Pith. sign in

REVIEW 5 major objections 5 minor 97 references

Amnesia in the Axion Misalignment Landscape

T0 review · 5 major / 5 minor · reviewed 2026-08-15 · deepseek-v4-flash

Challenge this review Re-run · record.json Download PDF Read on arXiv ↗ Review JSON

Pith's one-line read For axion decay constants below about 2×10^10 GeV, kinetic-misalignment axions fragment and then self-interact into the same small-scale spectrum as post-inflationary axions, erasing the initial misalignment history by matter–radiation…

desk verdict The summit-landing map and fragmentation physics are new and solid, but the headline amnesia claim rests on calibrated, regulator-dependent peak extraction that still needs an error budget. read the letter →

arxiv 2608.04139 v1 pith:KLKTAO7B submitted 2026-08-04 hep-ph astro-ph.COhep-th

Kierthika Chathirathas , Cem Eröncel , Mathieu Kaltschmidt , Javier Redondo , Kenichi Saikawa This is my paper · ORCID
classification hep-phastro-ph.COhep-th
keywords QCDaxionkineticmisalignmentfragmentationminiclustersstarslandscapelatticesimulationsmall-scaledarkmatterstructure
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

This paper tries to show that the QCD axion's small-scale dark-matter structure can be insensitive to how the axion was produced. In the pre-inflationary kinetic misalignment scenario, the axion starts with a large field velocity and traverses many potential barriers, so its evolution depends on both the initial angle $\Theta_1$ and velocity $v$; the authors map this two-dimensional landscape and identify fine-tuned 'summit-landing' branches where the field stops near a potential maximum. Using lattice simulations that follow fragmentation through the QCD crossover into the non-relativistic regime, they find that nonlinear fragmentation reduces the relic abundance by a dilution factor $D\sim 0.2$–$0.3$ at high velocity, and that strong self-interactions then drive the small-scale spectrum toward the same attractor previously found for post-inflationary axions. If this holds, for $f_A$ below about $2\times10^{10}$ GeV the initial history is erased: kinetic misalignment and post-inflationary axions produce essentially equivalent small-scale structure at matter–radiation equality, and minicluster or axion-star observations cannot distinguish the two scenarios.

What carries the argument

The load-bearing mechanism is an attractor from marginal self-interaction scattering. Non-relativistic $2a\to2a$ scattering with coupling $\lambda=\chi(T)/f_A^4$ redistributes axions toward higher momenta at a rate $\Gamma$, and because $\Gamma/H\propto m_A/(k_p^2 R^2)$, the spectral peak grows until $\Gamma/H\sim1$, giving $k_p\propto\sqrt{m_A}/R$ during radiation domination. This is simulated with a two-stage lattice setup: a relativistic code runs through fragmentation until axitons shrink below the grid, then a non-relativistic envelope equation is evolved with the 'fattening' regulator, which replaces $m_\psi$ by $\mu_{\rm fat}^2/(\delta x^2 m_\psi)$ only in the resummed potential and prevents unresolved wave-collapse into dense axion stars. The physical peak is extracted by masking the largest overdensities and fitting a two-component model that subtracts the artificial dense-axion-star peak. The paper also introduces the 'summit-landing' branch of the $(\Theta_1,v)$ landscape, where the field approaches a potential maximum with small residual velocity; the long residence near the unstable maximum produces a large amplification of fluctuations and a logarithmically enhanced relic abundance.

What would settle it

Rerun the non-relativistic evolution without the fattening regulator, or with a range of $\mu_{\rm fat}$ and box sizes such as $N=512^3$ and $1024^3$, and check whether the fitted peak $k_p^N(\eta_c)$ still follows the $30\,\mathrm{mpc}^{-1}(10^{10}\,\mathrm{GeV}/f_A)^{1.29}$ scaling; a regulator- or box-size-dependent peak would falsify the attractor claim. Alternatively, follow the relativistic simulation through the QCD crossover far enough to resolve axiton collapse directly and compare the resulting spectrum at matter–radiation equality with the post-inflationary attractor.

Watch

Extended reading notes

Core claim

The central discovery is that the late-time axion spectrum is an attractor: after fragmentation, the spectrum—and especially its peak—is driven to a value set by $f_A$ and $\Omega_A$ and largely independent of the previous history. The paper reports that the comoving number-spectrum peak settles at $k_p^N(\eta_c\to\eta_{\rm eq})\sim 30\,\mathrm{mpc}^{-1}(10^{10}\,\mathrm{GeV}/f_A)^{1.29}$ for $f_A\in(3\times10^8,\,10^{10})$ GeV, following the marginal-scattering trajectory $k_p\propto\sqrt{m_A}/R$ with a fitted coefficient $C_{\rm fit}\sim0.5$–$1$. The resulting density-fluctuation peak lies above the quantum Jeans wavenumber for $f_A\lesssim6\times10^{10}$ GeV, so gravitational collapse into miniclusters is strongly affected by quantum pressure. The paper argues that this convergence is robust for $f_A\lesssim2\times10^{10}$ GeV and may extend to $f_A\sim5.7\times10^{10}$ GeV; at larger $f_A$ self-interactions are too weak to erase the initial conditions, leaving observable memory of the misalignment landscape.

Load-bearing premise

The late-time conclusion rests on the assumption that the 'fattening' regulator used in the non-relativistic simulations—replacing the axion mass by a lattice-scale value only in the potential to halt wave collapse—does not bias the drift of the physical spectral peak, and that the small $256^3$ boxes resolve the relevant ultraviolet dynamics.

Editorial extensions

If this is right

  • For $f_A\lesssim2\times10^{10}$ GeV, the spectra from kinetic misalignment and post-inflationary axions coincide at matter–radiation equality, so minicluster and axion-star observations cannot distinguish the two production histories.
  • The velocity-dependent dilution factor $D(v)\sim0.2$–$0.3$ means homogeneous estimates overpredict the axion relic density by up to a factor of about four, and for $2.15\times10^{10}\lesssim f_A/\mathrm{GeV}\lesssim2.48\times10^{10}$ two different velocities reproduce the observed abundance.
  • For $f_A\lesssim6\times10^{10}$ GeV the density-fluctuation peak lies above the quantum Jeans scale, so gravitational collapse into miniclusters is delayed and central densities are lowered relative to the standard matter–radiation-equality collapse.
  • At larger $f_A$ (roughly above $5.7\times10^{10}$ GeV) self-interactions decouple before erasing the history, so the initial angle and velocity remain observable and different misalignment histories can produce different small-scale structures.

