REVIEW
An axiomatic approach to electromagnetic and gravitational radiation reaction of particles in curved spacetime
General Relativity and Quantum Cosmology · Submitted 24 Oct 1996 · 18 references
Pith's verdict: The method is the contribution, not the equations — and the gravitational cross-check against Mino et al. is weaker than it's usually given credit for.
T0 · AI review
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Referee report
The paper
The paper claims
Two axioms are enough to pin down the radiation-reaction force on a small charged or massive body in curved spacetime, reproducing the known electromagnetic result and yielding a gravitational equation of motion whose only departure from a
The reading
What carries the argument
The load-bearing device is the comparison axiom. It converts an ill-posed point-particle limit into a statement about differences: if two bodies have accelerations of equal magnitude, the singular parts of their self-fields cancel under a Riemann-normal-coordinate identification that aligns $u^a$ and $a^a$, so the residual force is the ordinary Lorentz force (or its gravitational analogue $-C_{abc}u^bu^c$) of the field difference, averaged over a sphere of geodesic radius $r$ and taken as $r → 0$. The averaging sphere is what makes the answer finite and unambiguous. Feeding this with the Hadamard expansion of the retarded field near the world line — whose divergent terms depend only on $u^a$ and $a^a$, not on curvature or $ȧ^a$ — produces the explicit force formulas without any computation of the electromagnetic or gravitational stress-energy near the world line. Reduction of order, treating $e^2/m$ (or $m$) as a small parameter and substituting back the differentiated equation, then removes the runaway solutions.
Extended reading notes
Core claim
The paper's central claim is that the leading self-force on a small body in curved spacetime is fixed by a comparison axiom rather than by a detailed model of the body. In the electromagnetic case the axiom plus the flat-spacetime vanishing condition yields $f^a_{EM} = e(F^{in})^{ab}u_b + (2/3)e^2(ȧ^a - a^2u^a) + (1/3)e^2(R^a{}_bu^b + u^aR_{bc}u^bu^c) + e^2u^b∫^{τ^-}_{-∞}∇_{[b}(G^-)^{a]}{}_{c'}u^{c'}(τ')dτ'$, which agrees with DeWitt and Brehme as corrected by Hobbs. In the gravitational case the analogous axioms give a force containing a term parallel to the four-velocity (which only renormalises how $u^a$ is normalised) and, after projection and reduction of order, the equation of motion $a^a = (½∇^aγ^{in}_{bc} - ∇_b(γ^{in})_c{}^a - ½u^au^d∇_dγ^{in}_{bc})u^bu^c + mu^bu^c∫^{τ^-}_{-∞}(½∇^aG^-{}_{bc}{}^{a'b'} - ∇_b(G^-)_c{}^{aa'b'} - ½u^au^d∇_dG^-{}_{bc}{}^{a'b'})u_{a'}u_{b'}dτ'$. Because the paper works only to linear order in both $m$ and the incoming perturbation $γ^{in}_{ab}$, the Abraham-Lorentz-type terms $(ȧ^a - a^2u^a)$ cannot be retained consistently, and the tail integral survives as the sole self-force contribution.
Load-bearing premise
The comparison axiom itself: that when two particles have accelerations of equal magnitude, the difference in their self-forces is exactly the averaged ordinary force of the difference of their fields, because the volume integral of the field difference vanishes as both bodies shrink. The authors argue this only by plausibility, from the structure of the extended-body force integral, and state in the Conclusions that they did not prove the axioms follow from Maxwell's equations or from Einstein's equation.
Editorial extensions
If this is right
- The electromagnetic self-force formula of DeWitt and Brehme, as corrected by Hobbs, follows from two postulates plus the Hadamard expansion, without computing the singular stress-energy tensor near the world line.
- For a small body in vacuum, the leading correction to geodesic motion at order $m$ is a nonlocal tail integral over the past world line, so the equation of motion is integro-differential rather than local.
