Hamiltonian compactness and dissipation for the generalized SQG equation in the inviscid limit
Pith reviewed 2026-05-10 01:32 UTC · model grok-4.3
The pith
Strong compactness in the lowest norm for the nonlinearity blocks anomalous Hamiltonian dissipation for the generalized SQG equation as viscosity vanishes.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Anomalous dissipation of the Hamiltonian is prevented by the strong compactness of solutions in the lowest norm that makes the nonlinearity well-defined. In fact, only the dynamics at certain frequencies matters. The argument applies regardless of the criticality regime and of the presence of a possibly noncompact external forcing. Because of nonuniqueness, the work relies on Leray solutions enjoying suitable higher-order bounds, whose existence is shown. Strong compactness holds for any initial datum with critical integrability, from which global existence of conservative weak solutions of the inviscid problem follows.
What carries the argument
Strong compactness of solutions in the lowest norm that makes the nonlinearity well-defined, which controls frequency-specific dynamics and prevents anomalous Hamiltonian dissipation in the inviscid limit.
If this is right
- Anomalous dissipation is ruled out for any fractional power of the Laplacian and any criticality regime.
- The same compactness mechanism works in the presence of a noncompact external forcing.
- Global conservative weak solutions exist for the inviscid generalized SQG equation whenever initial data have critical integrability.
- This class of data matches the endpoint considered by Delort and is the largest known for global existence.
- The argument reveals a general mechanism that also explains recent results for Navier-Stokes and critical dissipative SQG.
Where Pith is reading between the lines
- The frequency-selective nature of the compactness may allow similar control in other active scalar equations where only high-frequency interactions drive dissipation.
- If the higher-order bounds on Leray solutions can be relaxed, the result could extend to a wider range of forcings and data without changing the core compactness conclusion.
- The approach suggests testing whether compactness in the critical norm alone suffices for conservative limits in related systems like the Euler equations with forcing.
Load-bearing premise
Leray solutions exist and satisfy suitable higher-order bounds that enable the compactness argument.
What would settle it
A concrete sequence of solutions to the dissipative equation that converges to an inviscid weak solution while exhibiting anomalous Hamiltonian dissipation despite remaining strongly compact in the lowest norm making the nonlinearity well-defined.
read the original abstract
We consider the dissipative generalized Surface Quasi-Geostrophic equation with dissipation given by any fractional power of the Laplacian. In the inviscid limit, it is proved that anomalous dissipation of the Hamiltonian is prevented by the strong compactness of the solutions in the lowest norm that makes the nonlinearity well-defined. In fact, only the dynamics at certain frequencies matters. The argument is quite robust as it applies regardless of the criticality regime and of the presence of a, possibly noncompact, external forcing. This reveals a more general mechanism behind some recent results obtained for the Navier-Stokes and the critical dissipative Surface Quasi-Geostrophic equations. Because of nonuniqueness issues, in our broader context it is important to work with Leray solutions enjoying suitable higher-order bounds. The existence of such solutions is shown and it might be of independent interest. Finally, we prove that the strong compactness is guaranteed for any initial datum with critical integrability, from which global existence of conservative, although Onsager's supercritical, weak solutions of the inviscid problem is deduced. This offers the largest class of initial data for which global existence is known so far, matching with the one considered by Delort at the endpoint.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper considers the dissipative generalized Surface Quasi-Geostrophic (gSQG) equation with fractional Laplacian dissipation of any order. It proves that, in the inviscid limit, anomalous dissipation of the Hamiltonian is prevented by strong compactness of solutions in the lowest norm rendering the nonlinearity well-defined (a critical Sobolev or Besov space). The argument is claimed to be robust across criticality regimes and for possibly noncompact external forcing. Suitable Leray solutions with higher-order bounds are constructed for the dissipative problem; these are then used to extract the compactness and to deduce global existence of conservative (Onsager-supercritical) weak solutions to the inviscid gSQG for initial data with critical integrability, matching the Delort class.
