REVIEW 4 minor 1 cited by
Large homogeneous data admit forward self-similar solutions for 2D hypodissipative Navier-Stokes, and they become smooth with sharp decay once the fractional power exceeds 2/3.
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 · grok-4.5
2026-07-14 22:17 UTC pith:V3AFF4TY
load-bearing objection Solid 2D fractional self-similar existence with sharp decay for every weak solution when α>2/3; numerics are honest evidence on a surrogate.
Forward Self-Similar Solutions to the 2D Hypodissipative Navier-Stokes Equations
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
For every alpha in (1/2,1) and every divergence-free (1-2alpha)-homogeneous initial datum that is locally Lipschitz, the self-similar profile equation admits a weak solution U = U0 + V with V in H^alpha; when alpha exceeds 2/3 every such weak solution is smooth and satisfies the sharp far-field bounds |nabla^k (U - U0)(x)| less than or equal to C (1+|x|)^{1-4alpha} (or with a logarithm when the data are only Lipschitz).
What carries the argument
Decomposition U = U0 + V together with a Bogovskii correction that truncates the background velocity so its gradient becomes arbitrarily small, allowing a coercive H^alpha energy estimate that feeds the Leray-Schauder fixed-point construction; regularity and decay are then recovered by mollification, weighted energy estimates, and a Duhamel representation that treats the nonlinear terms as a source.
Load-bearing premise
The uniform energy bound that makes the fixed-point argument work rests on being able to cut off the fractional-heat profile far away and restore divergence-free structure while keeping the gradient of the corrected field arbitrarily small; that step uses the known pointwise decay of the heat profile.
What would settle it
Either exhibit a large locally Lipschitz homogeneous datum for which no H^alpha weak self-similar profile exists, or produce a weak H^alpha solution for some alpha greater than 2/3 that fails to be smooth or that decays slower than the claimed rate (1+|x|)^{1-4alpha}.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper constructs forward self-similar solutions of the 2D hypodissipative Navier–Stokes system with fractional diffusion (−Δ)^α for α∈(1/2,1). For arbitrarily large divergence-free (1−2α)-homogeneous initial data that are locally Lipschitz, Theorem 1.1 / Theorem 3.1 produces at least one weak solution whose profile U satisfies U−U0∈H^α(R²), where U0 is the fractional-heat profile. For α∈(2/3,1) every such H^α weak solution is shown to be smooth (Proposition 4.1) and to obey the sharp pointwise decay estimates |∇^k(U−U0)(x)|≲(1+|x|)^{1−4α} (with a logarithmic loss for merely Lipschitz data). The argument proceeds by Leray–Schauder on approximating balls with vanishing viscosity, a Bogovskiĭ correction that makes the background gradient small, a-posteriori bootstrap via mollification and difference quotients, weighted energy estimates that preserve H^α-coercivity, and a Duhamel representation with an Oseen kernel. A final numerical section studies a related 2D Navier–Stokes equation with time-dependent viscosity and reports eigenvalue crossings and symmetry-breaking bifurcations for large k-fold-symmetric data.
Significance. The work supplies a complete existence–regularity–decay theory for large-data forward self-similar solutions of the 2D fractional Navier–Stokes equations down to the natural threshold α=1/2, with a clean smoothness threshold α=2/3 coming from the Sobolev product H^α×H^α↪H^{2α−1}. The pointwise far-field estimates are sharp (matching the source U0·∇U0) and hold for every H^α weak solution, not merely the constructed ones; this information is useful for future non-uniqueness arguments. The technical ingredients—Bogovskiĭ truncation of the background, carefully designed weights that retain coercivity, quantitative mollification commutators, and the multiplier trick that removes the logarithmic loss—are standard but carefully adapted to the fractional setting and yield a self-contained, non-circular proof. The numerical evidence for a surrogate equation is presented as exploratory and does not claim to prove non-uniqueness of the original system.
minor comments (4)
- In the statement of Theorem 1.1 the decay exponents for U itself and for U−U0 are written with the same constant C; it would help the reader if the dependence of C on the C^{m,β}-norm of the angular data were made explicit (as is done later in Lemma 2.1).
