The imprints of massive neutrinos on the three-point correlation function of large-scale structures
Pith reviewed 2026-05-16 20:57 UTC · model grok-4.3
The pith
The three-point correlation function shows distinct massive-neutrino signals on elongated and right-angled triangles that differ from sigma_8 variations.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Measurements of ζ and Q on halo catalogs from the Quijote simulations reveal that neutrino free-streaming produces its strongest signal in quasi-isosceles and squeezed triangles, increasing toward lower redshifts. Elongated triangles are most affected in ζ while right-angled triangles supply a complementary source in Q. Direct comparison with simulations that vary sigma_8 without neutrinos shows these signatures are significantly different, indicating that the three-point correlation function can break the M_ν–σ_8 degeneracy.
What carries the argument
The isotropic connected three-point correlation function ζ and reduced three-point correlation function Q evaluated on different triangle shapes in simulated halo distributions.
If this is right
- Elongated triangles in ζ become the primary probe for isolating neutrino-mass effects in future galaxy surveys.
- Right-angled triangles in Q supply an independent channel less entangled with sigma_8.
- The neutrino signal strengthens at lower redshifts, favoring lower-redshift bins in survey analyses.
- The triangle-shape framework can be applied directly to data from DESI, Euclid, 4MOST, and the Roman Space Telescope.
Where Pith is reading between the lines
- The same shape-dependent analysis could be extended to other degenerate parameter pairs in large-scale structure studies.
- Combining three-point correlation function measurements with two-point statistics may tighten neutrino-mass bounds beyond what either probe achieves separately.
- Real survey data will ultimately test whether the simulated differences persist once observational systematics are included.
Load-bearing premise
The Quijote N-body simulations accurately capture the free-streaming effects of massive neutrinos on halo clustering without significant contamination from resolution limits or other modeling choices.
What would settle it
If measurements from a stage-IV spectroscopic survey find that the three-point correlation function differences on elongated triangles in ζ and right-angled triangles in Q match those produced by sigma_8 variations alone, the claim that the 3PCF breaks the degeneracy would be falsified.
Figures
read the original abstract
Free-streaming of cosmic neutrinos affects the distribution and growth of cosmic structures on small scales. This enables the sum of neutrino masses $M_\nu$ to be constrained from clustering studies. We investigate the possibility of disentangling massive neutrino cosmologies with the three-point correlation function (3PCF) for the first time. We measured the isotropic connected 3PCF $\zeta$ and the reduced 3PCF $Q$ of halo catalogs from the Quijote suite of $N$-body simulations, considering $M_\nu =0.0, 0.1, 0.2,$ and $0.4 \, \mathrm{eV}$ in different redshift bins. We developed a framework to quantify the detectability of massive neutrinos for different triangle configurations and shapes, and applied it to a case compatible with a stage-IV spectroscopic survey. We also compared our results with the analysis of simulations without neutrinos, but with different $\sigma_8$ values, to test whether the 3PCF can break the well-known degeneracy between the two parameters. We found that as a result of free-streaming, the strongest signal is found for quasi-isosceles and squeezed triangles; this signal increases for decreasing redshifts. Among these configurations, elongated triangles, tracing the filamentary structure of the cosmic web, are the most affected by massive neutrinos, with a 3PCF signal increasing with $M_\nu$. A complementary source of signal comes from right-angled triangles in $Q$. Importantly, we found that the signatures of a $\sigma_8$ variation appear to be significantly different on elongated triangles in $\zeta$ and right-angled triangles in $Q$, suggesting that the 3PCF can be used to effectively break the $M_\nu - \sigma_8$ degeneracy. These results open the possibility to use the 3PCF as a powerful complementary tool for constraining neutrino masses in current and future spectroscopic surveys such as DESI, Euclid, 4MOST, and the Nancy Grace Roman Space Telescope.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript claims that measurements of the isotropic connected three-point correlation function ζ and reduced three-point correlation function Q from halo catalogs in the Quijote N-body suite (M_ν = 0.0, 0.1, 0.2, 0.4 eV) show the strongest neutrino free-streaming signals on quasi-isosceles, squeezed, and elongated triangles in ζ and right-angled triangles in Q. These signatures differ from those produced by σ8 variations, enabling the 3PCF to break the M_ν-σ8 degeneracy. A detectability framework is developed and applied to a stage-IV spectroscopic survey case, with signals strengthening toward lower redshifts.
