Pith. Sign in

REVIEW

Minkowski-space correlators in AdS/CFT correspondence: recipe and applications

High Energy Physics - Theory · Submitted 7 May 2002 · 45 references

Pith's verdict: The paper that gave everyone a working recipe for real-time AdS/CFT; the derivation gap is real but the checks are honest and the conjecture is narrower than it looks.

T0 · AI review

How this review was made: An AI referee (selfhosted/deepseek-v4.1-flash) read the paper on October 29, 2026 and answered a fixed list of questions about it. T0 is the starting level every paper gets. The levels describe how deeply Pith has checked the paper, never the authors.

  1. T0 AI review An AI read the paper and answered a fixed list of questions.
  2. T1 Audit Automatic checks that the references and files the paper relies on exist and match.
  3. T2 Compute The paper's code or calculations re-run with the same results.
  4. T3 Formal statement The claims written out in a formal math language a computer can read.
  5. T4 Proof Those claims proved, and the proof checked by computer.

How Pith checks papers →

· 3 major objections · 6 minor · Ask about this paper · The compiled record · Read the full review →
Challenge this review Comment (0) Read on arXiv ↗
Cite ▾
arXiv IDhep-th/0205051 (version 2)
Pith IDIQKJ2QYV, Pith's permanent record of this paper and its review
CitationA.O.Starinets, D.T.Son. "Minkowski-space correlators in AdS/CFT correspondence: recipe and applications." arXiv:hep-th/0205051 (2002). https://pith.science/paper/IQKJ2QYV
Cite this reviewBibTeX for Pith's review of this paper
Claim paper

Why Pith says this

Highlight any text to comment on it.

Referee report
The paper

The paper claims

A working recipe lets physicists compute real-time quantum correlators directly from a black hole's gravity dual, with the horizon's ingoing-wave condition standing in for the choice of retarded propagator.

The reading

Quantum field theories at finite temperature have several different real-time correlation functions — retarded, advanced, Feynman — and only the retarded one tells you how a system responds to a small push and how quickly it returns to equilibrium. The standard AdS/CFT dictionary was built in Euclidean signature, where there is only one correlator and analytic continuation back to real time requires knowing the answer at every Matsubara frequency, which gravity calculations almost never deliver. This paper proposes a direct Lorentzian recipe: solve the bulk wave equation for a field whose boundary value is fixed to one and which, at the horizon, is a purely ingoing wave; then read the retarded Green's function off the boundary term of the on-shell action, discarding the horizon term. The authors check the recipe against two cases where the answer is independently known — a massless scalar in pure anti-de Sitter space and the two-dimensional conformal theory dual to the BTZ black hole — and then apply it to predict a strong-coupling value for the Chern-Simons diffusion rate of hot $N=4$ super Yang-Mills.

What carries the argument

The load-bearing object is the boundary flux function $F(k,z) = K√{-g}g^{zz}f_{-k}(z)∂_zf_k(z)$, evaluated at the boundary only. Its imaginary part is radially conserved, so it can be computed at the horizon as a shortcut, but its real part at the boundary is what carries the correlator. The second piece of machinery is the horizon boundary condition: for timelike momenta the solution must be a purely ingoing wave (an outgoing wave for the advanced propagator), and for spacelike momenta it must be regular. The third piece is the observation that the normalisation coefficient $A(k)$ multiplying the non-normalisable branch vanishes precisely when the Dirichlet condition defining a quasinormal mode is imposed, which is why quasinormal frequencies appear as poles of $G_R$.

Extended reading notes

Core claim

The central claim is a prescription, not a theorem: for a bulk field $f_k(z)$ normalised to $1$ at the boundary and satisfying an ingoing-wave condition at the horizon, the retarded Green's function of the dual boundary operator is $G_R(k) = -2F(k,z)$ evaluated at the boundary, with $F(k,z) = K$ times $f_{-k}(z)$ times $f_k'(z)$ times the appropriate metric factor. The authors first explain why the naive Lorentzian version of the dictionary fails: differentiating the on-shell action gives a quantity whose imaginary part is a conserved flux, so the horizon contribution exactly cancels the boundary contribution and the result is real, whereas a retarded propagator must be complex. Their fix is to keep only the boundary term and to let the ingoing-wave condition at the horizon encode which real-time propagator is being computed. They verify the recipe at zero temperature, recovering $G_R(k) = N^2k^4/(64π^2)(ln|k^2| - iπθ(-k^2)sgn ω)$ for the operator dual to a massless scalar, and at finite temperature in the BTZ background, where the gravity result for the retarded correlator matches the analytic continuation of the known two-dimensional conformal field theory correlator. As an application they obtain a Chern-Simons diffusion rate $Γ = (g^2_{YM}N)^2 T^4/(256π^3)$ at large 't Hooft coupling, and they show that the poles of the retarded correlator are exactly the quasinormal frequencies of the black hole.

Load-bearing premise

The recipe assumes that discarding the horizon term of the on-shell action and keeping only the boundary term, combined with the ingoing-wave condition at the horizon, yields the retarded Green's function — a step the authors themselves say does not follow from any identity of the usual generating-functional form and justify only by the cases where an independent check exists.