- Section 6 and Appendix B are independent of the analytic theorems; a short sentence at the beginning of §6 reminding the reader that the numerics concern only the surrogate equation (NSt,α) would prevent any possible misreading.
- A few typographical inconsistencies appear (e.g., “ˇSverák” vs “Sverak”, occasional missing spaces around operators). A light copy-edit pass would clean them up.
- Lemma 2.1 and the subsequent decay statements for the Oseen kernel (Lemma A.6) are used repeatedly; cross-references to the precise decay rates when they are invoked in §5 would improve readability.
Circularity Check
No significant circularity: existence, regularity upgrade, and decay estimates are derived from the equation via standard energy methods, Leray–Schauder, and Duhamel without fitted parameters or load-bearing self-citations that close a loop.
full rationale
The derivation chain is self-contained. U0 is the explicit fractional-heat profile (convolution against the heat kernel); its pointwise decay (Lemma 2.1) is obtained by Taylor expansion of the homogeneous data against the known kernel decay and is independent of the nonlinear problem. Existence of V ∈ H^α (Theorem 3.1) proceeds by adding artificial viscosity, localizing to balls, and applying Leray–Schauder to the compact continuous map T; the only non-routine step is a Bogovskiĭ correction that truncates U0 at large radius so that ∥∇U1∥_∞ can be made arbitrarily small and the transport term absorbed into the coercive H^α energy. That truncation is justified solely by the already-established decay of U0, not by any property of V. A-posteriori regularity for α > 2/3 (Proposition 4.1) uses quantitative mollification commutators and the Sobolev multiplication H^α × H^α ↪ H^{2α−1}; weighted estimates and the subsequent Duhamel bootstrap with the Oseen kernel recover the sharp source rate of U0·∇U0. No quantity is defined in terms of a later “prediction,” no uniqueness theorem is imported from the authors’ prior work to force the present construction, and the numerical section on the surrogate time-dependent-viscosity equation is explicitly labeled as independent evidence. Self-citations appear only as background comparisons and do not close any logical loop.
Axiom & Free-Parameter Ledger
free parameters (2)
- boundary amplitude σ
- computational radius R and mesh size h
axioms (4)
- standard math Sobolev multiplication H^α×H^α↪H^{2α−1} for α∈(1/2,1) and the resulting gain 4α−2>α precisely when α>2/3
- standard math Pointwise decay of the fractional heat kernel and of its derivatives (Lemma 2.1)
- standard math Existence and L^∞ bounds for the Bogovskiĭ operator on annular domains
- domain assumption The surrogate equation with time-dependent viscosity shares the same scaling and therefore the same self-similar profiles as the original fractional system
read the original abstract
We study the forward self-similar solutions to the $2$D hypodissipative Navier-Stokes equation with fractional diffusion $(-\Delta)^\alpha$ for $\frac{1}{2}<\alpha<1$. We first show that for arbitrarily large $(1-2\alpha)$-homogeneous initial data which are locally Lipschitz, there exists at least one weak solution whose profile differs from the self-similar profile of the fractional heat equation by an element of $H^\alpha(\reall^2)$. Moreover, when $\alpha\in(\frac{2}{3},1)$ we show that any such weak solution is actually smooth, hence a strong solution, and satisfies certain far field decay estimates. Finally, we provide numerical evidence for the nonuniqueness of the related $2$D Navier-Stokes equation with time-dependent viscosity.
Forward citations
Cited by 1 Pith paper
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Self-Similar Solutions of the Two-Dimensional Incompressible Euler Equation from Large Initial Data
For every C^1 divergence-free (−a)-homogeneous velocity on R^2, a self-similar 2D Euler weak solution with that initial profile exists for each a in (1/3,1).
