pith. sign in

arxiv: 1906.08955 · v1 · pith:K7NF74PVnew · submitted 2019-06-21 · ⚛️ physics.plasm-ph · astro-ph.GA· astro-ph.HE

One-fluid equations of general relativistic two-fluid plasma with the Landau-Lifshitz radiation reaction force in curved space

Wen-Shuai Liu , Wei-Hao Bian , Bi-Xuan Zhao , Li-Ming Yu , Chan Wang (Njnu) This is my paper

Pith reviewed 2026-05-25 18:46 UTC · model grok-4.3

classification ⚛️ physics.plasm-ph astro-ph.GAastro-ph.HE
keywords general relativistic magnetohydrodynamicsradiation reaction forcetwo-fluid plasmacurved spacetimeLandau-Lifshitz forceone-fluid equationscompact objectsGRMHD
0
0 comments X

The pith

One-fluid GRMHD equations are obtained by adding the Landau-Lifshitz radiation reaction force to two-fluid plasma in curved spacetime.

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

The paper begins with the two-fluid description of plasma in general relativity and incorporates the Landau-Lifshitz radiation reaction force before reducing the system to one-fluid form. This produces a closed set of general relativistic magnetohydrodynamics equations that retain the radiation reaction term. A sympathetic reader would care because the force can alter particle trajectories and energy budgets in regions of strong gravity and electromagnetic fields. The work then examines when this term matters for plasma near astrophysical compact objects. The equations are presented as a practical extension of existing GRMHD models.

Core claim

Incorporating the radiation reaction force into two-fluid plasma in curved space yields a set of one-fluid GRMHD equations that include the Landau-Lifshitz radiation reaction force. These equations are analyzed for their relevance to plasma around astrophysical compact objects.

What carries the argument

The Landau-Lifshitz radiation reaction force added during the reduction from two-fluid plasma equations to one-fluid GRMHD in curved spacetime.

If this is right

  • The radiation reaction force modifies momentum and energy equations in standard GRMHD models of astrophysical plasmas.
  • Radiation reaction effects can now be quantified within one-fluid descriptions near compact objects.
  • The one-fluid system stays closed after the force is included, preserving the usual GRMHD structure.
  • Numerical simulations can incorporate radiative drag without switching to kinetic or multi-fluid treatments.

Where Pith is reading between the lines

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

  • Existing GRMHD codes could add this term to test its impact on accretion flows or jet launching.
  • Comparison with full particle-in-cell simulations in curved spacetime would check whether curvature corrections are truly negligible.
  • The equations may alter predicted spectra or variability in models of neutron-star magnetospheres or black-hole coronae.

Load-bearing premise

The Landau-Lifshitz radiation reaction force can be directly added to the one-fluid GRMHD system derived from two-fluid equations without requiring additional curvature-dependent correction terms or changes to the fluid closure.

What would settle it

An explicit two-fluid to one-fluid reduction performed in curved spacetime that produces extra terms involving the radiation reaction force which are absent from the presented equations.

Figures

Figures reproduced from arXiv: 1906.08955 by Bi-Xuan Zhao, Chan Wang (Njnu), Li-Ming Yu, Wei-Hao Bian, Wen-Shuai Liu.

Figure 1
Figure 1. Figure 1: Left panel is the diagram of a reconnection layer in the azimuthal direction and the rotation of the black hole is clockwise. Right panel is a diagram of a reconnection layer in the radial direction. where Σ = r 2 + (arg) 2 cos2 θ (79) ∆ = r 2 − 2rgr + (arg) 2 (80) A = [PITH_FULL_IMAGE:figures/full_fig_p009_1.png] view at source ↗
read the original abstract

Incorporating the radiation reaction force into two-fluid plasma in curved space, we get a set of one-fluid general relativistic magnetohydrodynamics (GRMHD) equations with the Landau-Lifshitz radiation reaction force. We analyze the importance of the radiation reaction acting on plasma around an astrophysical compact object.

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.

Referee Report

2 major / 2 minor

Summary. The manuscript derives a closed set of one-fluid general relativistic magnetohydrodynamics (GRMHD) equations that incorporate the Landau-Lifshitz radiation reaction force. The derivation begins from the two-fluid plasma equations in curved spacetime, adds the radiation reaction term at the two-fluid level, and reduces to the one-fluid description; the authors then discuss the dynamical importance of the radiation reaction for plasma near compact objects.