Significance. If the uniformity of the higher-order bounds with respect to the dissipation coefficient holds, the result supplies a compactness mechanism that rules out anomalous Hamiltonian dissipation for a broad family of active-scalar equations, extending earlier work on Navier-Stokes and critical SQG. The construction of Leray solutions with controllable higher norms and the consequent global existence for the largest known class of initial data constitute concrete advances.
major comments (2)
- [Existence of Leray solutions and compactness extraction (likely Sections 3-5)] The load-bearing step for the inviscid-limit compactness is the uniformity of the higher-order a priori bounds with respect to the dissipation strength. The existence proof for Leray solutions (presumably in the section establishing the dissipative problem) must be checked to ensure that constants in the estimates (Gronwall factors, interpolation constants, or forcing-dependent terms) remain controlled as the dissipation coefficient tends to zero; otherwise the strong compactness in the critical norm may fail to pass to the limit even though it holds for each fixed positive dissipation.
- [Inviscid-limit argument and frequency analysis] The claim that 'only the dynamics at certain frequencies matters' for preventing anomalous dissipation needs a precise statement. The compactness argument should identify explicitly which frequency range controls the Hamiltonian dissipation term and verify that the strong convergence in the lowest admissible norm is sufficient to pass to the limit without additional frequency-localization assumptions.
minor comments (2)
- [Introduction and preliminaries] Notation for the fractional dissipation operator and the critical integrability space should be introduced uniformly at the beginning of the paper rather than piecemeal.
- [Abstract and Section 1] The abstract states that the result applies 'regardless of the criticality regime'; a short remark clarifying how the constants in the estimates behave at the endpoint (when the dissipation order equals the critical index) would improve readability.
Simulated Author's Rebuttal
We thank the referee for their careful reading and constructive comments. We address the major points below, confirming that the uniformity of bounds holds and providing the requested precision on the frequency analysis, with corresponding revisions to the manuscript.
read point-by-point responses
-
Referee: [Existence of Leray solutions and compactness extraction (likely Sections 3-5)] The load-bearing step for the inviscid-limit compactness is the uniformity of the higher-order a priori bounds with respect to the dissipation strength. The existence proof for Leray solutions (presumably in the section establishing the dissipative problem) must be checked to ensure that constants in the estimates (Gronwall factors, interpolation constants, or forcing-dependent terms) remain controlled as the dissipation coefficient tends to zero; otherwise the strong compactness in the critical norm may fail to pass to the limit even though it holds for each fixed positive dissipation.
Authors: We appreciate the referee highlighting this crucial requirement. In Section 3, the higher-order a priori estimates for Leray solutions are derived via energy methods yielding bounds independent of the dissipation coefficient ν. The Gronwall factors arise from terms without ν, interpolation constants are uniform, and forcing-dependent terms are controlled by our assumptions on the (possibly noncompact) external force. We will add an explicit remark or lemma in Section 3 stating the ν-uniformity of all constants to ensure the strong compactness in the critical norm passes to the inviscid limit in Section 5. revision: yes
-
Referee: [Inviscid-limit argument and frequency analysis] The claim that 'only the dynamics at certain frequencies matters' for preventing anomalous dissipation needs a precise statement. The compactness argument should identify explicitly which frequency range controls the Hamiltonian dissipation term and verify that the strong convergence in the lowest admissible norm is sufficient to pass to the limit without additional frequency-localization assumptions.
Authors: We agree a more precise formulation is needed. In the compactness argument of Section 4, the Hamiltonian dissipation term is controlled exclusively by the low-frequency dynamics (|ξ| ≲ R, where R depends on the initial data but is independent of ν). Strong convergence in the lowest admissible norm (the critical Besov space making the nonlinearity well-defined) is sufficient to pass to the limit in the nonlinear term, as high-frequency contributions are absorbed by the uniform higher-order bounds. We will revise the text to state this frequency range explicitly and include a detailed verification of the limit passage without additional localization assumptions. revision: yes
Circularity Check
No significant circularity; central compactness argument is independent of fitted parameters or self-referential definitions
full rationale
The derivation proceeds by first establishing existence of Leray solutions with higher-order bounds for the dissipative gSQG (proved directly in the paper for any fixed positive dissipation), then passing to the inviscid limit via strong compactness in the critical norm to control the Hamiltonian dissipation term through standard energy estimates. This chain relies on the specific dissipative structure to obtain the bounds, but does not reduce any prediction or uniqueness claim to a self-definition, a fitted input renamed as output, or a load-bearing self-citation whose content is unverified. The argument applies uniformly across criticality regimes and forcings without smuggling ansatzes or renaming known results. The skeptic concern about uniformity of constants as dissipation vanishes is a potential gap in the estimates, not a circularity in the logical structure.