Significance. If the central results hold, the work would be significant for large-scale structure cosmology by identifying specific 3PCF triangle configurations that respond differently to neutrino free-streaming than to σ8, offering a practical complement to two-point statistics for neutrino mass constraints in surveys such as DESI, Euclid, and Roman. The use of the public Quijote suite with direct triangle counting across multiple masses and redshifts, plus the explicit detectability framework, provides a reproducible foundation for follow-up analyses.
major comments (1)
- The degeneracy-breaking claim (abstract) requires that differences in elongated triangles for ζ and right-angled triangles for Q between the M_ν runs and the σ8-varied runs arise purely from neutrino free-streaming. The Quijote setup deploys 512^3 CDM particles in 1 Gpc/h volumes with neutrinos as additional particles; for M_ν = 0.1–0.4 eV the free-streaming wavenumber lies near the resolution limit, where neutrino shot noise and force softening can alter small-scale halo clustering. No convergence tests of the 3PCF versus particle number or neutrino assignment scheme are referenced, so numerical artifacts would not cancel in the σ8 comparison and could mimic the reported distinct signatures.
minor comments (2)
- The abstract mentions both 'quasi-isosceles and squeezed triangles' and 'elongated triangles' as most affected; a short explicit statement of how these shape classes relate (e.g., via opening-angle or side-length ratios) would improve clarity.
- Details on covariance estimation, triangle binning, and error-bar construction for the detectability framework should be expanded in the methods section to allow full reproducibility of the stage-IV forecast.
Simulated Author's Rebuttal
We thank the referee for their thorough review and valuable feedback on our manuscript. We have carefully considered the major comment and provide our response below, along with plans for revision.
read point-by-point responses
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Referee: The degeneracy-breaking claim (abstract) requires that differences in elongated triangles for ζ and right-angled triangles for Q between the M_ν runs and the σ8-varied runs arise purely from neutrino free-streaming. The Quijote setup deploys 512^3 CDM particles in 1 Gpc/h volumes with neutrinos as additional particles; for M_ν = 0.1–0.4 eV the free-streaming wavenumber lies near the resolution limit, where neutrino shot noise and force softening can alter small-scale halo clustering. No convergence tests of the 3PCF versus particle number or neutrino assignment scheme are referenced, so numerical artifacts would not cancel in the σ8 comparison and could mimic the reported distinct signatures.
Authors: We appreciate the referee pointing out the potential for numerical artifacts in the neutrino simulations. The Quijote suite uses 512^3 CDM particles and additional neutrino particles, and while the free-streaming scales for the considered M_ν values are indeed near the resolution limit, our measurements focus on triangle configurations where the signal is dominated by large-scale modes less affected by small-scale noise. The σ8-varied simulations share the same CDM resolution, facilitating a fair comparison of the shape-dependent responses. However, we agree that explicit convergence tests for the 3PCF are necessary to fully substantiate the claims. In the revised manuscript, we will add a dedicated section presenting convergence checks, including comparisons with available higher-resolution Quijote runs and assessments of neutrino particle loading effects, to confirm that the distinct signatures in elongated triangles for ζ and right-angled triangles for Q are physical and not artifacts. This will strengthen the degeneracy-breaking argument. revision: yes
Circularity Check
No circularity: results obtained via direct counting in N-body catalogs
full rationale
The paper reports measurements of the isotropic connected 3PCF ζ and reduced 3PCF Q extracted by direct enumeration of triangle configurations in halo catalogs drawn from the Quijote N-body suite. No analytic derivation, fitted functional form, or self-citation chain is invoked to obtain the reported signals on elongated or right-angled triangles; the differences between M_ν and σ_8 runs are presented as numerical outcomes of the simulation measurements themselves. The framework for detectability is likewise a post-processing quantification applied to those counts. Because the central claims rest on external simulation data rather than on any equation that reduces to its own inputs by construction, the derivation chain contains no circular steps.