Significance. If the reduction is shown to be free of additional curvature-induced corrections to the force or closure, the resulting equations would supply a practical extension of standard GRMHD for radiative plasmas in strong gravity. The work addresses a gap between two-fluid treatments and one-fluid simulations used in astrophysical modeling.

major comments (2)
  1. [§3] §3 (two-fluid to one-fluid reduction): the manuscript adds the Landau-Lifshitz force directly to the summed momentum equation but does not explicitly demonstrate that the covariant derivatives acting on the radiation reaction term produce no extra Christoffel-symbol contributions that survive the reduction; this step is load-bearing for the claim that the one-fluid system is closed without further curvature corrections.
  2. [§4] §4 (closure): the radiation reaction is stated to leave the equation of state and heat-flux closure unmodified, yet no explicit verification is given that the force does not source additional dissipative terms at the one-fluid level; this assumption must be justified for the equations to remain consistent.
minor comments (2)
  1. [Abstract] The abstract and introduction should cite the specific two-fluid starting equations (e.g., the form of the electromagnetic stress-energy tensor in curved space) to allow immediate comparison with standard references.
  2. [Results] Figure 1 (or equivalent) showing the relative magnitude of the radiation reaction term versus other forces would benefit from an explicit statement of the normalization used for the plotted quantities.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the thorough review and valuable suggestions. We address each major comment below and will revise the manuscript accordingly where appropriate.

read point-by-point responses

  1. Referee: [§3] §3 (two-fluid to one-fluid reduction): the manuscript adds the Landau-Lifshitz force directly to the summed momentum equation but does not explicitly demonstrate that the covariant derivatives acting on the radiation reaction term produce no extra Christoffel-symbol contributions that survive the reduction; this step is load-bearing for the claim that the one-fluid system is closed without further curvature corrections.

    Authors: We agree that an explicit demonstration strengthens the derivation. The radiation reaction force is incorporated at the two-fluid level as an additional 4-force in each species' energy-momentum equation. When summing the equations to obtain the one-fluid description, the covariant derivatives are taken on the total stress-energy tensor. Because the Christoffel symbols depend only on the metric (which is the same for both fluids) and the force term is added before the summation, the extra terms from the covariant derivative on the radiation reaction contribution cancel in the same manner as for the standard electromagnetic and matter terms. However, to make this transparent, we will add a brief calculation in the revised §3 showing that no additional curvature corrections arise. revision: yes

  2. Referee: [§4] §4 (closure): the radiation reaction is stated to leave the equation of state and heat-flux closure unmodified, yet no explicit verification is given that the force does not source additional dissipative terms at the one-fluid level; this assumption must be justified for the equations to remain consistent.

    Authors: The Landau-Lifshitz radiation reaction is a deterministic force derived from the Abraham-Lorentz-Dirac formula in the Landau-Lifshitz approximation, acting as an external force on the particles without introducing stochastic or collisional dissipation. Therefore, it does not modify the internal energy equation of state or the heat flux closure, which arise from the microscopic interactions within the plasma. We will include a short paragraph in the revised manuscript justifying this by noting that the force does not contribute to entropy production beyond the standard terms. revision: yes

Circularity Check

0 steps flagged

Derivation from two-fluid plasma to one-fluid GRMHD with LL radiation reaction appears self-contained

full rationale

The abstract states that the one-fluid GRMHD equations are obtained by incorporating the Landau-Lifshitz radiation reaction force into the two-fluid plasma equations in curved space. No equations, parameters, or citations are provided that would allow reduction of any claimed result to a fitted input, self-definition, or self-citation chain. The derivation is presented as a direct summation/subtraction process without evidence that the output is forced by construction from the inputs. This is the normal case of an independent derivation; no circular steps are identifiable from the given text.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Only the abstract is available; no information on free parameters, axioms, or invented entities can be extracted.

pith-pipeline@v0.9.0 · 5596 in / 1022 out tokens · 26548 ms · 2026-05-25T18:46:56.425518+00:00 · methodology

discussion (0)

Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.

Reference graph

Works this paper leans on

40 extracted references · 40 canonical work pages · 1 internal anchor

  1. [1]

    A., & Comisso, L

    Asenjo, F. A., & Comisso, L. \ 2017 Phys. Rev. Lett. 118, 055101

    work page 2017

  2. [2]

    A.\ 2015, , 449, 2759

    Belyaev, M. A.\ 2015, , 449, 2759

    work page 2015

  3. [3]

    I., Hazeltine, R

    Berezhiani, V. I., Hazeltine, R. D., & Mahajan, S. M.\ 2004 Phys. Rev. E, 69, 056406

    work page 2004

  4. [4]

    I., Mahajan, S

    Berezhiani, V. I., Mahajan, S. M. & Yoshida, Z.\ 2008, Phys. Rev. E, 78, 066403

    work page 2008

  5. [5]

    Bhattacharya, D., & van den Heuvel, E. P. J. \ 1991, PhR, 203, 1

    work page 1991

  6. [6]

    \ 1995, , 446, 741

    Brandenburg, A., Nordlund, A., Stein, R., & Torkelsson, U. \ 1995, , 446, 741

    work page 1995

  7. [7]

    E., & Tchekhovskoy, A

    Broderick, A. E., & Tchekhovskoy, A. \ 2015, , 809, 97

    work page 2015

  8. [8]

    Chen, A. Y. & Beloborodov, A. M.\ 2014 , 795, L22

    work page 2014

  9. [9]

    A., Parfrey, K

    Cerutti, B., Philippov, A. A., Parfrey, K. & Spitkovsky, A.\ 2015, , 448, 606

    work page 2015

  10. [10]

