REVIEW
Worldline formalism in a gravitational background
High Energy Physics - Theory · Submitted 17 May 2002 · 20 references
Pith's verdict: A competent method paper: worldline DR plus the -R/8 counterterm and PBC zero-mode factorization make the formalism work for external gravity, though the transverse form factors rest on an unreported Feynman-diagram comparison.
T0 · AI review
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Referee report
The paper
The paper claims
The paper argues that a scalar particle's worldline path integral, once its ultraviolet behavior is regularized covariantly, reproduces the standard one-loop graviton tadpole and self-energy and passes the general-coordinate Ward identity.
The reading
What carries the argument
The machinery is a regulated nonlinear $\sigma$ model on a circle. The covariant path-integral measure is represented by bosonic and fermionic ghosts, the constant zero mode is split off as $x^V_{DR}(V_{DR})=x_0^V_{DR}+y^V_{DR}(V_{DR})$, and the remaining periodic propagators are translationally invariant. Worldline dimensional regularization supplies the finite counterterm $V_{DR}=-R/8$, while the ghost contributions cancel the worst quantum-mechanical divergences. The load-bearing calculational step is the reduction of the self-energy to five worldline integrals $I_1,I_2,I_3,I_4,I_5$, whose values are then fed into the transverse tensor basis $S_1,S_2$ to verify the Ward identity.
Extended reading notes
Core claim
The central claim is that a scalar particle's worldline path integral in an external metric, regularized by worldline dimensional regularization with the counterterm $V_{DR}=-R/8$, yields the same one-loop graviton tadpole and self-energy as ordinary Feynman diagrams. The tadpole comes out as $V_{DR}=-R/8$ contributing to $V_{DR}$, and the two-point function is written in a compact form whose tensor structures $S_1$ and $S_2$ are transverse, so that the Ward identity in eq. (40) holds for any $V_{DR}$. The authors present this as evidence that the worldline method is a practical first-quantized computational scheme for external gravity, not just for flat-space or gauge backgrounds.
Load-bearing premise
The load-bearing premise is that the dimensional-regularization recipe used here — extend the worldline by $d$ infinite dimensions, integrate by parts, then send $dV_{DR}$ whenever no ambiguity remains — really leaves no ambiguity in the five self-energy integrals, so that the quoted finite parts and the Ward-identity check are meaningful.
Original abstract
We analyze the worldline formalism in the presence of a gravitational background. In the worldline formalism a path integral is used to quantize the worldline coordinates of the particles. Contrary to the simpler cases of scalar and vector backgrounds, external gravity requires a precise definition of the ultraviolet regularization of the path integral. Taking into account the UV regularization, we describe the first quantized representation of the one-loop effective action for a scalar particle. We compute explicitly the contribution to the graviton tadpole and self-energy to test the validity of the method. The results obtained by usual field theoretical Feynman diagrams are reproduced in an efficient way. Finally, we comment on the technical problems related to the factorization of the zero mode from the path integral on the circle.
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
We analyze the worldline formalism in the presence of a gravitational background. In the worldline formalism a path integral is used to quantize the worldline coordinates of the particles. Contrary to the simpler cases of scalar and vector backgrounds, external gravity requires a precise definition of the ultraviolet regularization of the path integral. Taking into account the UV regularization, we describe the first quantized representation of the one-loop effective action for a scalar particle. We compute explicitly the contribution to the graviton tadpole and self-energy to test the validity of the method. The results obtained by usual field theoretical Feynman diagrams are reproduced in an efficient way. Finally, we comment on the technical problems related to the factorization of the zero mode from the path integral on the circle.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We analyze the worldline formalism in the presence of a gravitational background. | contribution 0.88 | 0.89 | 0.05 | asserted 0.92 |
| s1 | In the worldline formalism a path integral is used to quantize the worldline coordinates of the particles. | background 0.89 | 0.08 | 0.03 | asserted 1.00 |
| s2 | Contrary to the simpler cases of scalar and vector backgrounds, external gravity requires a precise definition of the ultraviolet regularization of the path integral. | background 0.76 | 0.15 | 0.07 | asserted 1.00 |
| s3 | Taking into account the UV regularization, we describe the first quantized representation of the one-loop effective action for a scalar particle. | contribution 0.74 | 0.93 | 0.11 | asserted 1.00 |
| s4 | We compute explicitly the contribution to the graviton tadpole and self-energy to test the validity of the method. | contribution 0.74 | 0.96 | 0.12 | asserted 0.97 |
| s5 | The results obtained by usual field theoretical Feynman diagrams are reproduced in an efficient way. | result 0.87 | 0.88 | 0.54 | asserted 1.00 |
| s6 | Finally, we comment on the technical problems related to the factorization of the zero mode from the path integral on the circle. | limitation 0.70 | 0.56 | 0.04 | unclear 0.78 |
What was examined, and what was not
- arXiv listing abstract v2
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Figures
Figures reproduced from arXiv:hep-th/0205182 by the authors.
References
How the literature uses it
35 arXiv papers cite this in 40 sentences
Papers citing it · 22 sentences without a confident label
Builds on it 1 paper
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We have thus extended the gauge-theory result of [ref] , by showing that also in gravitational theories there is a clear connection between the worldline representation of an asymptotic dressed propagator and the more studied worldline quantization on the circle (i.e. the one-loop effective action), which by definition is constructed with denominators only (see e.g. [ref] ).
Generalized Wilson lines and the gravitational scattering of spinning bodies · A trick with conserved charges and the asymptotic limit · 0.93
Uses its method or tool 4 papers
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([ref]) in terms of its worldline-representation [ref]
The Relation Between KMOC and Worldline Formalisms for Classical Gravity · From KMOC to worldline observables · 0.97
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First, we employ a Euclidean worldline (proper-time) representation [ref] , which makes the winding interpretation manifest and directly exhibits the exponential suppression arising from the worldline-instanton action in warped space.
Axion Quality in Warped Extra-Dimension · Axion potential in the absence of fixed-point localized operators · 1.00
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In the sigma model we deal with the corresponding zero mode in the “string inspired” way by imposing [ref] [equation] This yields a translationally invariant formalism on the world-line that allows us to fix $τ_1=0$.
Causality and Micro-Causality in Curved Spacetime · The World-Line Sigma Model, Penrose Limit and Null Congruences · 0.97
Cites it as background 12 papers
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Among the several techniques to evaluate functional determinants, the versatile worldline formalism [ref] has proved adaptable to different types of fields on curved spacetimes: scalars [ref] , spinors [ref] (see also [ref] ), and vectors [ref] (where, more generally, antisymmetric tensor fields of arbitrary rank are considered) have been studied with worldline techniques.
Worldline Images for Yang-Mills Theory within Boundaries · Introduction · 0.81
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The emission or absorption of quanta, such as photons [ref] , gluons [ref] or gravitons [ref] , is described by inserting suitable vertex operators along the line, in a way that closely resembles string perturbation theory.
Worldline geometries for scattering amplitudes · Introduction · 0.87
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Worldline methods have a long-standing history in the study of quantum field theories, see [ref] for a review and [ref] for the inclusion of gravitational backgrounds.
Worldline path integrals for the graviton · Introduction · 1.00
Discussion
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