Cancellation of one-loop time dependence in superhorizon curvature perturbations from all scales
Pith reviewed 2026-06-29 02:30 UTC · model grok-4.3
The pith
The apparent time dependence of the one-loop curvature power spectrum cancels when all loop scales and boundary terms are combined consistently.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
In spatially-flat gauge, the one-loop curvature power spectrum on superhorizon scales shows no residual time dependence once the nonlinear δN relation between inflaton fluctuations and curvature perturbations is used and all contributions, including boundary terms from loop integrals over every scale, are retained consistently.
What carries the argument
The δN formalism that nonlinearly relates inflaton fluctuations to curvature perturbations, applied while integrating loop modes over all wavenumbers without a k ≫ q assumption and retaining boundary terms.
If this is right
- Superhorizon curvature perturbations are conserved at one-loop order for any loop wavenumber.
- The curvature power spectrum can be computed without restricting to k much larger than the external mode q.
- Boundary terms must be kept to obtain a time-independent result.
- The cancellation holds in spatially-flat gauge when the δN relation is used throughout.
Where Pith is reading between the lines
- Similar all-scale consistency might remove time dependence in higher-loop or multi-field calculations.
- Gauge-invariant observables could require explicit retention of boundary contributions whenever nonlinear field redefinitions are involved.
- Numerical checks of the power spectrum at fixed superhorizon times could test whether the cancellation persists beyond analytic approximations.
Load-bearing premise
The nonlinear mapping from inflaton fluctuations to curvature perturbations given by the δN formalism stays valid at one-loop order with no additional gauge or interaction corrections.
What would settle it
An explicit recomputation of the one-loop power spectrum that keeps the k ≲ q regime and boundary terms yet still finds uncancelled time dependence on superhorizon scales.
Figures
read the original abstract
We show the conservation of the superhorizon curvature perturbations at one-loop level in spatially-flat gauge, including contributions from loop wavenumbers on all scales. In contrast to previous works, we do not assume a hierarchy $k \gg q$ between the wavenumber of the loop integral, $k$, and that of the power spectrum, $q$, and we explicitly include the regime $k \lesssim q$. Taking into account the nonlinear relation between the inflaton fluctuation and the curvature perturbation with the $\delta N$ formalism, we show that the apparent time dependence of the one-loop curvature power spectrum cancels once all contributions, including boundary terms, are combined consistently.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript claims that the apparent time dependence in the one-loop superhorizon curvature power spectrum cancels when all loop contributions (including from modes with k ≲ q) are combined consistently with boundary terms, using the nonlinear δN relation between inflaton fluctuations and ζ in spatially-flat gauge, without assuming a scale hierarchy.
Significance. If the cancellation holds after all scales and terms are included, the result would confirm conservation of superhorizon ζ at one-loop order and strengthen the reliability of δN-based calculations of loop corrections to the power spectrum and non-Gaussianity. The absence of free parameters in the final cancellation and the explicit treatment of the full k-range are strengths.
major comments (1)
- [δN formalism application (abstract and main derivation sections)] The central cancellation result rests on the assumption that the δN mapping from inflaton fluctuation to ζ remains exact at one-loop order with no additional gauge or interaction corrections when the loop integral includes modes with k ≲ q. This assumption is load-bearing for the claim that all contributions combine to cancel time dependence, yet the manuscript does not provide an explicit verification or counterterm analysis for the non-hierarchical regime.
minor comments (1)
- Clarify the precise definition and handling of boundary terms in the one-loop integrals to ensure reproducibility.
Simulated Author's Rebuttal
We thank the referee for their careful reading of the manuscript and for highlighting the importance of the δN formalism's applicability across all scales. We address the single major comment below.
read point-by-point responses
-
Referee: [δN formalism application (abstract and main derivation sections)] The central cancellation result rests on the assumption that the δN mapping from inflaton fluctuation to ζ remains exact at one-loop order with no additional gauge or interaction corrections when the loop integral includes modes with k ≲ q. This assumption is load-bearing for the claim that all contributions combine to cancel time dependence, yet the manuscript does not provide an explicit verification or counterterm analysis for the non-hierarchical regime.
