REVIEW 3 major objections 5 minor 2 cited by
Gravity in de Sitter space may make the out-of-time-ordered correlator grow, in apparent violation of the quantum bound on chaos.
Reviewed by Pith at T0; open to challenge. T0 means a machine referee read the full paper against a public rubric. the ladder, T0–T4 →
T0 review · deepseek-v4-flash
2026-08-02 06:07 UTC pith:MWQ2F6GO
load-bearing objection Technically serious and largely explicit dS OTOC computation, but the headline growth claim rests on a large-diffeomorphism contribution whose gauge-invariant status is not yet established; the authors concede the dressing question is open. the 3 major comments →
Out-of-time-ordered Correlators in de Sitter Revisited
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Using the eikonal approximation for gravitational scattering of massive scalars around de Sitter space in any dimension, the authors compute the 4-point OTOC of operators placed along an observer's worldline. They find that the perturbative OTOC initially grows: in the unregulated massless calculation, D/(G13G24) = 1 + C G_N ℓ^{-d} e^{t/ℓ} with C>0 (eq. 5.67), i.e., growth with the maximal Lyapunov exponent 2π/β_dS, driven by the L=0 angular mode; in the m_g-regulated double-scaling limit, only even powers of G_N/m_g² survive and the first correction grows as e^{4πt/β_dS} (eqs. 5.28–5.30). The authors emphasize that this growth is mediated by large diffeomorphisms in the graviton propagator—
What carries the argument
The central object is the eikonal phase, the exponent of the resummed ladder diagrams, written as an integral of the graviton propagator contracted with the null momenta of two nearly lightlike scalar trajectories. The argument hinges on the decomposition of the graviton propagator into transverse-traceless, vector, and scalar (longitudinal) parts, and specifically on the pure-diffeomorphism piece ∇µ∇ν∇µ′∇ν′ G^{−−}_{m²=−d} (eq. 4.21), a tachyon-mass regularized scalar propagator whose Z log Z growth yields the L=0 'time advance' contribution; and the L=1 vector zero mode of the transverse sphere, which causes a logarithmic IR divergence that is regularized by a graviton mass m_g. In the regu
Load-bearing premise
The load-bearing premise is that the pure-diffeomorphism part of the graviton propagator contributes physically to a gauge-invariant OTOC; the paper itself notes in §6 that it did not properly discuss the gravitational dressing of the external operators, and if that dressing cancels or renormalizes these large gauge modes—as the L=1 vector sector is canceled by constraints—the growth disappears.
What would settle it
Compute the OTOC using an explicitly gauge-invariant definition with operators dressed to an observer worldline (as the abstract promises but Section 6 admits is not done), and check whether the coefficient C in D/(G13G24) = 1 + C G_N ℓ^{-d} e^{t/ℓ} (eq. 5.67) remains positive; if dressing removes the L=0 diffeomorphism contribution, C would vanish or change sign. Alternatively, compute the same regulated eikonal phase with a different IR regulator (e.g., deforming to a conical defect in dS3) and compare the Lyapunov exponents; if the 4π/β_dS scaling is regulator-dependent, the claim is not ro
If this is right
- The gravitational OTOC in de Sitter can grow initially for any bulk scalar masses, contradicting the quantum bound on chaos in the regularized 'bound on chaos' configuration.
- In the mass-regulated double-scaling limit, all odd powers of Newton's constant vanish, so the leading correction grows with twice the maximal Lyapunov exponent, e^{4πt/β_dS}.
- The eikonal phase in de Sitter is sensitive to large diffeomorphisms and to the choice of integration contour, unlike AdS where only the physical transverse-traceless part contributes.
- The loop-level IR divergence in the vector sector cannot be removed by dressing external operators; the authors suggest deforming away from empty de Sitter (e.g., a conical defect in dS3) may be needed to resolve it.
- The initial growth is caused by time advance rather than time delay, consistent with earlier geodesic-approximation results but now derived from a first-principles diagrammatic computation.
Where Pith is reading between the lines
- If a complete gauge-invariant construction of the OTOC with observer-dressed operators cancels the large-diffeomorphism modes (as the L=1 vector mode is canceled by constraints at tree level), the predicted growth—the paper's headline—would disappear; the paper concedes in §6 that it did not properly discuss this dressing.
- The claimed violation of the bound on chaos may be an artifact of the eikonal approximation's treatment of zero modes rather than a genuine property of quantum gravity in de Sitter; a fully non-perturbative computation (e.g., in a microscopic model such as the doubled SYK model with equal-energy constraint) could test this.
- The result suggests operators in de Sitter become 'simpler' under time evolution, opposite to the usual operator-growth picture of chaos; if physical, it could indicate that de Sitter holography requires dressing that creates complicated operators.