Reference graph
Works this paper leans on
-
[1]
Global weak besov solutions of the navier–stokes equations and applications.������� ��� �������� ��������� ��� ��������, 232(1):197–263, Apr 2019
Dallas Albritton and Tobias Barker. Global weak besov solutions of the navier–stokes equations and applications.������� ��� �������� ��������� ��� ��������, 232(1):197–263, Apr 2019
2019
-
[2]
Non-uniqueness of Leray solutions of the forced Navier-Stokes equations.���� �� ����� ���, 196(1):415–455, 2022
Dallas Albritton, Elia Bru´ e, and Maria Colombo. Non-uniqueness of Leray solutions of the forced Navier-Stokes equations.���� �� ����� ���, 196(1):415–455, 2022
2022
-
[3]
Princeton University Press, 2024
Dallas Albritton, Elia Bru´ e, Maria Colombo, Camillo De Lellis, Vikram Giri, Maximilian Janisch, and Hyunju Kwon.����������� ��� �������������� ��� ��� �� ����� ���������� ����� �� ������� ���������, volume 215. Princeton University Press, 2024
2024
-
[4]
Non-uniqueness of Leray solutions to the hypodissipative Navier- Stokes equations in two dimensions.����� ����� �����, 402(1):429–446, 2023
Dallas Albritton and Maria Colombo. Non-uniqueness of Leray solutions to the hypodissipative Navier- Stokes equations in two dimensions.����� ����� �����, 402(1):429–446, 2023
2023
-
[5]
Vanishing viscosity non-unique solutions to the forced 2d euler equations, 2025
Dallas Albritton, Maria Colombo, and Giulia Mescolini. Vanishing viscosity non-unique solutions to the forced 2d euler equations, 2025. 50
2025
-
[6]
Forward self-similar solutions to the 2d navier–stokes equations, 2026
Dallas Albritton, Julien Guillod, Mikhail Korobkov, and Xiao Ren. Forward self-similar solutions to the 2d navier–stokes equations, 2026
2026
-
[7]
Baratta, Joseph P
Igor A. Baratta, Joseph P. Dean, Jørgen S. Dokken, Michal Habera, Jack S. Hale, Chris N. Richardson, Marie E. Rognes, Matthew W. Scroggs, Nathan Sime, and Garth N. Wells. DOLFINx: The next generation FEniCS problem solving environment, 2023
2023
-
[8]
Oscar A. Barraza. Self-similar solutions in weakL p-spaces of the Navier-Stokes equations.������� ������ ����� ��������������, 12(2):411–439, 1996
1996
-
[9]
Spatial decay of discretely self-similar solutions to the Navier– Stokes equations.���� ��� ������� ��������, 5(2):377–407, 2023
Zachary Bradshaw and Patrick Phelps. Spatial decay of discretely self-similar solutions to the Navier– Stokes equations.���� ��� ������� ��������, 5(2):377–407, 2023
2023
-
[10]
Forward discretely self-similar solutions of the Navier-Stokes equations II.���� ����� �������� �, 18(3):1095–1119, 2017
Zachary Bradshaw and Tai-Peng Tsai. Forward discretely self-similar solutions of the Navier-Stokes equations II.���� ����� �������� �, 18(3):1095–1119, 2017
2017
-
[11]
Rotationally corrected scaling invariant solutions to the Navier- Stokes equations.����� ������� ����������� ���������, 42(7):1065–1087, 2017
Zachary Bradshaw and Tai-Peng Tsai. Rotationally corrected scaling invariant solutions to the Navier- Stokes equations.����� ������� ����������� ���������, 42(7):1065–1087, 2017
2017
-
[12]
Discretely self-similar solutions to the navier–stokes equations with besov space data.������� ��� �������� ��������� ��� ��������, 229(1):53–77, Jul 2018
Zachary Bradshaw and Tai-Peng Tsai. Discretely self-similar solutions to the navier–stokes equations with besov space data.������� ��� �������� ��������� ��� ��������, 229(1):53–77, Jul 2018
2018
-
[13]