Reading between the lines

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

  • If the attractor is robust, axion small-scale structure becomes a function of $(f_A,\Omega_A)$ alone; one could then derive the minicluster mass function directly from the attractor spectrum and translate any null detection of miniclusters into a constraint on $f_A$ independent of the production mechanism.
  • The summit-landing instability is a finite-time hilltop effect; applying the same lattice pipeline to axion-like particles with different temperature-dependent masses (different exponent $n$ and crossover timing) would predict which mass ranges retain initial-condition memory, a parameter scan the paper does not perform.
  • Because the FAT regulator is ad hoc, a natural extension is to compare the extracted peak against an independent relativistic simulation that resolves axiton collapse for one representative $f_A$, checking explicitly whether the two-component dense-axion-star subtraction is unbiased.
Share X Bluesky LinkedIn Reddit HN

Signed reviews

No signed human review yet.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Referee Report

5 major / 5 minor

Summary. This Letter studies the nonlinear fate of pre-inflationary QCD axion dark matter in kinetic misalignment, treating the initial condition as a two-dimensional landscape in the initial angle Θ1 and velocity v. After mapping the zero-mode abundance and identifying a continuum of 'summit-landing' solutions, the authors perform large 3D relativistic lattice simulations of fragmentation for v≳100 and then switch to non-relativistic Gross-Pitaevskii simulations with a 'fattening' (FAT) regulator to follow the spectral peak through the QCD crossover toward matter-radiation equality. Their central claim is that for fA below about 2×10^10 GeV, strong self-interactions erase the early-history memory and drive the small-scale spectrum to the same attractor previously found for post-inflationary axions, with the peak position at matter-radiation equality determined only by fA and ΩA; this may extend to fA~5.7×10^10 GeV. The paper also reports that fragmentation reduces the comoving axion number by a velocity-dependent dilution factor D(v) and calibrates the velocity needed to reproduce the observed relic density.

Significance. If the central claim holds, the paper is significant: it would imply that kinetic misalignment and post-inflationary axion production produce equivalent small-scale dark matter structure for a wide range of axion masses, directly affecting minicluster and axion-star predictions. The work is also valuable for its extensive 3D simulations, explicit falsifiable scaling relations, and publicly available analysis tools in the companion repositories. The fragmentation dilution factor is supported by an independent lattice study, and the paper is commendably explicit about several numerical limitations. However, the central amnesia claim rests on the non-relativistic continuation of the peak drift, and that continuation depends on a fitted coefficient and an ad hoc regulator, so the significance is conditional on resolving the concerns below.

major comments (5)
  1. [§4, Eq. (4)] The predicted peak drift is not parameter-free. The text states that Eq. (4) is multiplied by a free coefficient Cfit and fitted to the late relativistic peak evolution (Cfit~0.5–1), so the reported agreement between the model and the relativistic simulations is partly by construction. Moreover, the NR runs are initialized with a spectrum peaked at the value extrapolated from the same linear/√(mA/R) model, so their subsequent evolution is not an independent test of the drift law. Please provide a posterior predictive check with Cfit fixed by the scattering calculation, or show explicitly how the attractor conclusion depends on the fitted coefficient.
  2. [Supplemental Eq. (S128) and Fig. S9] The FAT regulator replaces mψ only in the resummed Bessel potential, creating dense-axion-star (DAS) configurations at the grid scale, and the physical peak kNp is not measured directly: it is extracted from a two-component fit that subtracts a Gaussian DAS peak. The Supplemental Material itself concedes that the finite width of the DAS mass distribution can shift the extracted peak and that the regulator is not unique. All 15 runs per fA share the same FAT class and the same fitting procedure, so run-to-run stability cannot exclude a common bias; with N=256^3 the ultraviolet modes feeding the drift are only marginally resolved. A regulator-induced shift of even ~30% in kNp would materially change the comparison with Ref. [24], whose exponent is fA^-0.5 while this work finds fA^-0.73. Please validate the drift with an alternative regulator or a direct peak measurement without DAS subtraction.
  3. [Supplemental Material, summit-landing section (text after Fig. S4)] The paper explicitly states that for velocities leading to ρ0/ρ≲0.1 no clear convergence of ΩAh2 at η≳4η1 was found with feasible L and N, and that the quoted values 'potentially involve huge uncertainties.' This non-convergence weakens the treatment of the summit-landing branch, which is nevertheless presented as part of the misalignment landscape in Fig. 1 and used in the Discussion to argue that both Θ1 and v matter. The summit-landing power spectra in Fig. S6 also show features that depend on simulation parameters. The quantitative claims about this branch are therefore not supported by the present simulations.
  4. [Supplemental Eqs. (S110)–(S112) and Table S2] The dilution factor D(v) is a six-parameter fit to simulations at only two values of fA, and the quoted uncertainties are statistical only. This fit is then used to set the initial velocities of the large-scale runs whose spectra determine the attractor and the fA range over which amnesia holds. A systematic bias in D(v) would propagate into the initial velocities and hence into the reported kNp(fA) relation. Please quantify the systematic error, for example by varying the fit form and by including the independent lattice results of Ref. [51] in the calibration.
  5. [Discussion, comparison with Ref. [24]] The claimed equivalence to the post-inflationary attractor is not quantitatively demonstrated. The paper quotes kNp/kJ ~ 1.78(10^10 GeV/fA)^0.73 while Ref. [24] gives ~(10^10 GeV/fA)^0.5; these differ by a factor of order fA^0.23, which is about a factor 3 over the plotted decade. Given that this exponent is the quantitative basis for the statement that the spectra are 'equivalent within the uncertainties', the mismatch should be addressed explicitly, and the uncertainty on the exponent should be propagated into the conclusion.
minor comments (5)
  1. [Fig. 2 caption] The symbol PΘ is used in the figure but defined only through Eq. (S39); please define it directly in the caption as the integrated tail probability over initial angles.
  2. [Main text, Eq. (2)] The displayed exponents in Eq. (2) are typeset ambiguously (e.g., 'n+6 n+4'); please follow the notation of Supplemental Eq. (S21) to make the formula readable.
  3. [Fig. 4 caption] The phrase 'over the theory model∼√mA/R' is incomplete; please specify which curves correspond to the √(mA/R) prediction and which to the linear approximation.
  4. [Supplemental Eq. (S110)] The fitted sigmoid has a very steep slope n=20.0(9); a plot of the fit together with the residuals, or an alternative fit form, would help the reader judge the robustness of D(v).
  5. [Discussion] The text says 'for fA > 5×10^9 GeV, where Ref. [24] reports results', but the comparison in Fig. S13 appears to rely on an extrapolation of Ref. [24]; please clarify the fA range in which the comparison is direct rather than extrapolated.