Axiom & Free-Parameter Ledger
free parameters (1)
- M_nu simulation values
axioms (1)
- domain assumption Quijote N-body simulations accurately reproduce the effects of neutrino free-streaming on halo clustering
Lean theorems connected to this paper
-
IndisputableMonolith/Cost/FunctionalEquation.leanwashburn_uniqueness_aczel unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
We measure the isotropic connected 3PCF ζ and the reduced 3PCF Q of halo catalogs from the Quijote suite... to test whether the 3PCF can break the well-known degeneracy between the two parameters.
-
IndisputableMonolith/Foundation/RealityFromDistinction.leanreality_from_one_distinction unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
the signatures of a σ_8 variation appear to be significantly different on elongated triangles in ζ and right-angled triangles in Q
What do these tags mean?
- matches
- The paper's claim is directly supported by a theorem in the formal canon.
- supports
- The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
- extends
- The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
- uses
- The paper appears to rely on the theorem as machinery.
- contradicts
- The paper's claim conflicts with a theorem or certificate in the canon.
- unclear
- Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.
Reference graph
Works this paper leans on
-
[1]
, " * write output.state after.block = add.period write newline
ENTRY address archiveprefix author booktitle chapter edition editor howpublished institution eprint journal key month note number organization pages publisher school series title type volume year label extra.label sort.label short.list INTEGERS output.state before.all mid.sentence after.sentence after.block FUNCTION init.state.consts #0 'before.all := #1 ...
-
[2]
" write newline "" before.all 'output.state := FUNCTION n.dashify 't := "" t empty not t #1 #1 substring "-" = t #1 #2 substring "--" = not "--" * t #2 global.max substring 't := t #1 #1 substring "-" = "-" * t #2 global.max substring 't := while if t #1 #1 substring * t #2 global.max substring 't := if while FUNCTION word.in bbl.in " " * FUNCTION format....
-
[3]
Abdul Karim , M., Aguilar , J., Ahlen , S., et al. 2025, , 112, 083515
work page 2025
-
[4]
G., Aguilar , J., Ahlen , S., et al
Adame , A. G., Aguilar , J., Ahlen , S., et al. 2025, , 2025, 028
work page 2025
-
[5]
Albrecht , A., Bernstein , G., Cahn , R., et al. 2006, arXiv e-prints, astro
work page 2006
-
[6]
Bardeen , J. M., Bond , J. R., Kaiser , N., & Szalay , A. S. 1986, , 304, 15
work page 1986
-
[7]
Bernardeau , F., Colombi , S., Gazta \ n aga , E., & Scoccimarro , R. 2002, , 367, 1
work page 2002
-
[8]
R., Efstathiou , G., & Silk , J
Bond , J. R., Efstathiou , G., & Silk , J. 1980, , 45, 1980
work page 1980
-
[9]
Brandbyge , J., Hannestad , S., Haugb lle , T., & Thomsen , B. 2008, , 2008, 020
work page 2008
-
[10]
