to B would aid clarity on first use.

Simulated Author's Rebuttal

0 responses · 0 unresolved

We thank the referee for their positive assessment of our manuscript and for recommending minor revision. The referee's summary correctly identifies the central results: the emergence of anisotropy in the heavy-quark momentum diffusion coefficients even in the static limit, its origin in the longitudinal gluon spectral function, the consequent splitting into D_s^L and D_s^T, and the dominance of non-perturbative contributions at low temperature. We are pleased that the unified treatment via the resummed gluon propagator is viewed as a strength.

Circularity Check

0 steps flagged

No significant circularity; derivation self-contained

full rationale

The paper computes momentum and spatial diffusion coefficients from the in-medium heavy quark potential extracted from the resummed gluon propagator, which serves as an external input encoding both perturbative and non-perturbative physics. The reported anisotropy in the static limit is derived from restrictions on longitudinal momentum diffusion within the gluon spectral function, without any reduction of the output quantities back to fitted parameters or self-referential definitions within the paper's equations. No load-bearing self-citations, ansatzes smuggled via prior work, or renaming of known results are evident in the derivation chain; the central claims remain independent of the paper's own outputs.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

Central claim rests on the domain assumption that the resummed gluon propagator supplies a potential capturing both perturbative and non-perturbative physics at arbitrary B; no free parameters or invented entities are mentioned in the abstract.

axioms (1)

domain assumption The resummed gluon propagator provides the in-medium HQ potential that captures both perturbative and non-perturbative effects for arbitrary magnetic field.
Directly invoked in the abstract as the basis for the entire computation.

pith-pipeline@v0.9.0 · 5452 in / 1222 out tokens · 80856 ms · 2026-05-08T02:58:24.814934+00:00 · methodology

discussion (0)

Reference graph

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