- The gauge-dependence of the loop-phase divergence implies the mass-regulator procedure may not be unique; verifying that different regularizations (e.g., conical defect deformation) yield the same Lyapunov exponent would strengthen the claim.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper revisits the computation of four-point out-of-time-order correlators (OTOCs) in de Sitter space in the eikonal approximation. It derives the eikonal phase from resummed graviton exchange (Section 3), identifies an infrared divergence in the vector sector of the graviton propagator (Section 4.3), and computes the OTOC both with and without a graviton-mass regulator (Sections 5.3 and 5.5). The headline results are: (i) at tree level the unregulated OTOC grows as 1 + C G_N ℓ^{-d} e^{t/ℓ} with C>0 in the pole–antipole and chaos-bound configurations (eq. (5.67)), i.e. with the maximal Lyapunov exponent 2π/β_dS; and (ii) in the regulated double-scaling limit only even powers of G_N/m_g^2 survive, giving a leading correction e^{4πt/β_dS} (eqs. (5.28), (5.30)). The authors trace the tree-level growth to an L=0 large-diffeomorphism term in the graviton propagator (eq. (4.21)) and interpret the result as challenging the applicability of the MSS bound on chaos.
Significance. The computation is explicit and largely self-contained: the wavefunctions (5.19), the master formula (5.3), and the analytic continuations leading to (5.24) and (5.67) are spelled out, and the sign of the tree-level growth is traced to the negative eigenvalue of the L=0 transverse Green function (5.62). If the growth survives a fully gauge-invariant treatment, it would be a striking counterexample to the universality of the bound on chaos and would support the idea that large diffeomorphisms can be physically observable in de Sitter. However, the result hinges on an unproven assumption about observer dressing, and the loop-level/regulated claims are not backed by a direct loop calculation or a unitary regulator. Thus the significance is potentially high but currently conditional.
major comments (3)
- [Section 6 / Abstract] Section 6 states: 'we did not properly discuss the gravitational dressing of the external operators.' This is not a side remark: the abstract promises a gauge-invariant definition by dressing to an observer, and the entire positive-growth result depends on large-diffeomorphism pieces (eq. (4.21) for the L=0 mode; §4.4 for the L=1 sector) whose contribution to a dressed observable is never computed. In parallel, §4.3 shows that the tree-level L=1 divergence is removed by imposing matter constraints. Without a dressed-observable computation showing that the L=0 and L=1 large-diffeomorphism phases survive with the same coefficient, the growth in eqs. (5.67) and (5.30) is not established for a gauge-invariant OTOC.
- [Section 4.4 / eq. (5.67)] The paper admits in §4.4 that the answer is 'sensitive to the integration contour choice' for general kinematics, and the Discussion repeats that the growing contribution makes the result contour-sensitive. Equation (5.67) is obtained through a specific analytic continuation (ϵ_1=-π, etc., and e^{t41/ℓ}→-i e^{t/ℓ}). If the leading large-diffeomorphism term is contour-dependent, then the sign C_massless>0 and the coefficient in (5.67) are not uniquely determined by the calculation. The authors need to specify the physical contour selected by the observer worldline or by the dressing procedure and show that (5.67) is either contour-independent or the correct physical prescription.
- [Sections 4.3, 4.5, 5.3] The loop-level claim (Abstract; §1.1; eqs. (5.28)–(5.30)) is not supported by an explicit loop computation. The logarithmic divergence of the vector part of the propagator (4.14) is identified in the tree-level eikonal integral; the statement that it becomes a 'genuine divergence' at loop level because it lives in internal graviton propagators (Discussion) is an assertion. Moreover, the m_g regulator of §4.5 is a non-unitary massive-graviton deformation, and the double-scaling limit is taken with G_N e^{t/ℓ}/m_g^2 fixed. Since the claimed λ_L=4π/β_dS result is derived entirely within this regulator, a reader cannot distinguish a physical Lyapunov exponent from a regulator artifact. A direct loop calculation retaining the dressing, or a unitary/invariant regularization, is required.
minor comments (5)
- [Section 5.2, eq. (5.11)] The notation t*_i appears in ψ_1 and ψ_2 without an explicit definition. It should be defined near eq. (5.11), e.g. as the antipodal time shift t* = t + iπℓ, to avoid confusion with the Euclidean regulators ϵ_i used later.
- [Section 5.5] Typo: 'pode–antipode configuration' should be 'pole–antipode configuration'.
- [Figures 6 and 7] The horizontal axes are labeled by -iμ or μ, but the ranges and the meaning of Re(f) in these plots are not fully explained in the captions. The values are also extremely large (e.g. ~10^12); a brief statement about normalization and the role of the ϵ regulator would help.
- [References] Reference [31] is listed as 'work in progress' (2026). This is not a citable reference for the present paper; it should be removed or replaced by a preprint number if available.