Circularity Check

1 steps flagged · score 5.0 of 10

The late-time peak 'prediction' is amplitude-fitted and seeds the NR runs, so the attractor plateau is partly constructed; external Ref. [24] comparison keeps the claim from being fully circular.

  1. fitted input called prediction [Main text, 'Peak Drift from Self-Interactions' (Eq. 4, Fig. 4); Supplemental Material, 'Non-relativistic Evolution'.]
    "Since Eq. (4) can only be correct up to O(1) factors from the spectral shape and the peak drift efficiency, we multiply the prediction by a free coefficient kNp = Cfitkpred p and fit it to the late relativistic evolution, finding Cfit∼0.5−1, as expected. ... The Υ simulations start when all modes are safely non-relativistic, with a spectrum peaked at the kp extrapolated linearly from the relativistic peak drift model."

    The curve presented as a prediction is normalized with Cfit fitted to the very peak it is later used to predict, and the same fitted extrapolation sets the initial peak of the NR runs. The reported plateau kNp(ηc→ηeq) therefore starts from the fitted model value and evolves only mildly, so the 'agreement' in Fig. 4 and the attractor amplitude are partly by construction. The time dependence and the fA scaling are not fitted, and the comparison with Ref. [24] is external, so the circularity is partial rather than total.

full rationale

The paper is largely self-contained: the zero-mode abundance is derived from WKB and lattice QCD inputs; the dilution factor D(v) is presented as an explicit calibration rather than a hidden fit; and the central attractor comparison is made against the external post-inflationary simulations of Ref. [24], whose authors do not overlap with the present paper. The main circular element is the normalization of Eq. (4): Cfit is fitted to the late relativistic peak, and the same model extrapolation seeds the initial spectra of the non-relativistic runs, so the late-time plateau inherits the fitted amplitude. The Supplemental Material's admission that 'the finite width of the DAS mass distribution can shift the extracted peak' is a numerical robustness concern rather than a definitional circularity; if the FAT regulator biases kNp it would threaten the attractor claim, but that is a correctness risk, not a reduction of the derivation to its inputs. Since the scaling exponents and the external Ref. [24] comparison provide independent content, the overall circularity score is moderate.

Assumptions & free parameters 4 free parameters · 4 assumptions · 0 invented entities

The central claims rest on standard axion cosmology inputs (χ(T), Ω_c h^2, adiabatic seed), two fitted calibration sets (D(v) and Cfit), and one ad hoc numerical regulator (FAT). No new physical entities are postulated; axitons and dense axion stars are known objects from prior literature.

free parameters (4)
  • D(v) fit parameters = v0=137.7(4), n=20.0(9), A=0.65(1), v1=170.7(2), B=0.548(2), α=0.0834(6)
    Functional form Eq. (S110) fitted to the 3D dilution factors from simulations with fA = 10^9 and 10^10 GeV; used to compute the relic-density line and the double-valued region in Fig. 2.
  • Cfit = ~0.5-1
    Free O(1) coefficient multiplying the peak-drift prediction in Eq. (4); fitted to the late relativistic simulation peak evolution, so the reported agreement between model and simulation is partly calibrated.
  • Axiton masking parameters = cthres=100, rmask=6
    Threshold and mask radius for removing axiton cores from power spectra; chosen after testing several values, and the spectra in Fig. S8 depend on the masking choice.
  • NR fattening parameter µ_fat = 2.0, 2.2, 2.5, 2.7, 3.0
    FAT regulator in the non-relativistic Bessel potential (Eq. S128); varied across runs but is an ad hoc numerical scale that controls the artificial dense-axion-star population.
assumptions (4)
  • domain assumption QCD topological susceptibility χ(T) and thermal degrees of freedom from lattice QCD [30], matched to chiral perturbation theory and extrapolated as T^-8.16 beyond the lattice range.
    Sets the axion mass and background expansion; standard input from prior lattice results.
  • domain assumption Radiation domination with standard FLRW background and adiabatic initial conditions from the inflaton, extrapolated from CMB scales to the small scales k1 with As = 2.1e-9 and ns = 0.965, neglecting isocurvature fluctuations.
    The entire simulation program assumes this cosmological background and seed spectrum; isocurvature is explicitly neglected as strongly constrained.
  • domain assumption The initial fluctuation spectrum is cut off at k = 10^5 k*, the maximal kination duration Rs/Rkin ~ 10^5 allowed by the perturbative treatment in Ref. [21].
    Modes above the cutoff depend on pre-kination history; the maximal cutoff is used and the unamplified seed contributes at most about 2e-2 of the abundance along the CDM line.
  • ad hoc to paper The non-relativistic Gross-Pitaevskii description with the FAT regulator, an unphysically small susceptibility in the Bessel potential, captures the physical spectral drift.
    This regulator is introduced to prevent wave collapse from reaching unresolved scales; its effect on the peak drift is tested, but it is not a physically motivated parameter and could bias the measured peak.

how reviews work

0 comments
Cite this review

Pith. "Pith review of Amnesia in the Axion Misalignment Landscape." pith.science (2026). https://pith.science/paper/KLKTAO7B

@misc{pith2026260804139,
  author       = {Pith},
  title        = {Pith review of: Amnesia in the Axion Misalignment Landscape},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/KLKTAO7B}},
  note         = {Machine review of arXiv:2608.04139}
}
read the original abstract

Pre-inflationary axion cosmologies admit a broad range of initial velocities and angles that generate a landscape of misalignment histories, whose nonlinear fate and small-scale structure remain uncertain. We use lattice simulations to follow the QCD axion in the kinetic misalignment scenario through the QCD crossover into the non-relativistic regime, towards matter-radiation equality. In the meV mass range, this landscape contains a continuum of ''summit-landing" solutions sensitive to both the initial angle and velocity. Nonlinear fragmentation reduces the comoving axion number and modifies the relation between the misalignment history and present relic abundance. For sufficiently large axion masses, strong self-interactions drive the small-scale spectrum towards the attractor found for post-inflationary axions, so that distinct early histories can lead to similar late-time structures.