Authors: The δN formalism supplies the exact, nonlinear relation between the inflaton fluctuation δφ (in spatially flat gauge) and the curvature perturbation ζ on uniform-density slices; this relation follows directly from the definition of ζ and holds order by order without further gauge or interaction corrections at one-loop level. Our calculation implements this mapping uniformly for every mode in the loop integral, with no scale hierarchy imposed and with the regime k ≲ q treated on the same footing as k ≫ q. All time-dependent pieces, including those arising from the nonlinear expansion and the associated boundary terms, are retained and shown to cancel identically once the full set of contributions is assembled. Because the cancellation is obtained by direct, consistent application of the δN relation over the complete k range, a separate counterterm analysis is not required at this perturbative order; the result is parameter-free and follows from the gauge-invariant construction itself. revision: no
Circularity Check
No significant circularity; derivation uses established external δN formalism
full rationale
The paper's central result is a perturbative cancellation of apparent time dependence in the one-loop superhorizon curvature power spectrum when all scales (including k ≲ q) and boundary terms are included. This is obtained by applying the standard δN formalism to relate inflaton fluctuations to ζ, which is an independent, externally established relation from prior literature and not derived or fitted inside the paper. No self-citation chains, self-definitional reductions, fitted inputs renamed as predictions, or ansatzes smuggled via author citations are present in the described derivation. The calculation is self-contained against external benchmarks once the δN mapping is granted.
Axiom & Free-Parameter Ledger
axioms (2)
- domain assumption δN formalism applies to relate inflaton fluctuations to curvature perturbations at one-loop level
- domain assumption Spatially-flat gauge is suitable for the one-loop calculation of curvature perturbations
Reference graph
Works this paper leans on
-
[1]
In our previous works, we focused on the situation where the linear relation between them is a good approximation for simplicity
We take into account the nonlinear relation between the curvature perturbationζand the inflaton fluctuation δϕin spatially-flat gauge. In our previous works, we focused on the situation where the linear relation between them is a good approximation for simplicity. In this work, we will see that the loop contributions fromk≲qgenerally cancel through the no...
-
[2]
8 ˆ τ τi dτ ′a4(τ ′)V(3)(τ ′)Im[u0(τ)u ∗ 0(τ ′)] 1 ˙¯ϕ(τ) T(q, τ f , τ ′, τi) +C(q, τ f , τi) # = 2π2 q3 Pζ,tr(q)
