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Luigi De Rosa

Publications and source records attributed to Luigi De Rosa.

At least 19 recordsLinked to original sources
arXiv2026

Intermittency and Dissipation Regularity in Turbulence

We lay down a geometric-analytic framework to capture properties of energy dissipation within weak solutions to the incompressible Euler equations. For solutions with spatial Besov regularity, it is proved that the Duchon-Robert distribution has optimal improved regularity in a negative Besov space and, in the case it is a Radon measure, it is absolutely continuous with respect to a suitable Hausdorff measure. This imposes quantitative constraints on the dimension of the, possibly fractal, dissipative set and the admissible structure functions exponents, relating to the phenomenon of ''intermittency'' in turbulence. As a by-product of the approach, we also recover many known ''Onsager singularity'' type results.

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arXiv2026

Normal traces and applications to continuity equations on bounded domains

In this work, we study several properties of the normal Lebesgue trace of vector fields introduced by the second and third author in [22] in the context of the energy conservation for the Euler equations in Onsager-critical classes. Among other things, we prove that the normal Lebesgue trace satisfies the Gauss-Green identity and, by providing explicit counterexamples, that it is a notion sitting strictly between the distributional one for measure-divergence vector fields and the strong one for $BV$ functions. These results are then applied to the study of the uniqueness of weak solutions for continuity equations on bounded domains, allowing to remove the assumption in [19] of global $BV$ regularity up to the boundary, at least around the portion of the boundary where the characteristics exit the domain or are tangent. The proof relies on an explicit renormalization formula completely characterized by the boundary datum and the positive part of the normal Lebesgue trace. In the case when the characteristics enter the domain, a counterexample shows that achieving the normal trace in the Lebesgue sense is not enough to prevent non-uniqueness, and thus a $BV$ assumption seems to be necessary to get uniqueness.

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arXiv2026

Dissipation for codimension 1 singular structures in the incompressible Euler equations

We consider weak solutions to the incompressible Euler equations. It is shown that energy conservation holds in any Onsager critical class in which smooth functions are dense. The argument is independent of the specific critical regularity and the underlying PDE. This groups several energy conservation results and it suggests that critical spaces where smooth functions are dense are not at all different from subcritical ones, although possessing the "minimal" regularity index. Then, we study properties of the dissipation $D$ in the case of bounded solutions that are allowed to jump on $H^d$-rectifiable space-time sets $Σ$, which are the natural dissipative regions in the compressible setting. As soon as both the velocity and the pressure posses traces on $Σ$, it is shown that $Σ$ is $D$-negligible. The argument makes the role of the incompressibility very apparent, and it prevents dissipation on codimension 1 sets even if they happen to be densely distributed. As a corollary, we deduce energy conservation for bounded solutions of "special bounded deformation", providing the first energy conservation criterion in a critical class where only an assumption on the "longitudinal" increment is made, while the energy flux does not vanish for kinematic reasons.

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arXiv2026

Global Existence, Hamiltonian Conservation and Vanishing Viscosity for the Surface Quasi-Geostrophic Equation

For any initial datum $θ_0\in L^{\frac{4}{3}}_x$ it is proved the existence of a global-in-time weak solution $θ\in L^\infty_t L^{\frac43}_x$ to the surface quasi-geostrophic equation whose Hamiltonian, i.e. the $\dot{H}^{-\frac{1}{2}}_x$ norm, is constant in time. The solution is obtained as a vanishing viscosity limit. The main idea is to propagate in time the non-concentration of the $L^{\frac{4}{3}}_x$ norm of the initial data, from which the strong compactness in the Hamiltonian norm is deduced. Minimal Onsager supercritical conditions preventing anomalous dissipation are given.

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arXiv2026

Dissipation concentration in two-dimensional fluids

We study the dissipation measure arising in the inviscid limit of two-dimensional incompressible fluids. It is proved that the dissipation is Lebesgue in time and, for almost every time, it is absolutely continuous with respect to the defect measure of strong compactness of the solutions. When the initial vorticity is a measure, the dissipation is proved to be absolutely continuous with respect to a ''quadratic'' space-time vorticity measure. This results into the trivial measure if the initial vorticity has singular part of distinguished sign, or a spatially purely atomic measure if wild oscillations in time are ruled out. In fact, the dynamics at the Batchelor-Kraichnan dissipative scale is the only relevant one, in turn offering new criteria for anomalous dissipation. We provide kinematic examples highlighting the strengths and the limitations of our approach. Quantitative rates, dissipation life-span and steady fluids are also investigated.

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arXiv2026

Hamiltonian compactness and dissipation for the generalized SQG equation in the inviscid limit

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.

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arXiv2026

Quantitative enstrophy bounds for measure vorticities

We consider the two-dimensional incompressible Navier-Stokes equations with measure initial vorticity. By means of improved Nash inequalities, we establish quantitative estimates for the enstrophy depending on the absolute vorticity decay on balls. The bounds are optimal in several aspects and yield to a conjecturally sharp rate of the dissipation in the Delort's class.

