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.
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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
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
- 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.
The abstract, sentence by sentence
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
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| 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 was examined, and what was not
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References
How later papers used it
589 later papers cite it
21 later papers by other authors are listed below: 21 used its method or tool.
Uses its method or tool 21 of 284 papers with this label
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Used the prescription first set out in this paper to compute two-point retarded Green's functions and the electrical conductivity via Kubo's formula.
Transport Coefficients of Black MQGP M3-Branes (2014) · 1.00 · paraphrased: the licence does not allow quoting
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Used the holographic recipe for calculating retarded Green's functions from this paper with the Green-Kubo formula to find the shear viscosity to entropy ratio.
The shear viscosity of the non-commutative plasma (2007) · 1.00 · paraphrased: the licence does not allow quoting
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Applied the real-time recipe of this paper to obtain the retarded Green's function.
Transport Coefficients at Zero Temperature from Extremal Black Holes (2009) · 1.00 · paraphrased: the licence does not allow quoting
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Followed the prescription of this paper for calculating the shear viscosity.
Hydrodynamics of N=6 Superconformal Chern-Simons Theories at Strong Coupling (2008) · 1.00 · paraphrased: the licence does not allow quoting
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We bring the on-shell gravity action into the following form S^on-shell_reg = V_2∫dω/2πϕ^(0)_ωF(ω,u)|_u=ϵ^u=1ϕ^(0)_ω,and then according to the recipe [ref] , the retarded Green's function is G_R(ω) = -2lim_ϵ→0F(ω,ϵ),In the following, we compute the action terms up quadratic terms in perturbations.
Holographic Hydrodynamics of {\it Tilted} Dirac Materials (2022) · Holographic retarded Green's function and reduced $η/s$ · 1.00
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Used the gauge/gravity dual prescription of this paper for calculating Green functions in Minkowski spacetime.
Isospin diffusion in thermal AdS/CFT with flavor (2007) · 1.00 · paraphrased: the licence does not allow quoting
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Used this paper for the Green's function, expanding near z=0.
Spatial scalar correlator in strongly coupled hot N=4 Yang-Mills theory (2010) · 1.00 · paraphrased: the licence does not allow quoting
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Used the prescription in this paper to obtain the retarded Green's function for the holographic system and evaluate the sum rule integration.
Sum rules, plasma frequencies and Hall phenomenology in holographic plasmas (2010) · 1.00 · paraphrased: the licence does not allow quoting
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Extracted the Minkowski correlator of this paper from the boundary action using the procedure explained.
Negative Refraction and Superconductivity (2011) · 1.00 · paraphrased: the licence does not allow quoting
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We hence showed that we can systematically find the charge of the scalar field in the NH region and then employ the retarded Green's function method by [ref] in order to determine the QNM frequencies.
Bosonic und Fermionic Quasinormal Modes of Rotating Black Holes Through AdS/CFT (2022) · Kerr-Solution · 1.00
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Followed the prescription of this paper to calculate the glueball retarded Green's function.
Black-hole quasinormal modes and scalar glueballs in a finite-temperature AdS/QCD model (2009) · 1.00 · paraphrased: the licence does not allow quoting
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Computed real time correlators following the recipe of this paper in the Schwarzschild-like patch of the black hole.
Real time response on dS_3: the Topological AdS Black Hole and the Bubble (2009) · 1.00 · paraphrased: the licence does not allow quoting
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Followed this paper for the prescription to calculate Minkowskian correlators in AdS/CFT correspondence.
On Aspects of Holographic Thermal QCD at Finite Coupling (2015) · 1.00 · paraphrased: the licence does not allow quoting
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Applied the Minkowski AdS/CFT prescription of this paper to compute the correlation function.
Relaxation time of a CFT plasma at finite coupling (2008) · 1.00 · paraphrased: the licence does not allow quoting
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Used the prescription of this paper for obtaining the retarded Green function to arrive at the two-point retarded Green function of the U(1) baryon charge current.
Hydrodynamics and transport coefficients in an infrared-deformed soft-wall AdS/QCD model at finite temperature (2013) · 0.99 · paraphrased: the licence does not allow quoting
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Applied the Lorentzian AdS/CFT prescription of this paper to obtain the transverse component needed for the photoemission rate computation.
Plasma photoemission from string theory (2012) · 0.95 · paraphrased: the licence does not allow quoting
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Used the expansion coefficients of the retarded correlators of this paper in spatial momentum to determine the refractive index.
Refractive index in generalized superconductors with Born-Infeld electrodynamics (2018) · 0.94 · paraphrased: the licence does not allow quoting
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From this connection formulae we read out the source and the response function for the bulk field and using the holographic prescription [ref] we obtain the retarded Green's function for the scalar primary operators in the 4-dimensional thermal $CFT$.
Exact thermal correlators of holographic $CFT$s (2022) · Conclusion · 0.98
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Used the usual AdS/CFT prescription of this paper, evaluating at the asymptotic boundary with infalling boundary conditions at the horizon, to find the retarded Green's function.
Transport Properties of Holographic Defects (2008) · 0.99 · paraphrased: the licence does not allow quoting
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Used the correct prescription of this paper for computing the retarded polarization tensor.
Light-like mesons and deep inelastic scattering in finite-temperature AdS/CFT with flavor (2009) · 0.95 · paraphrased: the licence does not allow quoting
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Regarded the ratio of the response to the source as the retarded Green's function of this paper, imposing ingoing boundary conditions on the horizon.
Holographic Thermal Correlators for Hyperbolic $CFT$s (2023) · 0.89 · paraphrased: the licence does not allow quoting
How the literature uses it
561 arXiv papers cite this in 1,079 sentences
Papers citing it · 516 sentences without a confident label
Contests it 2 papers
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In fact since both $g(r_+)$ and $h_t x_1(r_+)$ vanish there is only a contribution from the horizon from the last term, but this vanishes after integrating over all $ω$ (this is in contrast to statements made in [ref] ).
Conformal field theories in $d=4$ with a helical twist · Derivatives of the on-shell action and the relationship to the Green's function · contest 0.88
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The original prescription of [ref] correctly but a-priori unjustifiably ignores the horizon contribution to the on-shell action.
All order effective action for charge diffusion from Schwinger-Keldysh holography · Son-Starinets prescription for retarded correlators revisited · contest 0.75
Builds on it 2 papers
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The usual prescription proposed in [ref] to obtain the Green's function is generalized in the present setup as follows.
Holographic Operator Mixing and Quasinormal Modes on the Brane · Holographic Green's functions · 0.93
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Finally, a generalization of the prescription of [ref] to the case of multiple fluctuation fields results in the above formula for the retarded Green function.
S-Wave Superconductivity in Anisotropic Holographic Insulators · Holographic Renormalization and Operator Mixing · 0.96
Uses its method or tool 273 papers
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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
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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
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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
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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
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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
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Our quadratic influence functional results computed using a natural extension of the recently proposed holographic SK prescription of [ref] match with the long known results of [ref] under following coordinate transformations and redefinition of parameters
Open effective theory of scalar field in rotating plasma · Quadratic effective theory · 0.98
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This result agrees with [ref] and obeys the KSS bound [ref] .
Transport Coefficients for Holographic Hydrodynamics at Finite Energy Scale · Scalar Mode and Shear Viscosity · 0.93
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It clearly shows that the timelike extra dimension can effect the two-points correlation functions both in massless and massive fields when comparing with the normal Minkowski space [ref] .
New asymptotic Anti-de Sitter solution with a timelike extra dimension in 5D relativity · two-points correlation functions · 1.00
Cites it as support 3 papers
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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
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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
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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
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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
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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
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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
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