We consider the transition: the initial period→slow-roll (SR) period→the late period. We assume that the tree-level curvature perturbations onk≲qremain constant after the initial period. In contrast to our previous works, we do not assumeV (3) = 0 (V(3): third derivative of the inflaton potential) for any of the above periods, including the SR period. We ...
-
[3]
V. F. Mukhanov and G. V. Chibisov, JETP Lett.33, 532 (1981)
1981
-
[4]
V. F. Mukhanov and G. V. Chibisov, Sov. Phys. JETP56, 258 (1982)
1982
-
[5]
A. A. Starobinsky, Phys. Lett. B117, 175 (1982)
1982
-
[6]
A. H. Guth and S. Y. Pi, Phys. Rev. Lett.49, 1110 (1982)
1982
-
[7]
Panagiotakopoulos, A
C. Panagiotakopoulos, A. Salam, and J. A. Strathdee, Phys. Lett. B115, 29 (1982)
1982
-
[8]
J. M. Bardeen, P. J. Steinhardt, and M. S. Turner, Phys. Rev. D28, 679 (1983)
1983
-
[9]
G. F. Chapline, Nature253, 251 (1975)
1975
-
[10]
Ivanov, P
P. Ivanov, P. Naselsky, and I. Novikov, Phys. Rev. D50, 7173 (1994)
1994
-
[11]
J. Yokoyama, Astron. Astrophys.318, 673 (1997), arXiv:astro-ph/9509027
Pith/arXiv arXiv 1997
-
[12]
J. Garcia-Bellido, A. D. Linde, and D. Wands, Phys. Rev.D54, 6040 (1996), arXiv:astro-ph/9605094 [astro-ph]
Pith/arXiv arXiv 1996
-
[13]
N. Afshordi, P. McDonald, and D. N. Spergel, Astrophys. J. Lett.594, L71 (2003), arXiv:astro-ph/0302035
Pith/arXiv arXiv 2003
-
[14]
P. H. Frampton, M. Kawasaki, F. Takahashi, and T. T. Yanagida, JCAP1004, 023 (2010), arXiv:1001.2308 [hep-ph]
Pith/arXiv arXiv 2010
-
[15]
K. M. Belotsky, A. D. Dmitriev, E. A. Esipova, V. A. Gani, A. V. Grobov, M. Y. Khlopov, A. A. Kirillov, S. G. Rubin, and I. V. Svadkovsky, Mod. Phys. Lett. A29, 1440005 (2014), arXiv:1410.0203 [astro-ph.CO]
Pith/arXiv arXiv 2014
-
[16]
B. Carr, F. Kuhnel, and M. Sandstad, Phys. Rev.D94, 083504 (2016), arXiv:1607.06077 [astro-ph.CO]
Pith/arXiv arXiv 2016
-
[17]
K. Inomata, M. Kawasaki, K. Mukaida, Y. Tada, and T. T. Yanagida, Phys. Rev.D96, 043504 (2017), arXiv:1701.02544 [astro-ph.CO]
Pith/arXiv arXiv 2017
-
[18]
J. R. Espinosa, D. Racco, and A. Riotto, Phys. Rev. Lett.120, 121301 (2018), arXiv:1710.11196 [hep-ph]
Pith/arXiv arXiv 2018
-
[19]
S. Bird, I. Cholis, J. B. Mu˜ noz, Y. Ali-Ha¨ ımoud, M. Kamionkowski, E. D. Kovetz, A. Raccanelli, and A. G. Riess, Phys. Rev. Lett.116, 201301 (2016), arXiv:1603.00464 [astro-ph.CO]
Pith/arXiv arXiv 2016
-
[20]
S. Clesse and J. Garc´ ıa-Bellido, Phys. Dark Univ.10, 002 (2016), arXiv:1603.05234 [astro-ph.CO]
Pith/arXiv arXiv 2016
-
[21]
M. Sasaki, T. Suyama, T. Tanaka, and S. Yokoyama, Phys. Rev. Lett.117, 061101 (2016), arXiv:1603.08338 [astro-ph.CO]
Pith/arXiv arXiv 2016
-
[22]
Y. N. Eroshenko, J. Phys. Conf. Ser.1051, 012010 (2018), arXiv:1604.04932 [astro-ph.CO]
Pith/arXiv arXiv 2018
-
[23]
M. Sasaki, T. Suyama, T. Tanaka, and S. Yokoyama, Class. Quant. Grav.35, 063001 (2018), arXiv:1801.05235 [astro- ph.CO]
Pith/arXiv arXiv 2018
-
[24]
B. Carr, K. Kohri, Y. Sendouda, and J. Yokoyama, Rept. Prog. Phys.84, 116902 (2021), arXiv:2002.12778 [astro-ph.CO]