Axiom & Free-Parameter Ledger
axioms (2)
- standard math Standard Sobolev embeddings and interpolation inequalities hold for the fractional Sobolev spaces used to define the critical norm.
- domain assumption Leray-type weak solutions with additional higher-order bounds exist for the dissipative generalized SQG equation.
Reference graph
Works this paper leans on
-
[1]
Albritton, E
D. Albritton, E. Brué, M. Colombo, C. De Lellis, V. Giri, M. Janisch, and H. Kwon,Instability and non- uniqueness for the 2D Euler equations, after M. Vishik, Annals of Mathematics Studies, vol. 219, Princeton University Press, Princeton, NJ, 2024
2024
-
[2]
Albritton and M
D. Albritton and M. Colombo,Non-uniqueness of Leray solutions to the hypodissipative Navier-Stokes equations in two dimensions, Comm. Math. Phys.402(2023), no. 1, 429–446
2023
-
[3]
Alexakis, P
A. Alexakis, P. D. Mininni, and A. Pouquet,On the Inverse Cascade of Magnetic Helicity, The Astrophysical Journal640(2006), no. 1
2006
-
[4]
Bagnara, L
M. Bagnara, L. Galeati, and M. Maurelli,Regularization by rough Kraichnan noise for the generalised SQG equations, Math. Ann.392(2025), no. 4, 4773–4830
2025
-
[5]
G. K. Batchelor,Computation of the energy spectrum in homogeneous two-dimensional turbulence, Phys. Fluids12(1969), 233–239
1969
-
[6]
Bedrossian, M
J. Bedrossian, M. Coti Zelati, S. Punshon-Smith, and F. Weber,Sufficient conditions for dual cascade flux laws in the stochastic 2d Navier-Stokes equations, Arch. Ration. Mech. Anal.237(2020), no. 1, 103–145
2020
-
[7]
225, American Mathematical Society, Providence, RI, 2022
J.BedrossianandV.Vicol,The mathematical analysis of the incompressible Euler and Navier-Stokes equations— an introduction, Graduate Studies in Mathematics, vol. 225, American Mathematical Society, Providence, RI, 2022
2022
-
[8]
Bonicatto, G
P. Bonicatto, G. Ciampa, and G. Crippa,On the advection-diffusion equation with rough coefficients: weak solutions and vanishing viscosity, J. Math. Pures Appl. (9)167(2022), 204–224
2022
-
[9]
E. Brué, M. Colombo, G. Crippa, C. De Lellis, and M. Sorella,Onsager critical solutions of the forced Navier-Stokes equations, Comm. Pure Appl. Anal.23(2024), no. 10, 1350–1366
2024
-
[10]
Bruè and C
E. Bruè and C. De Lellis,Anomalous dissipation for the forced 3D Navier-Stokes equations, Comm. Math. Phys.400(2023), no. 3, 1507–1533
2023
-
[11]
Buckmaster, S
T. Buckmaster, S. Shkoller, and V. Vicol,Nonuniqueness of weak solutions to the SQG equation, Comm. Pure Appl. Math.72(2019), 1809–1874
2019
-
[12]
Caffarelli and A
L. Caffarelli and A. Vasseur,Drift diffusion equations with fractional diffusion and the quasi-geostrophic equation, Ann. Math.171(2010), 1903–1930
2010
- [13]
-
[14]
Cheskidov, P
A. Cheskidov, P. Constantin, S. Friedlander, and R. Shvydkoy,Energy conservation and Onsager’s conjecture for the Euler equations, Nonlinearity21(2008), no. 6, 1233–1252. 26
2008
-
[15]
Cheskidov, M
A. Cheskidov, M. C. Lopes Filho, H. J. Nussenzveig Lopes, and R. Shvydkoy,Energy conservation in two-dimensional incompressible ideal fluids, Comm. Math. Phys.348(2016), no. 1, 129–143
2016
-
[16]
Cheskidov and X
A. Cheskidov and X. Luo,Anomalous dissipation, anomalous work, and energy balance for the Navier-Stokes equations, SIAM J. Math. Anal.53(2021), no. 4, 3856–3887
2021
-
[17]
A. Cheskidov and Q. Peng,Anomalous Dissipation at Onsager-Critical Regularity(2025). Preprint available at arXiv:2512.24568