- [Section 6 / [4]] The discussion of the MSS bound would benefit from a more explicit statement of why the bound is expected to apply to the dS static-patch observer setup, given that there is no asymptotic boundary and the dressing is not specified. The reference to the doubled SYK model is suggestive but no quantitative comparison is made.
Circularity Check
No circularity: OTOC growth is a direct evaluation of stated propagator/wavefunction inputs; dressing and contour caveats are robustness gaps, not definitional circularity.
full rationale
The paper contains no fitted parameters and no ex-post adjustments. The eikonal phase is computed from the de Sitter graviton propagator (eqs. 4.15, 4.21, 4.32, using the external propagator results [22-24]); the wavefunctions are Fourier transforms of the free de Sitter two-point function (5.11, 5.19); and the OTOC is assembled with the standard eikonal/OTOC machinery of [17,18]. The two headline results follow by direct evaluation: the tree-level growth (5.66)-(5.67) comes from the sign of the L=0 eigenvalue in the transverse Green function, and the regulated even-power selection rule (5.27)-(5.30) follows from the angular integral (E.3), with the e^{2t/ell} factor arising arithmetically from the surviving k=1 term. No parameter is adjusted to match the quoted growth; the mass regulator and double-scaling limit are stated kinematic choices, and the paper itself labels the massless result as reliable only at tree level ('Because of the underlying IR issue... reliable only at tree level', Sec. 5). The principal caveats are physical robustness issues rather than circularity: Sec. 4.4 admits 'sensitivity to the integration contour choice' and Sec. 6 admits 'we did not properly discuss the gravitational dressing of the external operators.' These undermine the gauge-invariance of the observable but do not make the derivation identical to its inputs. Self-citations ([2], [4], [30]) appear only in the interpretive discussion of the doubled-SYK model and the bound-on-chaos tension; they are not load-bearing for the computation. The derivation is therefore self-contained in the sense relevant to circularity: the asserted growth is a computed consequence of stated propagator and wavefunction inputs, not a restatement of those inputs.
Axiom & Free-Parameter Ledger
free parameters (3)
- graviton mass regulator m_g =
m_g → 0, G_N e^{t/ℓ}/m_g² fixed
- gauge-fixing parameters (α, β) =
none (probes α, β dependence)
- Euclidean time-shift regulators ϵ_i =
ϵ = 0.001 in Figs. 6–7; ϵ_i = {-π, -π/2, 0, π/2}ℓ in the chaos-bound configuration
axioms (6)
- domain assumption Graviton propagator on dS as given by [22–25]
- domain assumption Eikonal approximation: generalized ladder diagrams dominate and exponentiate for large center-of-mass energy in graviton exchange
- ad hoc to paper Observer dressing, invoked to make the OTOC gauge-invariant, does not alter the eikonal phase or external-line couplings used here
- domain assumption Large diffeomorphisms that do not decay at infinity contribute a non-vanishing, physical shift to the eikonal phase in dS (unlike AdS)
- ad hoc to paper The vector-sector IR divergence in the graviton propagator survives to genuine loop-level divergences in the OTOC
- standard math Standard QFT analytic continuation (iϵ prescriptions; Euclidean rotation (3.24); Bunch–Davies wavefunction conventions)
invented entities (2)
-
Massive graviton regulator (m_g)
no independent evidence
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Large diffeomorphisms acting as physical carriers of the eikonal phase and OTOC growth
no independent evidence
read the original abstract
We study the 4-point out-of-time-ordered correlator (OTOC) of scalar fields using the eikonal approximation to gravity around a de Sitter background. It can be defined in a gauge-invariant way by dressing the operators to an observer. We consider de Sitter space in any dimension and any bulk masses of the scalar fields. At tree level we find the maximal Lyapunov exponent of $2 \pi/\beta_{\rm dS}$. However, we describe an IR problem in this calculation at the loop level associated with the vector part of the graviton propagator. Regularizing this divergence leads to the vanishing of all odd powers in Newton's constant in the asymptotic expansion, so that the leading answer comes with twice the maximal Lyapunov exponent in simple operator configurations. We find that the perturbative OTOC in de Sitter can initially grow, which is not allowed by the quantum bound on chaos. Interestingly, we find that this growth is mediated by large diffeomorphisms in the graviton propagator.
Figures
Forward citations
Cited by 2 Pith papers
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Observer correlators in de Sitter exhibit anti-scrambling with a positive OTOC correction and 2π/β Lyapunov exponent, and a Euclidean-folding prescription for bounded-energy quantum systems is proposed.
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Anti-scrambling and euclidean folds from observer correlators in de Sitter space
Semiclassical gravity in de Sitter space produces four-point observer correlators whose sign of the scrambling correction is opposite to the black-hole case (anti-scrambling); the authors propose bounded-energy quantu...
Reference graph
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