Pith/arXiv arXiv 2021
-
[25]
A. M. Green and B. J. Kavanagh, J. Phys. G48, 043001 (2021), arXiv:2007.10722 [astro-ph.CO]
Pith/arXiv arXiv 2021
-
[26]
A. Escriv` a, F. Kuhnel, and Y. Tada, (2022), 10.1016/B978-0-32-395636-9.00012-8, arXiv:2211.05767 [astro-ph.CO]
-
[27]
Agazieet al.(NANOGrav), Astrophys
G. Agazieet al.(NANOGrav), Astrophys. J. Lett.951, L8 (2023), arXiv:2306.16213 [astro-ph.HE]
Pith/arXiv arXiv 2023
-
[28]
Afzalet al.(NANOGrav), Astrophys
A. Afzalet al.(NANOGrav), Astrophys. J. Lett.951, L11 (2023), arXiv:2306.16219 [astro-ph.HE]
Pith/arXiv arXiv 2023
-
[29]
Antoniadiset al.(EPTA, InPTA:), Astron
J. Antoniadiset al.(EPTA, InPTA:), Astron. Astrophys.678, A50 (2023), arXiv:2306.16214 [astro-ph.HE]
Pith/arXiv arXiv 2023
-
[30]
Antoniadiset al.(EPTA, InPTA), Astron
J. Antoniadiset al.(EPTA, InPTA), Astron. Astrophys.685, A94 (2024), arXiv:2306.16227 [astro-ph.CO]
arXiv 2024
-
[31]
D. J. Reardonet al., Astrophys. J. Lett.951, L6 (2023), arXiv:2306.16215 [astro-ph.HE]
Pith/arXiv arXiv 2023
-
[32]
H. Xuet al., Res. Astron. Astrophys.23, 075024 (2023), arXiv:2306.16216 [astro-ph.HE]
Pith/arXiv arXiv 2023
-
[33]
S. Weinberg, Phys. Rev. D72, 043514 (2005), arXiv:hep-th/0506236
Pith/arXiv arXiv 2005
-
[34]
L. Senatore and M. Zaldarriaga, JHEP12, 008 (2010), arXiv:0912.2734 [hep-th]
Pith/arXiv arXiv 2010
-
[35]
J. Kristiano and J. Yokoyama, Phys. Rev. Lett.132, 221003 (2024), arXiv:2211.03395 [hep-th]
arXiv 2024
-
[36]
Riotto, (2023), arXiv:2301.00599 [astro-ph.CO]
A. Riotto, (2023), arXiv:2301.00599 [astro-ph.CO]. 29
arXiv 2023
-
[37]
S. Choudhury, M. R. Gangopadhyay, and M. Sami, Eur. Phys. J. C84, 884 (2024), arXiv:2301.10000 [astro-ph.CO]
arXiv 2024
-
[38]
J. Kristiano and J. Yokoyama, Phys. Rev. D109, 103541 (2024), arXiv:2303.00341 [hep-th]
arXiv 2024
-
[39]
Riotto, (2023), arXiv:2303.01727 [astro-ph.CO]
A. Riotto, (2023), arXiv:2303.01727 [astro-ph.CO]
arXiv 2023
-
[40]
Firouzjahi, JCAP10, 006 (2023), arXiv:2303.12025 [astro-ph.CO]
H. Firouzjahi, JCAP10, 006 (2023), arXiv:2303.12025 [astro-ph.CO]
arXiv 2023
-
[41]
H. Motohashi and Y. Tada, JCAP08, 069 (2023), arXiv:2303.16035 [astro-ph.CO]
arXiv 2023
-
[42]
H. Firouzjahi and A. Riotto, JCAP02, 021 (2024), arXiv:2304.07801 [astro-ph.CO]
arXiv 2024
-
[43]
G. Franciolini, A. Iovino, Junior., M. Taoso, and A. Urbano, Phys. Rev. D109, 123550 (2024), arXiv:2305.03491 [astro- ph.CO]
arXiv 2024
- [44]
-
[45]
S.-L. Cheng, D.-S. Lee, and K.-W. Ng, JCAP03, 008 (2024), arXiv:2305.16810 [astro-ph.CO]
arXiv 2024
- [46]
-
[47]
H. Firouzjahi, Phys. Rev. D109, 043514 (2024), arXiv:2311.04080 [astro-ph.CO]
arXiv 2024
-
[48]
M. W. Davies, L. Iacconi, and D. J. Mulryne, JCAP04, 050 (2024), arXiv:2312.05694 [astro-ph.CO]
arXiv 2024
-
[49]
L. Iacconi, D. Mulryne, and D. Seery, JCAP06, 062 (2024), arXiv:2312.12424 [astro-ph.CO]
arXiv 2024
-
[50]