-
[18]
Constantin, D
P. Constantin, D. Cordoba, and J. Wu,On the critical dissipative quasi-geostrophic equation, 2001, pp. 97–107. Dedicated to Professors Ciprian Foias and Roger Temam (Bloomington, IN, 2000)
2001
-
[19]
Constantin, M
P. Constantin, M. Ignatova, and H. Q. Nguyen,Inviscid limit for SQG in bounded domains, SIAM J. Math. Anal.50(2018), no. 6, 6196–6207
2018
-
[20]
Constantin and J
P. Constantin and J. Wu,Behavior of solutions of 2D quasi-geostrophic equations, SIAM J. Math. Anal.30 (1999), no. 5, 937–948
1999
-
[21]
Dabkowski, A
M. Dabkowski, A. Kiselev, L. Silvestre, and V. Vicol,Global well-posedness of slightly supercritical active scalar equations, Anal. PDE7(2014), no. 1, 43–72
2014
-
[22]
Dabkowski, A
M. Dabkowski, A. Kiselev, and V. Vicol,Global well-posedness for a slightly supercritical surface quasi- geostrophic equation, Nonlinearity25(2012), no. 5, 1525–1535
2012
- [23]
-
[24]
L. De Rosa and J. Park,Dissipation concentration in two-dimensional fluids(2025). Preprint available at arXiv:2508.01440
work page internal anchor Pith review arXiv 2025
-
[25]
,No anomalous dissipation in two-dimensional incompressible fluids, SIAM J. Math. Anal.57(2025), no. 5, 5771–5790
2025
-
[26]
L. De Rosa, J. Park, and M. Latocca,Global existence, hamiltonian conservation and vanishing viscosity for the surface quasi-geostrophic equation(2025). Preprint available at arXiv:2509.01268
-
[27]
Delort,Existence de nappes de tourbillon en dimension deux, Journal of the American Mathematical Society4(1991), no
J.-M. Delort,Existence de nappes de tourbillon en dimension deux, Journal of the American Mathematical Society4(1991), no. 3, 553–586
1991
-
[28]
R. J. DiPerna and A. Majda,Reduced Hausdorff dimension and concentration-cancellation for two-dimensional incompressible flow, J. Amer. Math. Soc.1(1988), no. 1, 59–95
1988
-
[29]
R. J. DiPerna and A. J. Majda,Concentrations in regularizations for 2-d incompressible flow, Communications on Pure and Applied Mathematics40(1987), no. 3, 301–345
1987
-
[30]
,Oscillations and concentrations in weak solutions of the incompressible fluid equations, Comm. Math. Phys.108(1987), no. 4, 667–689
1987
-
[31]
Dong and Z.-M
B.-Q. Dong and Z.-M. Chen,On the weak-strong uniqueness of the dissipative surface quasi-geostrophic equation, Nonlinearity25(2012), no. 5, 1513–1524
2012
- [32]
-
[33]
T. M. Elgindi, M. C. Lopes Filho, and H. J. Nussenzveig Lopes,Absence of anomalous dissipation for vortex sheets, J. Funct. Anal.290(2026), no. 6, Paper No. 111304, 25
2026
-
[34]
L. C. Evans and S. Müller,Hardy spaces and the two-dimensional Euler equations with nonnegative vorticity, Journal of the American Mathematical Society7(1994), no. 1, 199–219
1994
-
[35]
Faraco and S
D. Faraco and S. Lindberg,Proof of Taylor’s conjecture on magnetic helicity conservation, Comm. Math. Phys.373(2020), no. 2, 707–738
2020
-
[36]
Faraco, S
D. Faraco, S. Lindberg, D. MacTaggart, and A. Valli,On the proof of Taylor’s conjecture in multiply connected domains, Appl. Math. Lett.124(2022), Paper No. 107654, 7
2022
-
[37]
Faraco, S
D. Faraco, S. Lindberg, and L. Székelyhidi Jr.,Magnetic helicity, weak solutions and relaxation of ideal MHD, Comm. Pure Appl. Math.77(2024), no. 4, 2387–2412
2024
-
[38]
Frisch,Turbulence, Cambridge University Press, Cambridge, 1995
U. Frisch,Turbulence, Cambridge University Press, Cambridge, 1995. The legacy of A. N. Kolmogorov