Editorial extensions

If this is right

  • Real-time transport coefficients of strongly coupled gauge theories become computable from gravity without any Euclidean analytic continuation, starting with the Chern-Simons diffusion rate $Γ = (g^2_{YM}N)^2T^4/(256π^3)$.
  • The same machinery, applied to the graviton and to R-charge perturbations, yields the shear viscosity and charge diffusion rate of the thermal plasma, which the authors pursue in a companion paper.
  • The poles of the retarded Green's function coincide with black-hole quasinormal frequencies, giving a quantitative gravity-side account of how fast a perturbed strongly coupled plasma returns to thermal equilibrium.
  • The imaginary part of the correlator for spacelike momenta at high momentum is exponentially suppressed by a Boltzmann-like factor with a coefficient near $0.835$, which the authors note is stronger suppression than a weakly coupled plasma would give.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • If the recipe holds generally, it turns the quasinormal spectrum of any asymptotically anti-de Sitter black hole into a directly readable list of poles of a boundary correlator, which suggests quasinormal-mode numerics can be repurposed as a spectral calculator for strongly coupled matter.
  • The explicit failure of the naive on-shell-action route — a real answer where a complex one is required — suggests that Lorentzian holography needs a boundary-condition-dependent state-selection rule rather than a single generating functional, a point that a fully general formulation would have to absorb.
  • The gap between the strong-coupling diffusion coefficient scaling as $(g^2_{YM}N)^2$ and the weak-coupling $ (g^2_{YM}N)^5\ln(1/g^2_{YM}N)$ invites an interpolation question: whether a single monotonic function of the 't Hooft coupling connects the two regimes, which lattice or resummation work could in principle probe.
Original abstract

We formulate a prescription for computing Minkowski-space correlators from AdS/CFT correspondence. This prescription is shown to give the correct retarded propagators at zero temperature in four dimensions, as well as at finite temperature in the two-dimensional conformal field theory dual to the BTZ black hole. Using the prescription, we calculate the Chern-Simons diffusion constant of the finite-temperature N=4 supersymmetric Yang-Mills theory in the strong coupling limit. We explain why the quasinormal frequencies of the asymptotically AdS background correspond to the poles of the retarded Green's function of the boundary conformal field theory.

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.

Compiled by classifier-1.13-20260917 via OpenRouter, question bank abstract-p1-20260923, 2026-09-23: 1 request, 3,663 input tokens, $0.0002 reported.

What the abstract itself states, as probabilities: claims first 0.04 · states limitation 0.12 · human participants 0.01 · controlled comparison 0.03 · randomized assignment 0.01 · states quantitative result 0.12 · compares with prior results 0.39 · mentions code or data availability 0.02.

The abstract, sentence by sentence

arXiv listing abstract v2. Results and the main claim are underlined; .

We formulate a prescription for computing Minkowski-space correlators from AdS/CFT correspondence. This prescription is shown to give the correct retarded propagators at zero temperature in four dimensions, as well as at finite temperature in the two-dimensional conformal field theory dual to the BTZ black hole. Using the prescription, we calculate the Chern-Simons diffusion constant of the finite-temperature N=4 supersymmetric Yang-Mills theory in the strong coupling limit. We explain why the quasinormal frequencies of the asymptotically AdS background correspond to the poles of the retarded Green's function of the boundary conformal field theory.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#sentencerolethe authors' own workstates the main conclusionstrength
s0 We formulate a prescription for computing Minkowski-space correlators from AdS/CFT correspondence. contribution 0.95 0.94 0.41 asserted 0.99
s1 This prescription is shown to give the correct retarded propagators at zero temperature in four dimensions, as well as at finite temperature in the two-dimensional conformal field theory dual to the BTZ black hole. result 0.97 0.89 0.27 asserted 1.00
s2 Using the prescription, we calculate the Chern-Simons diffusion constant of the finite-temperature N=4 supersymmetric Yang-Mills theory in the strong coupling limit. result 0.79 0.95 0.16 asserted 1.00
s3 We explain why the quasinormal frequencies of the asymptotically AdS background correspond to the poles of the retarded Green's function of the boundary conformal field theory. interpretation 0.72 0.79 0.13 asserted 0.99

What kind of paper the classifier reports this is: method or tool 0.98 · evidence from proof or derivation 0.97.

What was examined, and what was not

sources read
  • arXiv listing abstract v2
not examined
  • full text
  • figures and tables
  • references and citing sentences
  • relations to other papers
levels run
  • P abstract
not run
  • S sections
  • T body sentences
  • C citations
  • R cross-paper relations

Every quoted sentence on this record is the authors'. Every label is from Pith's closed vocabulary, with the probability shown beside it. Every number in the measurements table is the authors', checked by code. Record as JSON

References
How later papers used it

589 later papers cite it

Evidence: substantial. 576 of the citing papers share no author with it, and 290 of those carry a confident label from Pith's citation classifier.