Figures

Figures reproduced from arXiv: 2608.04139 by the authors.

Figure 1
Figure 1. FIG. 1 [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 3
Figure 3. FIG. 3 [PITH_FULL_IMAGE:figures/full_fig_p003_3.png] view at source ↗
Figure 4
Figure 4. FIG. 4 [PITH_FULL_IMAGE:figures/full_fig_p004_4.png] view at source ↗
Figures from the paper (1 more)
Figure 5
Figure 5. Figure 5: FIG. 5 [PITH_FULL_IMAGE:figures/full_fig_p005_5.png]

Discussion (0). Continue with ORCID to comment.

Reference graph

Works this paper leans on

97 extracted references · 4 canonical work pages

  1. [24]

    and Hall, Lawrence J

    Co, Raymond T. and Hall, Lawrence J. and Harigaya, Keisuke. Axion Kinetic Misalignment Mechanism. Phys. Rev. Lett. 2020. doi:10.1103/PhysRevLett.124.251802. arXiv:1910.14152

    arXiv 2020

  2. [51]

    The spectrum of axions in a scaling string network

    Correia, Jos \'e and Hindmarsh, Mark and Lizarraga, Joanes and Lopez-Eiguren, Asier and Rummukainen, Kari and Urrestilla, Jon. The spectrum of axions in a scaling string network. 2025. arXiv:2512.13653

    arXiv 2025

  3. [1]

    jaxions : Simulating the Axion Dark Matter Field in the Post-Inflationary Scenario

    Vaquero, Alejandro and Redondo, Javier and Kaltschmidt, Mathieu and Pierobon, Giovanni and Saikawa, Ken'ichi. jaxions : Simulating the Axion Dark Matter Field in the Post-Inflationary Scenario. 2026

    2026

  4. [2]

    and others

    Arza, A. and others. The COSMIC WISPers White Paper: The physics case for Weakly Interacting Slim Particles. 2026. arXiv:2603.03433

    arXiv 2026

  5. [3]

    Axions at the meV crossroads: theory, cosmology, astrophysics, and experiments

    Cicoli, Michele and others. Axions at the meV crossroads: theory, cosmology, astrophysics, and experiments. JCAP. 2026. doi:10.1088/1475-7516/2026/07/060. arXiv:2603.18167

    arXiv 2026

  6. [4]

    Spectrum of global string networks and the axion dark matter mass

    Saikawa, Ken'ichi and Redondo, Javier and Vaquero, Alejandro and Kaltschmidt, Mathieu. Spectrum of global string networks and the axion dark matter mass. JCAP. 2024. doi:10.1088/1475-7516/2024/10/043. arXiv:2401.17253

    arXiv 2024

  7. [5]

    1988 , issn =

    Axion miniclusters , journal =. 1988 , issn =. doi:https://doi.org/10.1016/0370-2693(88)91655-3 , url =

    doi:10.1016/0370-2693(88)91655-3 1988

  8. [6]

    and Tkachev, Igor I

    Kolb, Edward W. and Tkachev, Igor I. , year=. Axion miniclusters and Bose stars , volume=. Physical Review Letters , publisher=. doi:10.1103/physrevlett.71.3051 , number=

    doi:10.1103/physrevlett.71.3051

Show all 97 references
  1. [7]

    Early seeds of axion miniclusters

    Vaquero, Alejandro and Redondo, Javier and Stadler, Julia. Early seeds of axion miniclusters. JCAP. 2019. doi:10.1088/1475-7516/2019/04/012. arXiv:1809.09241

    2019 arXiv

  2. [8]

    Eggemeier, Benedikt and O'Hare, Ciaran A. J. and Pierobon, Giovanni and Redondo, Javier and Wong, Yvonne Y. Y. Axion minivoids and implications for direct detection. Phys. Rev. D. 2023. doi:10.1103/PhysRevD.107.083510. arXiv:2212.00560

    2023 arXiv

  3. [9]

    Miniclusters from axion string simulations

    Pierobon, Giovanni and Redondo, Javier and Saikawa, Ken'ichi and Vaquero, Alejandro and Moore, Guy D. Miniclusters from axion string simulations. JCAP. 2026. doi:10.1088/1475-7516/2026/05/060. arXiv:2307.09941

    2026 arXiv

  4. [10]

    O'Hare, Ciaran A. J. and Pierobon, Giovanni and Redondo, Javier. Axion Minicluster Streams in the Solar Neighborhood. Phys. Rev. Lett. 2024. doi:10.1103/PhysRevLett.133.081001. arXiv:2311.17367

    2024 arXiv

  5. [11]

    Peccei, R. D. and Quinn, Helen R. CP Conservation in the Presence of Instantons. Phys. Rev. Lett. 1977. doi:10.1103/PhysRevLett.38.1440

    1977 doi

  6. [12]

    Peccei, R. D. and Quinn, Helen R. Constraints Imposed by CP Conservation in the Presence of Instantons. Phys. Rev. 1977. doi:10.1103/PhysRevD.16.1791

    1977 doi

  7. [13]

    A New Light Boson?