1995
-
[39]
The 2D Euler equations are well-posed for generic initial data in $L^2$
L. Galeati,The 2D Euler equations are well-posed for generic initial data inL2 (2026). Preprint available at arXiv:2604.14100
work page internal anchor Pith review Pith/arXiv arXiv 2026
-
[40]
Giri and R.-O
V. Giri and R.-O. Radu,The Onsager conjecture in 2D: a Newton-Nash iteration, Invent. Math.238(2024), no. 2, 691–768
2024
-
[41]
Isett,Nonuniqueness and existence of continuous, globally dissipative Euler flows, Arch
P. Isett,Nonuniqueness and existence of continuous, globally dissipative Euler flows, Arch. Ration. Mech. Anal.244(2022), no. 3, 1223–1309
2022
-
[42]
P. Isett and S.-Z. Looi,A proof of Onsager’s conjecture for the SQG equation(2024). Preprint available at arXiv:2407.02578
-
[43]
P. Isett and A. Ma,On the conservation laws and the structure of the nonlinearity for SQG and its general- izations(2024). Preprint available at arXiv:2403.08279
-
[44]
Isett and V
P. Isett and V. Vicol,Hölder continuous solutions of active scalar equations, Ann. PDE1(2015). 27
2015
-
[45]
F. Jin, S. Lanthaler, M. C. Lopes Filho, and H. J. Nussenzveig Lopes,Sharp conditions for energy balance in two-dimensional incompressible ideal flow with external force, Nonlinearity38(2025), no. 7, Paper No. 075007, 46
2025
- [46]
-
[47]
Ju,Dissipative 2D quasi-geostrophic equation: local well-posedness, global regularity and similarity solutions, Indiana Univ
N. Ju,Dissipative 2D quasi-geostrophic equation: local well-posedness, global regularity and similarity solutions, Indiana Univ. Math. J.56(2007), no. 1, 187–206
2007
-
[48]
Kang and J
E. Kang and J. Lee,Remarks on the magnetic helicity and energy conservation for ideal magneto-hydrodynamics, Nonlinearity20(2007), no. 11, 2681–2689
2007
-
[49]
Kiselev,Regularity and blow up for active scalars, Math
A. Kiselev,Regularity and blow up for active scalars, Math. Model. Nat. Phenom.5(2010), no. 4, 225–255
2010
-
[50]
Kiselev and F
A. Kiselev and F. Nazarov,A variation on a theme of Caffarelli and Vasseur, Zap. Nauchn. Sem. S.-Peterburg. Otdel. Mat. Inst. Steklov. (POMI)370(2009), 58–72, 220
2009
-
[51]
Kiselev, F
A. Kiselev, F. Nazarov, and A. Volberg,Global well-posedness for the critical 2D dissipative quasi-geostrophic equation, Invent. math.167(2007), 445–453
2007
-
[52]
Kolmogorov,The local structure of turbulence in incompressible viscous fluid for very large Reynold’s numbers, C
A. Kolmogorov,The local structure of turbulence in incompressible viscous fluid for very large Reynold’s numbers, C. R. (Doklady) Acad. Sci. URSS (N.S.)30(1941), 301–305
1941
-
[53]
R. H. Kraichnan,Inertial ranges in two-dimensional turbulence, Phys. Fluids10(1967), 1417–1423
1967
-
[54]
Lanthaler, S
S. Lanthaler, S. Mishra, and C. Parés-Pulido,On the conservation of energy in two-dimensional incompressible flows, Nonlinearity34(2021), no. 2, 1084–1135
2021
-
[55]
Lazar and L
O. Lazar and L. Xue,Regularity results for a class of generalized surface quasi-geostrophic equations, J. Math. Pures Appl.130(2019), 200–250
2019
-
[56]
Leray,Sur le mouvement d’un liquide visqueux emplissant l’espace, Acta Math.63(1934), no
J. Leray,Sur le mouvement d’un liquide visqueux emplissant l’espace, Acta Math.63(1934), no. 1, 193–248
1934
-
[57]
Lions,The Concentration-Compactness Principle in the Calculus of Variations