- The local acceleration and jerk terms that appear at intermediate stages do not survive the reduction of order at linear order in $m$, so any local 'Abraham-Lorentz' contribution in the gravitational case is an artefact of truncation.
- The result is stated to agree with the independent calculation of Mino, Sasaki and Tanaka, giving two routes to the same equation of motion.
- In the slow-motion, weak-field limit the tail term is expected to become effectively local, mimicking the standard Abraham-Lorentz (electromagnetic) and quadrupole-derived (gravitational) damping forces.
Reading between the lines
- If the comparison axiom is correct, it should generalise beyond Maxwell and linearised gravity: any linear field equation with a distributional point source whose Hadamard expansion has velocity-and-acceleration-only divergences would admit the same difference-of-forces construction.
- The paper's own framing suggests a clean numerical test: compute the self-force for two small extended bodies of equal acceleration magnitude but different internal structure, and check whether their force difference converges to the averaged field-difference Lorentz force as the bodies shrink.
- Because the tail integral is the sole surviving gravitational term at linear order, the practical content of the result for astrophysical inspirals is a statement about how much of the past orbit must be retained; the size of the effective memory of the tail is the natural quantity to quantify next.
- The authors note that they did not derive the axioms from the field equations; a derivation would likely proceed by controlling the volume integral in their equation (16) uniformly over a one-parameter family of extended bodies, which is exactly where they say the main obstacle lies.
Original abstract
The problem of determining the electromagnetic and gravitational ``self-force'' on a particle in a curved spacetime is investigated using an axiomatic approach. In the electromagnetic case, our key postulate is a ``comparison axiom'', which states that whenever two particles of the same charge $e$ have the same magnitude of acceleration, the difference in their self-force is given by the ordinary Lorentz force of the difference in their (suitably compared) electromagnetic fields. We thereby derive an expression for the electromagnetic self-force which agrees with that of DeWitt and Brehme as corrected by Hobbs. Despite several important differences, our analysis of the gravitational self-force proceeds in close parallel with the electromagnetic case. In the gravitational case, our final expression for the (reduced order) equations of motion shows that the deviation from geodesic motion arises entirely from a ``tail term'', in agreement with recent results of Mino et al. Throughout the paper, we take the view that ``point particles'' do not make sense as fundamental objects, but that ``point particle equations of motion'' do make sense as means of encoding information about the motion of an extended body in the limit where not only the size but also the charge and mass of the body go to zero at a suitable rate. Plausibility arguments for the validity of our comparison axiom are given by considering the limiting behavior of the self-force on extended bodies.
The compiled record
The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.
The abstract, sentence by sentence
The problem of determining the electromagnetic and gravitational ``self-force'' on a particle in a curved spacetime is investigated using an axiomatic approach. In the electromagnetic case, our key postulate is a ``comparison axiom'', which states that whenever two particles of the same charge $e$ have the same magnitude of acceleration, the difference in their self-force is given by the ordinary Lorentz force of the difference in their (suitably compared) electromagnetic fields. We thereby derive an expression for the electromagnetic self-force which agrees with that of DeWitt and Brehme as corrected by Hobbs. Despite several important differences, our analysis of the gravitational self-force proceeds in close parallel with the electromagnetic case. In the gravitational case, our final expression for the (reduced order) equations of motion shows that the deviation from geodesic motion arises entirely from a ``tail term'', in agreement with recent results of Mino et al. Throughout the paper, we take the view that ``point particles'' do not make sense as fundamental objects, but that ``point particle equations of motion'' do make sense as means of encoding information about the motion of an extended body in the limit where not only the size but also the charge and mass of the body go to zero at a suitable rate. Plausibility arguments for the validity of our comparison axiom are given by considering the limiting behavior of the self-force on extended bodies.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | The problem of determining the electromagnetic and gravitational ``self-force'' on a particle in a curved spacetime is investigated using an axiomatic approach. | contribution 0.78 | 0.84 | 0.07 | asserted 0.92 |