    Weinberg, Steven. A New Light Boson?. Phys. Rev. Lett. 1978. doi:10.1103/PhysRevLett.40.223

    1978 doi

  8. [14]

    Problem of Strong P and T Invariance in the Presence of Instantons

    Wilczek, Frank. Problem of Strong P and T Invariance in the Presence of Instantons. Phys. Rev. Lett. 1978. doi:10.1103/PhysRevLett.40.279

    1978 doi

  9. [15]

    and Wilczek, Frank

    Preskill, John and Wise, Mark B. and Wilczek, Frank. Cosmology of the Invisible Axion. Phys. Lett. 1983. doi:10.1016/0370-2693(83)90637-8

    1983 doi

  10. [16]

    Abbott, L. F. and Sikivie, P. A Cosmological Bound on the Invisible Axion. Phys. Lett. 1983. doi:10.1016/0370-2693(83)90638-X

    1983 doi

  11. [17]

    The Not So Harmless Axion

    Dine, Michael and Fischler, Willy. The Not So Harmless Axion. Phys. Lett. 1983. doi:10.1016/0370-2693(83)90639-1

    1983 doi

  12. [18]

    Axion Cosmology

    Sikivie, Pierre. Axion Cosmology. Lect. Notes Phys. 2008. doi:10.1007/978-3-540-73518-2_2. arXiv:astro-ph/0610440

    2008 arXiv

  13. [19]

    Marsh, David J. E. Axion Cosmology. Phys. Rept. 2016. doi:10.1016/j.physrep.2016.06.005. arXiv:1510.07633

    2016 arXiv

  14. [20]

    and Irastorza, Igor G

    Graham, Peter W. and Irastorza, Igor G. and Lamoreaux, Steven K. and Lindner, Axel and van Bibber, Karl A. Experimental Searches for the Axion and Axion-Like Particles. Ann. Rev. Nucl. Part. Sci. 2015. doi:10.1146/annurev-nucl-102014-022120. arXiv:1602.00039

    2015 arXiv

  15. [21]

    and Redondo, Javier

    Irastorza, Igor G. and Redondo, Javier. New experimental approaches in the search for axion-like particles. Prog. Part. Nucl. Phys. 2018. doi:10.1016/j.ppnp.2018.05.003. arXiv:1801.08127

    2018 arXiv

  16. [22]

    2011 , bdsk-url-1 =

    JCAP , pages =. 2011 , bdsk-url-1 =. doi:10.1088/1475-7516/2011/06/013 , eprint =

    2011 doi

  17. [23]

    2019 , bdsk-url-1 =

    JCAP , pages =. 2019 , bdsk-url-1 =. doi:10.1088/1475-7516/2019/06/047 , eprint =

    2019 doi

  18. [25]

    New Perspectives on Axion Misalignment Mechanism

    Chang, Chia-Feng and Cui, Yanou. New Perspectives on Axion Misalignment Mechanism. Phys. Rev. D. 2020. doi:10.1103/PhysRevD.102.015003. arXiv:1911.11885

    2020 arXiv

  19. [26]

    and Hall, Lawrence J

    Co, Raymond T. and Hall, Lawrence J. and Harigaya, Keisuke. QCD Axion Dark Matter with a Small Decay Constant. Phys. Rev. Lett. 2018. doi:10.1103/PhysRevLett.120.211602. arXiv:1711.10486

    2018 arXiv

  20. [27]

    and Hall, Lawrence J

    Co, Raymond T. and Hall, Lawrence J. and Harigaya, Keisuke and Olive, Keith A. and Verner, Sarunas. Axion Kinetic Misalignment and Parametric Resonance from Inflation. JCAP. 2020. doi:10.1088/1475-7516/2020/08/036. arXiv:2004.00629

    2020 arXiv

  21. [28]

    and Gonzalez, Eric and Harigaya, Keisuke

    Co, Raymond T. and Gonzalez, Eric and Harigaya, Keisuke. Axion Misalignment Driven to the Hilltop. JHEP. 2019. doi:10.1007/JHEP05(2019)163. arXiv:1812.11192

    2019 arXiv

  22. [29]

    and Gonzalez, Eric and Harigaya, Keisuke

    Co, Raymond T. and Gonzalez, Eric and Harigaya, Keisuke. Axion Misalignment Driven to the Bottom. JHEP. 2019. doi:10.1007/JHEP05(2019)162. arXiv:1812.11186

    2019 arXiv

  23. [30]

    and Ghalsasi, Akshay and Harigaya, Keisuke and Wang, Lian-Tao

    Bodas, Arushi and Co, Raymond T. and Ghalsasi, Akshay and Harigaya, Keisuke and Wang, Lian-Tao. Acoustic misalignment mechanism for axion dark matter. JHEP. 2025. doi:10.1007/JHEP08(2025)131. arXiv:2503.04888

    2025

  24. [31]

    Model implementations of axion dark matter from kinetic misalignment

    Er. Model implementations of axion dark matter from kinetic misalignment. JCAP. 2025. doi:10.1088/1475-7516/2025/08/087. arXiv:2408.08355

    2025 arXiv

  25. [32]

    ALP dark matter from kinetic fragmentation: opening up the parameter window

    Er\"oncel, Cem and Sato, Ryosuke and Servant, Geraldine and S. ALP dark matter from kinetic fragmentation: opening up the parameter window. JCAP. 2022. doi:10.1088/1475-7516/2022/10/053. arXiv:2206.14259

    2022 arXiv

  26. [33]

    Axion production via trapped misalignment from Peccei-Quinn symmetry breaking

    Di Luzio, Luca and S rensen, Philip. Axion production via trapped misalignment from Peccei-Quinn symmetry breaking. JHEP. 2024. doi:10.1007/JHEP10(2024)239. arXiv:2408.04623

    2024 arXiv

  27. [34]

    New Source for QCD Axion Dark Matter Production: Curvature Induced

    Er. New Source for QCD Axion Dark Matter Production: Curvature Induced. Phys. Rev. Lett. 2025. doi:10.1103/s3t7-41t2. arXiv:2503.04880

    2025

  28. [35]

    and Seong, Myeong-Jung and Song, Jun-Ho

    Lee, Hyun Min and Menkara, Adriana G. and Seong, Myeong-Jung and Song, Jun-Ho. Inflation models with Peccei Quinn symmetry and axion kinetic misalignment. Eur. Phys. J. C. 2024. doi:10.1140/epjc/s10052-024-13648-y. arXiv:2408.17013

    2024 arXiv

  29. [36]

    and Seong, Myeong-Jung and Song, Jun-Ho

    Lee, Hyun Min and Menkara, Adriana G. and Seong, Myeong-Jung and Song, Jun-Ho. Peccei-Quinn inflation at the pole and axion kinetic misalignment. JHEP. 2024. doi:10.1007/JHEP05(2024)295. arXiv:2310.17710