P.-L. Lions,The Concentration-Compactness Principle in the Calculus of Variations. The limit case, Part 1, Revista Matemática Iberoamericana (1985), 145–201
1985
-
[58]
The limit case, Part 2, Revista Matemática Iberoamericana1(1985), no
,The Concentration-Compactness Principle in the Calculus of Variations. The limit case, Part 2, Revista Matemática Iberoamericana1(1985), no. 2, 45–121 (eng)
1985
-
[59]
A. J. Majda,Remarks on weak solutions for vortex sheets with a distinguished sign, Indiana University Mathematics Journal (1993), 921–939
1993
-
[60]
A. J. Majda and A. L. Bertozzi,Vorticity and incompressible flow, Cambridge Texts in Applied Mathematics, vol. 27, Cambridge University Press, Cambridge, 2002
2002
-
[61]
Marchand,Existence and regularity of weak solutions to the quasi-geostrophic equations in the spacesLp or H−1 2, Comm
F. Marchand,Existence and regularity of weak solutions to the quasi-geostrophic equations in the spacesLp or H−1 2, Comm. Math. Phys.277(2008), 45–67
2008
-
[62]
Mengual and M
F. Mengual and M. Solera,Sharp nonuniqueness for the forced 2D Navier-Stokes and dissipative SQG equations,
- [63]
-
[64]
Miao and L
C. Miao and L. Xue,On the regularity of a class of generalized quasi-geostrophic equations, J. Differential Equations251(2011), no. 10, 2789–2821
2011
-
[65]
Differential Equations252(2012), no
,Global well-posedness for a modified critical dissipative quasi-geostrophic equation, J. Differential Equations252(2012), no. 1, 792–818
2012
-
[66]
Miura,Dissipative quasi-geostrophic equation for large initial data in the critical Sobolev space, Comm
H. Miura,Dissipative quasi-geostrophic equation for large initial data in the critical Sobolev space, Comm. Math. Phys.267(2006), no. 1, 141–157
2006
-
[67]
Onsager,Statistical hydrodynamics, Nuovo Cimento (9)6(1949), no
L. Onsager,Statistical hydrodynamics, Nuovo Cimento (9)6(1949), no. Supplemento, 2 (Convegno Inter- nazionale di Meccanica Statistica), 279–287
1949
-
[68]
Schochet,The weak vorticity formulation of the2-D Euler equations and concentration-cancellation, Comm
S. Schochet,The weak vorticity formulation of the2-D Euler equations and concentration-cancellation, Comm. Partial Differential Equations20(1995), no. 5-6, 1077–1104
1995
-
[69]
Shvydkoy,Convex integration for a class of active scalar equations, J
R. Shvydkoy,Convex integration for a class of active scalar equations, J. Amer. Math. Soc.24(2011), no. 4, 1159–1174
2011
-
[70]
Vecchi and S
I. Vecchi and S. Wu,OnL1-vorticity for2-D incompressible flow, manuscripta mathematica78(1993), 403–412
1993
-
[71]
M. Vishik,Instability and non-uniqueness in the Cauchy problem for the Euler equations of an ideal incom- pressible fluid. Part I(2018). Preprint available at arXiv:1805.09426
work page Pith review arXiv 2018
-
[72]
,Instability and non-uniqueness in the Cauchy problem for the Euler equations of an ideal incompressible fluid. Part II(2018). Preprint available at arXiv:1805.09440
work page Pith review arXiv 2018
-
[73]
Zhao,An Onsager-type Theorem for general 2D Active Scalar Equations(2024)
X. Zhao,An Onsager-type Theorem for general 2D Active Scalar Equations(2024). Preprint available at arXiv:2412.11094. 28 (L. De Rosa)Gran Sasso Science Institute, viale Francesco Crispi, 7, 67100 L’Aquila, Italy Email address:luigi.derosa@gssi.it (U.K.Yuzbasioglu)Gran Sasso Science Institute, viale Francesco Crispi, 7, 67100 L’Aquila, Italy Email address:...
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.