Discretely self-similar solutions to the navier–stokes equations with data inl 2 loc satisfying the local energy inequality.�������� � ���, 12(8):1943–1962, 2019
Zachary Bradshaw and Tai-Peng Tsai. Discretely self-similar solutions to the navier–stokes equations with data inl 2 loc satisfying the local energy inequality.�������� � ���, 12(8):1943–1962, 2019
1943
-
[14]
Cannone, Y
M. Cannone, Y. Meyer, and F. Planchon. Solutions auto-similaires des ´ equations de navier-stokes. �� ������������������ ��� �� ����� ��� ���������� ���������������, pages 1–10, 1993-1994
1993
-
[15]
Cannone and F Planchon
M. Cannone and F Planchon. Self-similar solutions for navier-stokes equations in.�������������� �� ������� ����������� ���������, 21(1-2):179–193, 1996
1996
-
[16]
Dongho Chae and J¨ org Wolf. Existence of discretely self-similar solutions to the navier–stokes equations for initial value in lloc2(r3).������� �� ���������� ����� �������� � �� ������� ��� ���� �����, 35(4):1019– 1039, 2018
2018
-
[17]
Jiajie Chen and Thomas Y. Hou. Stable nearly self-similar blowup of the 2d boussinesq and 3d euler equations with smooth data i: Analysis, 2023
2023
-
[18]
Jiajie Chen and Thomas Y. Hou. Stable nearly self-similar blowup of the 2d boussinesq and 3d euler equations with smooth data ii: Rigorous numerics.���������� �������� � ����������, 23(1):25–130, 2025
2025
-
[19]
Asymmetric self-similar spiral solutions of 2-d incomressible euler equations, 2025
Hyungjun Choi. Asymmetric self-similar spiral solutions of 2-d incomressible euler equations, 2025
2025
-
[20]
Ill-posedness of leray solutions for the hy- podissipative navier–stokes equations.�������������� �� ������������ �������, 362(2):659–688, Sep 2018
Maria Colombo, Camillo De Lellis, and Luigi De Rosa. Ill-posedness of leray solutions for the hy- podissipative navier–stokes equations.�������������� �� ������������ �������, 362(2):659–688, Sep 2018
2018
-
[21]
Optimal local smoothing and analyticity rate estimates for the generalized navier-stokes equations.�������������� �� ������������ ��������, 7:67–80, 2009
Hongjie Dong and Dong Li. Optimal local smoothing and analyticity rate estimates for the generalized navier-stokes equations.�������������� �� ������������ ��������, 7:67–80, 2009
2009
-
[22]
Tarek M. Elgindi. Finite-time singularity formation forC 1,α solutions to the incompressible Euler equations onR 3.������ �� �����������, 194(3):647 – 727, 2021
2021
-
[23]
Elgindi, Tej-Eddine Ghoul, and Nader Masmoudi
Tarek M. Elgindi, Tej-Eddine Ghoul, and Nader Masmoudi. On the stability of self-similar blow-up for c1,α solutions to the incompressible euler equations onR 3.��������� ������� �� �����������, 2019
2019
-
[24]
Algebraic spiral solutions of 2d incompressible euler.������� �� ����������� ���������, 255(11):3749–3787, 2013
Volker Elling. Algebraic spiral solutions of 2d incompressible euler.������� �� ����������� ���������, 255(11):3749–3787, 2013. 51
2013
-
[25]
Algebraic spiral solutions of the 2d incompressible euler equations.�������� �� ��� ��������� ������������ �������� ��� ������, 47(1):323–334, Mar 2016
Volker Elling. Algebraic spiral solutions of the 2d incompressible euler equations.�������� �� ��� ��������� ������������ �������� ��� ������, 47(1):323–334, Mar 2016
2016
-
[26]
Self-similar 2d euler solutions with mixed-sign vorticity.�������������� �� ������������ �������, 348(1):27–68, Nov 2016
Volker Elling. Self-similar 2d euler solutions with mixed-sign vorticity.�������������� �� ������������ �������, 348(1):27–68, Nov 2016