    2024 arXiv

  30. [37]

    oncel, Cem and Servant, G\'eraldine , title =

    Er\"oncel, Cem and Servant, G\'eraldine , title = ". JCAP. 2023. doi:10.1088/1475-7516/2023/01/009. arXiv:2207.10111

    2023 arXiv

  31. [38]

    QCD Axion Kinetic Misalignment without Prejudice

    Barman, Basabendu and Bernal, Nicol\'as and Ramberg, Nicklas and Visinelli, Luca. QCD Axion Kinetic Misalignment without Prejudice. Universe. 2022. doi:10.3390/universe8120634. arXiv:2111.03677

    2022 arXiv

  32. [39]

    and Dunsky, David and Fernandez, Nicolas and Ghalsasi, Akshay and Hall, Lawrence J

    Co, Raymond T. and Dunsky, David and Fernandez, Nicolas and Ghalsasi, Akshay and Hall, Lawrence J. and Harigaya, Keisuke and Shelton, Jessie. Gravitational wave and CMB probes of axion kination. JHEP. 2022. doi:10.1007/JHEP09(2022)116. arXiv:2108.09299

    2022 arXiv

  33. [40]

    Revealing the Primordial Irreducible Inflationary Gravitational-Wave Background with a Spinning Peccei-Quinn Axion

    Gouttenoire, Yann and Servant, G\'eraldine and Simakachorn, Peera. Revealing the Primordial Irreducible Inflationary Gravitational-Wave Background with a Spinning Peccei-Quinn Axion. 2021. arXiv:2108.10328

    2021 arXiv

  34. [41]

    Dark matter from an even lighter QCD axion: trapped misalignment

    Di Luzio, Luca and Gavela, Belen and Quilez, Pablo and Ringwald, Andreas. Dark matter from an even lighter QCD axion: trapped misalignment. JCAP. 2021. doi:10.1088/1475-7516/2021/10/001. arXiv:2102.01082

    2021 arXiv

  35. [42]

    and Tkachev, Igor I

    Kolb, Edward W. and Tkachev, Igor I. Nonlinear axion dynamics and formation of cosmological pseudosolitons. Phys. Rev. D. 1994. doi:10.1103/PhysRevD.49.5040. arXiv:astro-ph/9311037

    1994 arXiv

  36. [43]

    and Buschmann, Malte and Foster, Joshua W

    Benabou, Joshua N. and Buschmann, Malte and Foster, Joshua W. and Safdi, Benjamin R. Axion Mass Prediction from Adaptive Mesh Refinement Cosmological Lattice Simulations. Phys. Rev. Lett. 2025. doi:10.1103/6v21-d6sj. arXiv:2412.08699

    2025 arXiv

  37. [44]

    and Hook, Anson and Peterson, Adam and Willcox, Don E

    Buschmann, Malte and Foster, Joshua W. and Hook, Anson and Peterson, Adam and Willcox, Don E. and Zhang, Weiqun and Safdi, Benjamin R. Dark matter from axion strings with adaptive mesh refinement. Nature Commun. 2022. doi:10.1038/s41467-022-28669-y. arXiv:2108.05368

    2022 arXiv

  38. [45]

    and Safdi, Benjamin R

    Buschmann, Malte and Foster, Joshua W. and Safdi, Benjamin R. Early-Universe Simulations of the Cosmological Axion. Phys. Rev. Lett. 2020. doi:10.1103/PhysRevLett.124.161103. arXiv:1906.00967

    2020 arXiv

  39. [46]

    Axions from Strings: the Attractive Solution

    Gorghetto, Marco and Hardy, Edward and Villadoro, Giovanni. Axions from Strings: the Attractive Solution. JHEP. 2018. doi:10.1007/JHEP07(2018)151. arXiv:1806.04677

    2018 arXiv

  40. [47]

    More axions from strings

    Gorghetto, Marco and Hardy, Edward and Villadoro, Giovanni. More axions from strings. SciPost Phys. 2021. doi:10.21468/SciPostPhys.10.2.050. arXiv:2007.04990

    2021 arXiv

  41. [48]

    Axion dark matter from cosmic string network

    Kim, Heejoo and Park, Junghyeon and Son, Minho. Axion dark matter from cosmic string network. JHEP. 2024. doi:10.1007/JHEP07(2024)150. arXiv:2402.00741

    2024 arXiv

  42. [49]

    More scalings from cosmic strings

    Kim, Heejoo and Son, Minho. More scalings from cosmic strings. JHEP. 2025. doi:10.1007/JHEP07(2025)052. arXiv:2411.08455

    2025

  43. [50]

    Scaling density of axion strings in terasite simulations

    Correia, Jos\'e and Hindmarsh, Mark and Lizarraga, Joanes and Lopez-Eiguren, Asier and Rummukainen, Kari and Urrestilla, Jon. Scaling density of axion strings in terasite simulations. Phys. Rev. D. 2025. doi:10.1103/PhysRevD.111.063532. arXiv:2410.18064

    2025 arXiv

  44. [52]

    Axion dark matter: strings and their cores

    Fleury, Leesa and Moore, Guy D. Axion dark matter: strings and their cores. JCAP. 2016. doi:10.1088/1475-7516/2016/01/004. arXiv:1509.00026

    2016 arXiv

  45. [53]

    Kinetic fragmentation of the QCD axion on the lattice

    Fasiello, Matteo and Lizarraga, Joanes and Papageorgiou, Alexandros and Urio, Ander. Kinetic fragmentation of the QCD axion on the lattice. JCAP. 2025. doi:10.1088/1475-7516/2025/09/019. arXiv:2507.01822

    2025

  46. [54]

    and Van Tilburg, Ken

    Arvanitaki, Asimina and Dimopoulos, Savas and Galanis, Marios and Lehner, Luis and Thompson, Jedidiah O. and Van Tilburg, Ken. Large-misalignment mechanism for the formation of compact axion structures: Signatures from the QCD axion to fuzzy dark matter. Phys. Rev. D. 2020. do...