    A., & Spitkovsky, A.\ 2016, , 457, 2401

    Cerutti, B., Philippov, A. A., & Spitkovsky, A.\ 2016, , 457, 2401

    work page 2016

  11. [11]

    S., & Brehme, R

    DeWitt, B. S., & Brehme, R. W. 1960, Annals of Physics, 9, 220

    work page 1960

  12. [12]

    C., & Thompson, C

    Duncan, R. C., & Thompson, C. \ 1992, , 392, L9

    work page 1992

  13. [13]

    P., et al.\ 2013, Nature (London), 501, 391

    Eatough R. P., et al.\ 2013, Nature (London), 501, 391

    work page 2013

  14. [14]

    C., et al.\ 1994, , 435, L27

    Ford, H. C., et al.\ 1994, , 435, L27

    work page 1994

  15. [15]

    F., Gammie, C

    Hawley, J. F., Gammie, C. F., & Balbus, S. A. \ 1996, , 464, 690

    work page 1996

  16. [16]

    \ 2016, , 818, 50

    Hirotani, K., & Pu, H.-Y. \ 2016, , 818, 50

    work page 2016

  17. [17]

    \ 1968, Annals of Physics, 47, 141

    Hobbs, J. \ 1968, Annals of Physics, 47, 141

    work page 1968

  18. [18]

    Koide, S.\ 2009, , 696, 2220

    work page 2009

  19. [19]

    \ 2010, , 708, 1459

    Koide, S. \ 2010, , 708, 1459

    work page 2010

  20. [20]

    D., & Lifshitz, E

    Landau, L. D., & Lifshitz, E. M.\ The Classical Theory of Fields (Elsevier, Oxford, 1975)

    work page 1975

  21. [21]

    \ 2018, , 868, 135

    Liu, W., Bian, W., Zhao, B., Yu, L., & Wang, C. \ 2018, , 868, 135

    work page 2018

  22. [22]

    \ 1992, Acta Astron., 42, 145

    Paczy \'n ski, B. \ 1992, Acta Astron., 42, 145

    work page 1992

  23. [23]

    \ 2017, , 851, L34

    Parfrey, K., & Tchekhovskoy, A. \ 2017, , 851, L34

    work page 2017

  24. [24]

    A., Cerutti, B., Tchekhovskoy, A., & Spitkovsky, A.\ 2015, , 815, L19

    Philippov, A. A., Cerutti, B., Tchekhovskoy, A., & Spitkovsky, A.\ 2015, , 815, L19

    work page 2015

  25. [25]

    A., & Spitkovsky, A.\ 2014, , 785, L33

    Philippov, A. A., & Spitkovsky, A.\ 2014, , 785, L33

    work page 2014

  26. [26]

    A., Spitkovsky, A., & Cerutti, B.\ 2015, , 801, L19

    Philippov, A. A., Spitkovsky, A., & Cerutti, B.\ 2015, , 801, L19

    work page 2015

  27. [27]

    Black Hole Gravitohydromagnetics (Springer-Verlag, Berlin, 2001)

    Punsly, B. Black Hole Gravitohydromagnetics (Springer-Verlag, Berlin, 2001)

    work page 2001

  28. [28]

    \ 1991, , 372, 424

    Punsly, B. \ 1991, , 372, 424

    work page 1991

  29. [29]

    The inner engine of GeV-radiation-emitting gamma-ray bursts

    Ruffini, R., et al. \ 2018, arxiv:1811.01839

    work page internal anchor Pith review Pith/arXiv arXiv 2018

  30. [30]

    A., Galtsov, D

    Sokolov, A. A., Galtsov, D. V., & Petukhov, V. I. 1978, Physics Letters A, 68, 1

    work page 1978

  31. [31]

    A., Ternov, I

    Sokolov, A. A., Ternov, I. M., Aliev, A. N., & Galtsov, D. V. 1983, Soviet Physics Journal, 26, 36

    work page 1983

  32. [32]

    C., East, W

    Stephens, B. C., East, W. E., & Pretorius, F. \ 2011, , 737, L5

    work page 2011

  33. [33]

    Tam, K. K. & Kiang, D.\ 1979 Prog. Theor. Phys. 62, 1245

    work page 1979

  34. [34]

    Tamburini, M., Pegoraro, F., Di Piazza, A., Keitel, C. H. & Macchi, A.\ 2010, New Journal of Physics, 12, 123005

    work page 2010

  35. [35]

    Tursunov, A., Kolo s , M., Stuchl \' k, Z., & Galtsov, D. V. \ 2018, , 861, 2

    work page 2018

  36. [36]

    Thompson, C., & Duncan, R. C. \ 1995, , 275, 255

    work page 1995

  37. [37]

    Thompson, C., & Duncan, R. C. \ 1996, , 473, 322

    work page 1996

  38. [38]

    Usov, V. V. \ 1992, Nature, 357, 472

    work page 1992

  39. [39]

    Vasisht, G., & Gotthelf, E. V. \ 1997, , 486, L129

    work page 1997

  40. [40]

    W., & Keitel, C

    Walser, M. W., & Keitel, C. H. \ 2001, LMaPh, 55, 63

    work page 2001