2016
-
[27]
Springer Monographs in Mathematics
Giovanni Paolo Galdi.�� ������������ �� ��� ������������ ������ �� ��� ������������� ���������� ������������ ��������. Springer Monographs in Mathematics. Springer New York, NY, 2 edition, 2011. XIV, 1018 pages
2011
-
[28]
Navier-stokes flow in r3 with measures as initial vorticity and morrey spaces.�������������� �� ������� ����������� ���������, 14(5):577–618, 1989
Yoshikazu Giga and Tetsuro Miyakawa. Navier-stokes flow in r3 with measures as initial vorticity and morrey spaces.�������������� �� ������� ����������� ���������, 14(5):577–618, 1989
1989
-
[29]
The kato-ponce inequality.�������������� �� ������� ����������� ���������, 39(6):1128–1157, 2014
Loukas Grafakos and Seungly Oh. The kato-ponce inequality.�������������� �� ������� ����������� ���������, 39(6):1128–1157, 2014
2014
-
[30]
On the forward self-similar solutions to the two-dimensional navier-stokes equations, 2026
Changfeng Gui, Hao Liu, and Chunjing Xie. On the forward self-similar solutions to the two-dimensional navier-stokes equations, 2026
2026
-
[31]
Numerical investigations of non-uniqueness for the navier–stokes initial value problem in borderline spaces.������� �� ������������ ����� ���������, 25(3):46, May 2023
Julien Guillod and Vladim´ ırˇSver´ ak. Numerical investigations of non-uniqueness for the navier–stokes initial value problem in borderline spaces.������� �� ������������ ����� ���������, 25(3):46, May 2023
2023
-
[32]
Roman, and Vicente Vidal
Vicente Hernandez, Jose E. Roman, and Vicente Vidal. SLEPc: A scalable and flexible toolkit for the solution of eigenvalue problems.��� ������������ �� ������������ ��������, 31(3):351–362, 2005
2005
-
[33]
Nonuniqueness of leray-hopf solutions to the unforced incompressible 3d navier-stokes equation, 2025
Thomas Hou, Yixuan Wang, and Changhe Yang. Nonuniqueness of leray-hopf solutions to the unforced incompressible 3d navier-stokes equation, 2025
2025
-
[34]
Thomas Y. Hou. Potentially singular behavior of the 3D Navier-Stokes equations.������ ������� �����, 23(6):2251–2299, 2023
2023
-
[35]
Hyt¨ onen
Tuomas P. Hyt¨ onen. The sharp weighted bound for general Calder´ on–Zygmund operators.������ �� �����������, 175(3):1473–1506, 2012
2012
-
[36]
Are the incompressible 3d navier–stokes equations locally ill-posed in the natural energy space?������� �� ���������� ��������, 268(12):3734–3766, 2015
Hao Jia and Vladimir Sverak. Are the incompressible 3d navier–stokes equations locally ill-posed in the natural energy space?������� �� ���������� ��������, 268(12):3734–3766, 2015
2015
-
[37]
Local-in-space estimates near initial time for weak solutions of the Navier-Stokes equations and forward self-similar solutions.������� �����, 196(1):233–265, 2014
Hao Jia and Vladim´ ır ˇSzver´ ak. Local-in-space estimates near initial time for weak solutions of the Navier-Stokes equations and forward self-similar solutions.������� �����, 196(1):233–265, 2014
2014
-
[38]
Well-posedness for the navier–stokes equations.�������� �� ������ ������, 157(1):22–35, 2001
Herbert Koch and Daniel Tataru. Well-posedness for the navier–stokes equations.�������� �� ������ ������, 157(1):22–35, 2001
2001
-
[39]
Forward self-similar solutions of the Navier-Stokes equations in the half space.����� ���, 9(8):1811–1827, 2016
Mikhail Korobkov and Tai-Peng Tsai. Forward self-similar solutions of the Navier-Stokes equations in the half space.����� ���, 9(8):1811–1827, 2016