Brandbyge , J., Hannestad , S., Haugb lle , T., & Wong , Y. Y. Y. 2010, , 2010, 014
work page 2010
-
[11]
Castorina , E., Carbone , C., Bel , J., Sefusatti , E., & Dolag , K. 2015, , 2015, 043
work page 2015
-
[12]
K., Villaescusa-Navarro , F., & Viel , M
Castorina , E., Sefusatti , E., Sheth , R. K., Villaescusa-Navarro , F., & Viel , M. 2014, , 2014, 049
work page 2014
-
[13]
Celoria , M. & Matarrese , S. 2018, arXiv e-prints, arXiv:1812.08197
work page internal anchor Pith review Pith/arXiv arXiv 2018
- [14]
-
[15]
2011, European Physical Journal C, 71, 1554
Cowan , G., Cranmer , K., Gross , E., & Vitells , O. 2011, European Physical Journal C, 71, 1554
work page 2011
-
[16]
Davis , M., Efstathiou , G., Frenk , C. S., & White , S. D. M. 1985, , 292, 371
work page 1985
-
[17]
de Carvalho , E., Bernui , A., Xavier , H. S., & Novaes , C. P. 2020, , 492, 4469
work page 2020
-
[18]
de Jong , R. S., Agertz , O., Berbel , A. A., et al. 2019, The Messenger, 175, 3
work page 2019
-
[19]
The DESI Experiment Part I: Science,Targeting, and Survey Design
DESI Collaboration: Aghamousa , A., Aguilar , J., Ahlen , S., et al. 2016, arXiv e-prints, arXiv:1611.00036
work page internal anchor Pith review Pith/arXiv arXiv 2016
- [20]
- [21]
- [22]
-
[23]
2025, arXiv e-prints, arXiv:2506.22257
Euclid Collaboration: Guidi , M., Veropalumbo , A., Pugno , A., et al. 2025, arXiv e-prints, arXiv:2506.22257
- [24]
-
[25]
Euclid Collaboration: Scaramella , R., Amiaux , J., Mellier , Y., et al. 2022, , 662, A112
work page 2022
- [26]
-
[27]
2024, arXiv e-prints, arXiv:2408.03036
Farina , A., Veropalumbo , A., Branchini , E., & Guidi , M. 2024, arXiv e-prints, arXiv:2408.03036
-
[28]
Fisher , K. B. 1995, , 448, 494
work page 1995
-
[29]
Frieman , J. A. & Gaztanaga , E. 1994, , 425, 392
work page 1994
-
[30]
Fry , J. N. 1984, , 279, 499
work page 1984
-
[31]
Fry , J. N. 1994, , 73, 215
work page 1994
-
[32]
Fry , J. N. & Gaztanaga , E. 1993, , 413, 447
work page 1993
- [33]
-
[34]
Gazta \ n aga , E., Cabr \'e , A., Castander , F., Crocce , M., & Fosalba , P. 2009, , 399, 801
work page 2009
-
[35]
Gazta \ n aga , E., Norberg , P., Baugh , C. M., & Croton , D. J. 2005, , 364, 620
work page 2005
-
[36]
Grieb , J. N., S \'a nchez , A. G., Salazar-Albornoz , S., et al. 2017, , 467, 2085
work page 2017
-
[37]
Groth , E. J. & Peebles , P. J. E. 1977, , 217, 385
work page 1977
-
[38]
Guidi , M., Veropalumbo , A., Branchini , E., Eggemeier , A., & Carbone , C. 2023, , 2023, 066
work page 2023
- [39]
-
[40]
Hahn , C., Villaescusa-Navarro , F., Castorina , E., & Scoccimarro , R. 2020, , 2020, 040
work page 2020
-
[41]
Hamilton , A. J. S. 1992, , 385, L5
work page 1992
- [42]
-
[43]
R., Colombi , S., & Juszkiewicz , R
Hivon , E., Bouchet , F. R., Colombi , S., & Juszkiewicz , R. 1995, , 298, 643
work page 1995
- [44]
-
[45]
M., Simonovi \'c , M., & Zaldarriaga , M
Ivanov , M. M., Simonovi \'c , M., & Zaldarriaga , M. 2020, , 101, 083504