| s1 | In the electromagnetic case, our key postulate is a ``comparison axiom'', which states that whenever two particles of the same charge $e$ have the same magnitude of acceleration, the difference in their self-force is given by the ordinary Lorentz force of the difference in their (suitably compared) electromagnetic fields. | method 0.83 | 0.68 | 0.08 | asserted 0.99 |
| s2 | We thereby derive an expression for the electromagnetic self-force which agrees with that of DeWitt and Brehme as corrected by Hobbs. | result 1.00 | 0.92 | 0.16 | asserted 1.00 |
| s3 | Despite several important differences, our analysis of the gravitational self-force proceeds in close parallel with the electromagnetic case. | method 0.77 | 0.84 | 0.05 | asserted 1.00 |
| s4 | In the gravitational case, our final expression for the (reduced order) equations of motion shows that the deviation from geodesic motion arises entirely from a ``tail term'', in agreement with recent results of Mino et al. Throughout the paper, we take the view that ``point particles'' do not make sense as fundamental objects, but that ``point particle equations of motion'' do make sense as means of encoding information about the motion of an extended body in the limit where not only the size but also the charge and mass of the body go to zero at a suitable rate. | result 0.91 | 0.87 | 0.40 | asserted 0.99 |
| s5 | Plausibility arguments for the validity of our comparison axiom are given by considering the limiting behavior of the self-force on extended bodies. | method 0.57 | 0.79 | 0.05 | hedged possibility 0.72 |
What was examined, and what was not
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References
How later papers used it
146 later papers cite it
1 later paper by other authors is listed below: 1 used its method or tool.
Uses its method or tool 1 of 7 papers with this label
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Used the Quinn-Wald prescription, subtracting the singular field from the retarded field near the particle, averaging over a surrounding sphere, and taking the limit as its radius shrinks to zero.
Gravitational Self-force in a Radiation Gauge (2010) · 0.91 · paraphrased: the licence does not allow quoting
How the literature uses it
120 arXiv papers cite this in 166 sentences
Papers citing it · 75 sentences without a confident label
Uses its method or tool 6 papers
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These formulas were recently developed in [ref] , building on earlier related discussions found in [ref] .
Circular orbits and polarized images of charged particles orbiting Kerr black hole with a weak magnetic field · Introduction · 0.93
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Adiabatic waveforms from inspiral trajectories.—We now turn to adiabatic waveforms from orbits that slowly inspiral due to first-order [$O(η)$] GSF effects [ref] , specifically following the two-timescale framework developed in Refs. [ref] .
Adiabatic waveforms from extreme-mass-ratio inspirals: an analytical approach · Introduction · 0.92
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Following [ref] , they suggest the finite subtraction be carried out via [equation] where $$ indicates a different spacetime, $r=(σ_b u^b)_τ_+$ and the angular brackets are introduced to average out any directional dependence.
Regularization of a scalar charged particle for generic orbits in Kerr spacetime · The Quinn-Wald regularization procedure · 0.97
Cites it as background 75 papers
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The solution for a massive point-particle moving in a strong field and for any velocity was indeed derived in 1997 by Mino, Sasaki and Tanaka [ref] , Quinn and Wald [ref] , in the de Donder [ref] (harmonic) gauge[The harmonic gauge was also proposed by Lanczos [ref] ], around an expansion of the mass ratio, $m/M$, $m$ being the small mass and $M$ the large one.
Self-force driven motion in curved spacetimes · The two-body problem and the perturbation method · 0.90
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The first correct expression for a regularised self-force in the case of a scalar charge was produced by Quinn [ref] , which used the same regularization procedure developed by Quinn and Wald [ref] , often referred to as the axiomatic approach.
Regularization of a scalar charged particle for generic orbits in Kerr spacetime · The Quinn-Wald regularization procedure · 0.86
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A formal expression for the gravitational self-force was first derived in 1996 by Mino, Sasaki, and Tanaka [ref] and Quinn and Wald [ref] ; the resulting equation of motion is now known as the MiSaTaQuWa equation.
The self-consistent gravitational self-force · Introduction · 0.96
Discussion
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