2016
-
[40]
The forward self-similar solution of fractional incompressible navier-stokes system: The critical case.������� �� ���������� ��������, 287(7):110542, 2024
Baishun Lai. The forward self-similar solution of fractional incompressible navier-stokes system: The critical case.������� �� ���������� ��������, 287(7):110542, 2024
2024
-
[41]
Forward self-similar solutions of the fractional navier-stokes equations.�������� �� �����������, 352:981–1043, 2019
Baishun Lai, Changxing Miao, and Xiaoxin Zheng. Forward self-similar solutions of the fractional navier-stokes equations.�������� �� �����������, 352:981–1043, 2019
2019
-
[42]
Global regularity of weak solutions to the generalized Leray equations and its applications.������ ����� ����� ����, 374(10):7449–7497, 2021
Baishun Lai, Changxing Miao, and Xiaoxin Zheng. Global regularity of weak solutions to the generalized Leray equations and its applications.������ ����� ����� ����, 374(10):7449–7497, 2021
2021
-
[43]
Neˇ cas, M
J. Neˇ cas, M. R˚ uˇ ziˇ cka, and V.ˇSver´ ak. On leray’s self-similar solutions of the navier-stokes equations. ���� �����������, 176(2):283–294, Sep 1996. 52
1996
-
[44]
Infinitely many leray–hopf solutions for the fractional navier–stokes equations.���� ����������� �� ������� ����������� ���������, 44(4):335–365, 2019
Luigi De Rosa. Infinitely many leray–hopf solutions for the fractional navier–stokes equations.���� ����������� �� ������� ����������� ���������, 44(4):335–365, 2019
2019
-
[45]
Self-similar algebraic spiral solution of 2-d incompressible euler equations.������ �� ���, 11(1):13, May 2025
Feng Shao, Dongyi Wei, and Zhifei Zhang. Self-similar algebraic spiral solution of 2-d incompressible euler equations.������ �� ���, 11(1):13, May 2025
2025
-
[46]
STEIN and Timothy S
ELIAS M. STEIN and Timothy S. Murphy.�������� �������� ��������� ������������� �������� �������������� ��� ����������� ���������� ��������. Princeton University Press, 1993
1993
-
[47]
Forward discretely self-similar solutions of the navier–stokes equations.�������������� �� ������������ �������, 328(1):29–44, May 2014
Tai-Peng Tsai. Forward discretely self-similar solutions of the navier–stokes equations.�������������� �� ������������ �������, 328(1):29–44, May 2014
2014
-
[48]
On leray’s self-similar solutions of the navier-stokes equations satisfying local energy estimates.������� ��� �������� ��������� ��� ��������, 143(1):29–51, Aug 1998
Tai-Peng Tsai. On leray’s self-similar solutions of the navier-stokes equations satisfying local energy estimates.������� ��� �������� ��������� ��� ��������, 143(1):29–51, Aug 1998
1998
-
[49]
Instability and non-uniqueness in the cauchy problem for the euler equations of an ideal incompressible fluid
Misha Vishik. Instability and non-uniqueness in the cauchy problem for the euler equations of an ideal incompressible fluid. part i, 2018
2018
-
[50]
Instability and non-uniqueness in the cauchy problem for the euler equations of an ideal incompressible fluid
Misha Vishik. Instability and non-uniqueness in the cauchy problem for the euler equations of an ideal incompressible fluid. part ii, 2018
2018
-
[51]
Jiahong Wu. Lower bounds for an integral involving fractional laplacians and the generalized navier- stokes equations in besov spaces.�������������� �� ������������ �������, 263(3):803–831, May 2006. 53
2006
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