Pith read 40 of the 1,110 citing sentences, choosing only those whose citation markers point at this paper alone, and wrote the paraphrases from them. The summary, the counts, the evidence level, the links and the quotes come from code; the summary counts the papers listed below. A later paper is listed under a label when Pith's citation classifier gives one of its sentences that label at probability 0.8 or more (0.95 for support), Pith's reading finds that the citing paper itself did it, and a second check confirms the paraphrase against the sentence. This section lists uses only. It does not list criticism or disagreement, so their absence here says nothing about how the paper has been received. Papers that share an author with this one are listed apart, under "By the same authors". A quote is the citing authors' own sentence, shown when their paper's licence is CC BY, CC BY-SA or CC0. JSON

Uses its method or tool 21 of 284 papers with this label
How the literature uses it

561 arXiv papers cite this in 1,079 sentences

Each citing sentence is taken from the citing paper's LaTeX source and typed by Pith's classifier. A label appears at probability 0.8 or more (0.95 for support), a contest at 0.7 or more; the quoted words are the citing authors'. How each label was checked · JSON

Papers citing it · 516 sentences without a confident label

Contests it 2 papers
Builds on it 2 papers
Uses its method or tool 273 papers
  • Further, we move on to the computation of two-point retarded Green's functions by using the prescription first set out in [ref] using which one can calculate the electrical conductivity by utilising Kubo's formula.

    Transport Coefficients of Black MQGP M3-Branes · Introduction · 1.00

  • Using the holographic recipe for calculating retarded Greens functions [ref] and the Green-Kubo formula [ref] we find η_1 = lim_ω→0 1/ω (-2 F(u=0)) = N^2 πT^3/8 , which leads to the universal value $η/s = 1/ 4π$ for the shear viscosity to entropy ratio.

    The shear viscosity of the non-commutative plasma · Scalar channel. · 1.00

  • The prescription for computing the retarded Green's function [ref] is that we solve the equation for our scalar field in the black hole background ([ref]) with ingoing boundary conditions at the black hole horizon $z=1$, ψ∼(1-z)^i / (h^2 +q^2-3) .

    Impure AdS/CFT · Numerical results for $1/τ_imp$ · 1.00

Uses its data or values 2 papers
  • The absorption of the axions by the black hole with a cross section equal to the area of the black hole delivers the following result [ref] : Γ= (g^2 N)^2/256 π^3 T^4 , showing that topological transitions become more frequent at strong coupling, even though the dependence on the coupling is weaker than suggested by Eq.[ref].

    Topology, magnetic field, and strongly interacting matter · Chern-Simons diffusion in non-Abelian plasma at strong coupling: holography · 0.82

  • In QCD at high temperature, the chirality flipping rate is estimated from the sphaleron rate as $Γ_sphal∼α_s^5 T^4$ [ref] , where $α_s$ is the strong coupling constant.

    Foundations and Applications of Quantum Kinetic Theory · Recursive relation and semi-classical expansion in equilibrium and constant fields · 0.86

Compares with it 17 papers
Cites it as support 3 papers
  • We thus expect $G^R_χ$ to have no singularity at $k,ω= 0$, an assertion also backed by the AdS/CFT correspondence [ref] .

    Energy and momentum dependence of the soft-axion interaction rate · Update on axion contribution to $ΔN^ _eff$ · 1.00

  • An example which motivates such a conjecture is the relation between the poles of retarded two-point functions of the dual quantum theory at the boundary, which determine the properties of return to equilibrium, and quasinormal modes of AAdS black holes [ref] .

    Structural and Dynamical Aspects of the AdS/CFT Correspondence: a Rigorous Approach · Obstructions to the inversion of Rehren duality · 0.98

  • There are many examples in QCD [ref] and holography [ref] where this is confirmed.[In those examples the operator in the correlator was the stress tensor $T$ in four dimensions rather than $ϕ$.

    Thermal CFTs in momentum space · Sum rules · 0.98

Cites it as background 104 papers
  • Having reviewed the construction in [ref] of the delocalized type IIA mirror of the type IIB background of [ref] as well its M-theory uplift, in 2.5, we will briefly review the general gauge-gravity duality techniques of [ref] of obtaining two-point functions involving energy momentum tensor/currents and summarize a host of results of [ref] obtained as a result of its application.

    On Aspects of Holographic Thermal QCD at Finite Coupling · Type IIB and M-Theory Thermodynamics · 0.88

  • The real-time formulation of holography initiated in [ref] (see also [ref] ) relates the Fourier space retarded Green's functions $G^R(ω,k)$ of boundary operators to the solutions of classical bulk equations for perturbations obeying ingoing boundary conditions at the black hole horizon.

    Horizon constraints on holographic Green's functions · Introduction · 0.93

  • In particular, thermodynamic and hydrodynamic behavior are encoded in black hole geometries and their quasi-normal modes (QNMs) [ref] .

    Holographic D-brane constructions with dynamical gauge fields · Introduction · 0.85

Discussion

Disagree with the review, or know something it missed? Leave a comment, highlight any passage above to comment on it, or challenge this review formally.