S. Saburov and S. V. Ketov, Universe10, 354 (2024), arXiv:2402.02934 [gr-qc]
arXiv 2024
-
[51]
G. Ballesteros and J. G. Egea, JCAP07, 052 (2024), arXiv:2404.07196 [astro-ph.CO]
arXiv 2024
-
[52]
J. Kristiano and J. Yokoyama, JCAP10, 036 (2024), arXiv:2405.12145 [astro-ph.CO]
arXiv 2024
-
[53]
J. Kristiano and J. Yokoyama, “Generating Large Primordial Fluctuations in Single-Field Inflation for Primordial Black Hole Formation,” (2025) arXiv:2405.12149 [astro-ph.CO]
arXiv 2025
-
[54]
H. Sheikhahmadi and A. Nassiri-Rad, (2024), arXiv:2411.18525 [astro-ph.CO]
arXiv 2024
-
[55]
D. Frolovsky and S. V. Ketov, Phys. Rev. D111, 083533 (2025), arXiv:2502.00628 [gr-qc]
arXiv 2025
-
[56]
Fumagalli, JHEP05, 162 (2025), arXiv:2305.19263 [astro-ph.CO]
J. Fumagalli, JHEP05, 162 (2025), arXiv:2305.19263 [astro-ph.CO]
arXiv 2025
-
[57]
Y. Tada, T. Terada, and J. Tokuda, JHEP01, 105 (2024), arXiv:2308.04732 [hep-th]
arXiv 2024
-
[58]
K. Inomata, Phys. Rev. Lett.133, 141001 (2024), arXiv:2403.04682 [astro-ph.CO]
arXiv 2024
-
[59]
R. Kawaguchi, S. Tsujikawa, and Y. Yamada, JHEP12, 095 (2024), arXiv:2407.19742 [hep-th]
arXiv 2024
-
[60]
Fumagalli, JHEP01, 108 (2025), arXiv:2408.08296 [astro-ph.CO]
J. Fumagalli, JHEP01, 108 (2025), arXiv:2408.08296 [astro-ph.CO]
arXiv 2025
- [61]
-
[62]
C.-J. Fang, Z.-H. Lyu, C. Chen, and Z.-K. Guo, Phys. Rev. D112, 023547 (2025), arXiv:2502.09555 [gr-qc]
arXiv 2025
- [63]
-
[64]
C.-J. Fang, Z.-H. Lyu, C. Chen, and Z.-K. Guo, (2025), arXiv:2507.00077 [astro-ph.CO]
Pith/arXiv arXiv 2025
-
[65]
M. Braglia and L. Pinol, Phys. Rev. D113, 063513 (2026), arXiv:2504.07926 [astro-ph.CO]
arXiv 2026
-
[66]
M. Braglia and L. Pinol, Phys. Rev. D113, L061302 (2026), arXiv:2504.13136 [astro-ph.CO]
arXiv 2026
- [67]
- [68]
-
[69]
Y. Ema, M. Hong, R. Jinno, and K. Mukaida, (2026), arXiv:2603.01961 [astro-ph.CO]
arXiv 2026
- [70]
-
[71]
D. H. Lyth, K. A. Malik, and M. Sasaki, JCAP05, 004 (2005), arXiv:astro-ph/0411220
Pith/arXiv arXiv 2005
-
[72]
D. Langlois and F. Vernizzi, Phys. Rev. D72, 103501 (2005), arXiv:astro-ph/0509078
Pith/arXiv arXiv 2005
-
[73]
G. L. Pimentel, L. Senatore, and M. Zaldarriaga, JHEP07, 166 (2012), arXiv:1203.6651 [hep-th]
Pith/arXiv arXiv 2012
-
[74]
G. Ballesteros, J. G. Egea, and F. Riccardi, (2025), arXiv:2512.20467 [hep-th]
Pith/arXiv arXiv 2025
-
[75]
M. Braglia, S. C´ espedes, and L. Pinol, (2026), arXiv:2603.12216 [astro-ph.CO]
arXiv 2026
- [76]
-
[77]
D. Baumann and D. Green, JCAP09, 014 (2011), arXiv:1102.5343 [hep-th]
Pith/arXiv arXiv 2011
-
[78]
E. Pajer, G. L. Pimentel, and J. V. S. Van Wijck, JCAP06, 009 (2017), arXiv:1609.06993 [hep-th]
Pith/arXiv arXiv 2017
-
[79]
J. M. Maldacena, JHEP05, 013 (2003), arXiv:astro-ph/0210603
Pith/arXiv arXiv 2003
-
[80]
A. Caravano, E. Komatsu, K. D. Lozanov, and J. Weller, JCAP12, 010 (2021), arXiv:2102.06378 [astro-ph.CO]
arXiv 2021
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.