work page 2020
-
[46]
Jing , Y. P. & B \"o rner , G. 2004, , 607, 140
work page 2004
-
[47]
P., Borner , G., & Valdarnini , R
Jing , Y. P., Borner , G., & Valdarnini , R. 1995, , 277, 630
work page 1995
- [48]
- [49]
-
[50]
Kamalinejad , F. & Slepian , Z. 2025 a , arXiv e-prints, arXiv:2508.06759
- [51]
-
[52]
Landy , S. D. & Szalay , A. S. 1993, , 412, 64
work page 1993
-
[53]
Euclid Definition Study Report
Laureijs , R., Amiaux , J., Arduini , S., et al. 2011, arXiv e-prints, arXiv:1110.3193
work page internal anchor Pith review Pith/arXiv arXiv 2011
- [54]
-
[55]
Mainieri , V., Anderson , R. I., Brinchmann , J., et al. 2024, arXiv e-prints, arXiv:2403.05398
-
[56]
Mar \' n , F. A., Blake , C., Poole , G. B., et al. 2013, , 432, 2654
work page 2013
-
[57]
Marulli , F., Carbone , C., Viel , M., Moscardini , L., & Cimatti , A. 2011, , 418, 346
work page 2011
-
[58]
McBride , C. K., Connolly , A. J., Gardner , J. P., et al. 2011, , 739, 85
work page 2011
-
[59]
D., Green , D., Flauger , R., et al
Meerburg , P. D., Green , D., Flauger , R., et al. 2019, , 51, 107
work page 2019
-
[60]
Mo , H. J. & White , S. D. M. 1996, , 282, 347
work page 1996
-
[61]
Moresco , M., Marulli , F., Baldi , M., Moscardini , L., & Cimatti , A. 2014, , 443, 2874
work page 2014
-
[62]
Moresco , M., Veropalumbo , A., Marulli , F., Moscardini , L., & Cimatti , A. 2021, , 919, 144
work page 2021
-
[63]
Moretti , C., Tsedrik , M., Carrilho , P., & Pourtsidou , A. 2023, , 2023, 025
work page 2023
-
[64]
Nadal-Matosas , A., Gil-Mar \' n , H., & Verde , L. 2025, , 2025, 045
work page 2025
-
[65]
Navas , S., Amsler , C., Gutsche , T., et al. 2024, , 110, 030001
work page 2024
-
[66]
Oddo , A., Rizzo , F., Sefusatti , E., Porciani , C., & Monaco , P. 2021, , 2021, 038
work page 2021
- [67]
- [68]
-
[69]
Peebles , P. J. E. 1973, , 185, 413
work page 1973
-
[70]
Peebles , P. J. E. 1980, The Large-Scale Structure of the Universe (Princeton University Press)
work page 1980
-
[71]
Peebles , P. J. E. & Groth , E. J. 1975, , 196, 1
work page 1975
-
[72]
Peloso , M., Pietroni , M., Viel , M., & Villaescusa-Navarro , F. 2015, , 2015, 001
work page 2015
-
[73]
Philcox , O. H. E. 2021, , 104, 123529
work page 2021
-
[74]
Planck Collaboration , Aghanim , N., Akrami , Y., et al. 2020, , 641, A6
work page 2020
-
[75]
Pugno , A., Eggemeier , A., Porciani , C., & Kuruvilla , J. 2025, , 2025, 075
work page 2025
-
[76]
Ruggeri , R., Castorina , E., Carbone , C., & Sefusatti , E. 2018, , 2018, 003
work page 2018
-
[77]
S \'a nchez , A. G., Montesano , F., Kazin , E. A., et al. 2014, , 440, 2692
work page 2014
-
[78]
G., Scoccimarro , R., Crocce , M., et al
S \'a nchez , A. G., Scoccimarro , R., Crocce , M., et al. 2017, , 464, 1640
work page 2017
- [79]
-
[80]
Scoccimarro , R., Couchman , H. M. P., & Frieman , J. A. 1999, , 517, 531
work page 1999
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