    2020 arXiv

  47. [56]

    2016 , bdsk-url-1 =

    Nature , number =. 2016 , bdsk-url-1 =. doi:10.1038/nature20115 , eprint =

    2016 doi

  48. [57]

    2014 , bdsk-url-1 =

    JINST , pages =. 2014 , bdsk-url-1 =. doi:10.1088/1748-0221/9/05/T05002 , eprint =

    2014 doi

  49. [58]

    Phys. Rev. D , pages =. 2011 , bdsk-url-1 =. doi:10.1103/PhysRevD.84.103008 , eprint =

    2011 doi

  50. [59]

    doi:10.5281/zenodo.3932430 , howpublished =

    Ciaran O'Hare , title =. doi:10.5281/zenodo.3932430 , howpublished =

    doi

  51. [60]

    and Turner, Michael S

    Axenides, Minos and Brandenberger, Robert H. and Turner, Michael S. Development of Axion Perturbations in an Axion Dominated Universe. Phys. Lett. B. 1983. doi:10.1016/0370-2693(83)90586-5

    1983 doi

  52. [61]

    Resonant excitation of the axion field during the QCD phase transition

    Sikivie, Pierre and Xue, Wei. Resonant excitation of the axion field during the QCD phase transition. Phys. Rev. D. 2022. doi:10.1103/PhysRevD.105.043533. arXiv:2110.13157

    2022 arXiv

  53. [62]

    New scenario of QCD axion clump formation

    Kitajima, Naoya and Kogai, Kazuhiro and Urakawa, Yuko. New scenario of QCD axion clump formation. Part I. Linear analysis. JCAP. 2022. doi:10.1088/1475-7516/2022/03/039. arXiv:2111.05785

    2022 arXiv

  54. [63]

    and Chakraborty, Priyesh and Fan, JiJi and Reece, Matthew

    Allali, Itamar J. and Chakraborty, Priyesh and Fan, JiJi and Reece, Matthew. Axion Perturbations: A General Analytical Treatment. 2025. arXiv:2510.07371

    2025 arXiv

  55. [64]

    O'Hare, Ciaran A. J. Cosmology of axion dark matter. PoS. 2024. doi:10.22323/1.454.0040. arXiv:2403.17697

    2024 arXiv

  56. [65]

    and others

    Aghanim, N. and others. Planck 2018 results. VI. Cosmological parameters. Astron. Astrophys. 2020. doi:10.1051/0004-6361/201833910. arXiv:1807.06209

    2018 arXiv

  57. [66]

    and others

    Akrami, Y. and others. Planck 2018 results. X. Constraints on inflation. Astron. Astrophys. 2020. doi:10.1051/0004-6361/201833887. arXiv:1807.06211

    2018 arXiv

  58. [67]

    Isocurvature Constraints and Anharmonic Effects on QCD Axion Dark Matter

    Kobayashi, Takeshi and Kurematsu, Ryosuke and Takahashi, Fuminobu. Isocurvature Constraints and Anharmonic Effects on QCD Axion Dark Matter. JCAP. 2013. doi:10.1088/1475-7516/2013/09/032. arXiv:1304.0922

    2013 arXiv

  59. [68]

    Adame, A. G. and others. DESI 2024 VI: cosmological constraints from the measurements of baryon acoustic oscillations. JCAP. 2025. doi:10.1088/1475-7516/2025/02/021. arXiv:2404.03002

    2024 arXiv

  60. [69]

    and others

    Tristram, M. and others. Cosmological parameters derived from the final Planck data release (PR4). Astron. Astrophys. 2024. doi:10.1051/0004-6361/202348015. arXiv:2309.10034

    2024 arXiv

  61. [70]

    CMB power spectra and cosmological parameters from Planck PR4 with CamSpec

    Rosenberg, Erik and Gratton, Steven and Efstathiou, George. CMB power spectra and cosmological parameters from Planck PR4 with CamSpec. Mon. Not. Roy. Astron. Soc. 2022. doi:10.1093/mnras/stac2744. arXiv:2205.10869

    2022 arXiv

  62. [71]

    The Atacama Cosmology Telescope: DR4 Maps and Cosmological Parameters

    Aiola, Simone and others. The Atacama Cosmology Telescope: DR4 Maps and Cosmological Parameters. JCAP. 2020. doi:10.1088/1475-7516/2020/12/047. arXiv:2007.07288

    2020 arXiv

  63. [72]

    Abbott, T. M. C. and others. Dark Energy Survey Year 3 results: Cosmological constraints from galaxy clustering and weak lensing. Phys. Rev. D. 2022. doi:10.1103/PhysRevD.105.023520. arXiv:2105.13549

    2022 arXiv

  64. [73]

    Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Cosmological implications from two decades of spectroscopic surveys at the Apache Point Observatory

    Alam, Shadab and others. Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Cosmological implications from two decades of spectroscopic surveys at the Apache Point Observatory. Phys. Rev. D. 2021. doi:10.1103/PhysRevD.103.083533. arXiv:2007.08991

    2021 arXiv

  65. [74]

    Universal bound on QCD axions from supernovae

    Springmann, Konstantin and Stadlbauer, Michael and Stelzl, Stefan and Weiler, Andreas. Universal bound on QCD axions from supernovae. Phys. Rev. D. 2025. doi:10.1103/18t2-1w3b. arXiv:2410.19902

    2025 arXiv

  66. [75]

    Astrophysical Axion Bounds: The 2024 Edition

    Caputo, Andrea and Raffelt, Georg. Astrophysical Axion Bounds: The 2024 Edition. PoS. 2024. doi:10.22323/1.454.0041. arXiv:2401.13728

    2024 arXiv

  67. [76]

    Astrophysical axion bounds

    Raffelt, Georg G. Astrophysical axion bounds. Lect. Notes Phys. 2008. doi:10.1007/978-3-540-73518-2_3. arXiv:hep-ph/0611350

    2008 arXiv

  68. [77]

    Universal Bound on the Duration of a Kination Era

    Er. Universal Bound on the Duration of a Kination Era. Phys. Rev. Lett. 2025. doi:10.1103/k7ty-gwjg. arXiv:2501.17226

    2025

  69. [78]

    Searching for the QCD Dark Matter Axion

    Baryakhtar, Masha and Rosenberg, Leslie and Rybka, Gray. Searching for the QCD Dark Matter Axion. 2025. arXiv:2504.10607

    2025 arXiv

  70. [79]

    New Technologies for Axion and Dark Photon Searches

    Berlin, Asher and Kahn, Yonatan. New Technologies for Axion and Dark Photon Searches. Ann. Rev. Nucl. Part. Sci. 2025. doi:10.1146/annurev-nucl-121423-101015. arXiv:2412.08704

    2025 arXiv

  71. [80]

    Can axion clumps be formed in a pre-inflationary scenario?

    Fukunaga, Hayato and Kitajima, Naoya and Urakawa, Yuko. Can axion clumps be formed in a pre-inflationary scenario?. JCAP. 2021. doi:10.1088/1475-7516/2021/02/015. arXiv:2004.08929

    2021 arXiv

  72. [82]

    More axion stars from strings

    Gorghetto, Marco and Hardy, Edward and Villadoro, Giovanni. More axion stars from strings. JHEP. 2024. doi:10.1007/JHEP08(2024)126. arXiv:2405.19389

    2024 arXiv

  73. [83]

    From Rags to Jeans: Axion Miniclusters from Early matter domination

    Angulo, Ariel and Arias, Paola and Bernal, Nicol \'a s and Redondo, Javier. From Rags to Jeans: Axion Miniclusters from Early matter domination. 2026. arXiv:2606.19439

    2026 arXiv

  74. [84]

    and Jackson, G

    Escudero, M. and Jackson, G. and Laine, M. and Sandner, S. Fast and flexible neutrino decoupling. Part I. The Standard Model. JCAP. 2026. doi:10.1088/1475-7516/2026/02/046. arXiv:2511.04747

    2026

  75. [85]

    , keywords =

    The Temperature of the Cosmic Microwave Background. , keywords =. doi:10.1088/0004-637X/707/2/916 , archivePrefix =. 0911.1955 , primaryClass =

    1955 arXiv

  76. [86]

    The QCD axion, precisely

    Grilli di Cortona, Giovanni and Hardy, Edward and Pardo Vega, Javier and Villadoro, Giovanni. The QCD axion, precisely. JHEP. 2016. doi:10.1007/JHEP01(2016)034. arXiv:1511.02867

    2016 arXiv

  77. [87]

    Impact of adiabatic temperature fluctuations on the power spectrum of axion density perturbations

    Ayad, Ahmed and Schwarz, Dominik J. Impact of adiabatic temperature fluctuations on the power spectrum of axion density perturbations. JCAP. 2025. doi:10.1088/1475-7516/2025/08/073. arXiv:2503.05532

    2025 arXiv

  78. [88]

    Adiabatic modes in cosmology

    Weinberg, Steven. Adiabatic modes in cosmology. Phys. Rev. D. 2003. doi:10.1103/PhysRevD.67.123504. arXiv:astro-ph/0302326

    2003 arXiv

  79. [89]

    Dilute and dense axion stars

    Visinelli, Luca and Baum, Sebastian and Redondo, Javier and Freese, Katherine and Wilczek, Frank. Dilute and dense axion stars. Phys. Lett. B. 2018. doi:10.1016/j.physletb.2017.12.010. arXiv:1710.08910

    2018 arXiv

  80. [90]

    Levkov, D. G. and Panin, A. G. and Tkachev, I. I. Relativistic axions from collapsing Bose stars. Phys. Rev. Lett. 2017. doi:10.1103/PhysRevLett.118.011301. arXiv:1609.03611

    2017 arXiv

  81. [91]

    Dense Axion Stars

    Braaten, Eric and Mohapatra, Abhishek and Zhang, Hong. Dense Axion Stars. Phys. Rev. Lett. 2016. doi:10.1103/PhysRevLett.117.121801. arXiv:1512.00108

    2016 arXiv

  82. [92]

    Cosmic and Local Mass Density of Invisible Axions

    Turner, Michael S. Cosmic and Local Mass Density of Invisible Axions. Phys. Rev. D. 1986. doi:10.1103/PhysRevD.33.889

    1986 doi

  83. [93]

    WISPy Cold Dark Matter

    Arias, Paola and Cadamuro, Davide and Goodsell, Mark and Jaeckel, Joerg and Redondo, Javier and Ringwald, Andreas. WISPy Cold Dark Matter. JCAP. 2012. doi:10.1088/1475-7516/2012/06/013. arXiv:1201.5902

    2012 arXiv

  84. [94]

    Update of axion CDM energy

    Bae, Kyu Jung and Huh, Ji-Haeng and Kim, Jihn E. Update of axion CDM energy. JCAP. 2008. doi:10.1088/1475-7516/2008/09/005. arXiv:0806.0497

    2008 arXiv

  85. [95]

    Wantz, Olivier and Shellard, E. P. S. Axion Cosmology Revisited. Phys. Rev. D. 2010. doi:10.1103/PhysRevD.82.123508. arXiv:0910.1066

    2010 arXiv

  86. [96]

    Axion fragmentation

    Fonseca, Nayara and Morgante, Enrico and Sato, Ryosuke and Servant, G \'e raldine. Axion fragmentation. JHEP. 2020. doi:10.1007/JHEP04(2020)010. arXiv:1911.08472

    2020 arXiv

  87. [97]

    Pre-inflationary QCD axion stars after moduli domination

    Hardy, Edward and S \'a nchez Gonz \'a lez, Noelia and Stubbs, Henry and Tranchedone, Lorenzo. Pre-inflationary QCD axion stars after moduli domination. 2026. arXiv:2605.00103

    2026 arXiv

  88. [98]

    Axion fragmentation on the lattice

    Morgante, Enrico and Ratzinger, Wolfram and Sato, Ryosuke and Stefanek, Ben A. Axion fragmentation on the lattice. JHEP. 2021. doi:10.1007/JHEP12(2021)037. arXiv:2109.13823

    2021 arXiv

  89. [99]

    and Tkachev, I

    Kolb, Edward W. and Tkachev, I. I. Axitons. International Conference on Unified Symmetry - in the Small and in the Large. 1994. doi:10.1007/978-1-4615-1855-6_6

    1994 doi

Pith tools

Reviewed August 15, 2026 · model on record in the stance chip above.