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arXiv2025

No anomalous dissipation in two-dimensional incompressible fluids

We prove that any sequence of vanishing viscosity Leray-Hopf solutions to the periodic two-dimensional incompressible Navier-Stokes equations does not display anomalous dissipation if the initial vorticity is a measure with positive singular part. A key step in the proof is the use of the Delort-Majda concentration-compactness argument to exclude formation of atoms in the vorticity measure, which in particular implies that the limiting velocity is an admissible weak solution to Euler. This is the first result proving absence of dissipation in a class of solutions in which the velocity fails to be strongly compact in $L^2$, putting two-dimensional turbulence in sharp contrast with respect to that in three dimensions. Moreover, our proof reveals that the amount of energy dissipation can be bounded by the vorticity measure of a disk of size $\sqrt ν$, matching the two-dimensional Kolmogorov dissipative length scale which is expected to be sharp.

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arXiv2025

Sharp energy regularity and typicality results for Hölder solutions of incompressible Euler equations

This paper is devoted to show a couple of typicality results for weak solutions $v\in C^θ$ of the Euler equations, in the case $θ<1/3$. It is known that convex integration schemes produce wild weak solutions that exhibit anomalous dissipation of the kinetic energy $e_v$. We show that those solutions are typical in the Baire category sense. From [8], it is know that the kinetic energy $e_v$ of $θ$-Hölder continuous weak solution $v$ of the Euler equations satisfy $ e_v\in C^{\frac{2θ}{1-θ}}$. As a first result we prove that solutions with that behavior are a residual set in suitable complete metric space $X_θ$, that is contained in the space of all $C^θ$ weak solutions, whose choice is discussed at the end of the paper. More precisely we show that the set of solutions $v\in X_θ$ with $e_v \in C^{\frac{2θ}{1-θ}}$ but not to $\bigcup_{p\ge 1,\varepsilon>0}W^{\frac{2θ}{1-θ} + \varepsilon,p}(I)$ for any open $I \subset [0,T]$, are a residual set in $X_θ$. This, in particular, partially solves [9, Conjecture 1]. We also show that smooth solutions form a nowhere dense set in the space of all the $C^θ$ weak solutions. The technique is the same and what really distinguishes the two cases is that in the latter there is no need to introduce a different complete metric space with respect to the natural one.

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arXiv2024

On the Support of Anomalous Dissipation Measures

By means of a unifying measure-theoretic approach, we establish lower bounds on the Hausdorff dimension of the space-time set which can support anomalous dissipation for weak solutions of fluid equations, both in the presence or absence of a physical boundary. Boundary dissipation, which can occur at both the time and the spatial boundary, is analyzed by suitably modifying the Duchon & Robert interior distributional approach. One implication of our results is that any bounded Euler solution (compressible or incompressible) arising as a zero viscosity limit of Navier-Stokes solutions cannot have anomalous dissipation supported on a set of dimension smaller than that of the space. This result is sharp, as demonstrated by entropy-producing shock solutions of compressible Euler and by recent constructions of dissipative incompressible Euler solutions, as well as passive scalars. For $L^q_tL^r_x$ suitable Leray-Hopf solutions of the $d-$dimensional Navier-Stokes equation we prove a bound of the dissipation in terms of the Parabolic Hausdorff measure soon as the solution lies in the Prodi-Serrin class. In the three-dimensional case, this matches with the Caffarelli-Kohn-Nirenberg partial regularity.

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arXiv2024

Dissipation in Onsager's critical classes and energy conservation in $BV\cap L^\infty$ with and without boundary

This paper is concerned with the incompressible Euler equations. In Onsager's critical classes we provide explicit formulas for the Duchon-Robert measure in terms of the regularization kernel and a family of vector-valued measures $\{μ_z\}_z$, having some Hölder regularity with respect to the direction $z\in B_1$. Then, we prove energy conservation for $L^\infty_{x,t}\cap L^1_t BV_x$ solutions, in both the absence or presence of a physical boundary. This result generalises the previously known case of Vortex Sheets, showing that energy conservation follows from the structure of $L^\infty\cap BV$ incompressible vector fields rather than the flow having "organized singularities". The interior energy conservation features the use of Ambrosio's anisotropic optimization of the convolution kernel and it differs from the usual energy conservation arguments by heavily relying on the incompressibility of the vector field. This is the first energy conservation proof, for a given class of solutions, which fails to simultaneously apply to both compressible and incompressible models, coherently with compressible shocks having non-trivial entropy production. To run the boundary analysis we introduce a notion of "normal Lebesgue trace" for general vector fields, very reminiscent of the one for $BV$ functions. We show that having such a null normal trace is basically equivalent to have vanishing boundary energy flux. This goes beyond the previous approaches, laying down a setup which applies to every Lipschitz bounded domain. Allowing any Lipschitz boundary introduces several technicalities to the proof, with a quite geometrical/measure-theoretical flavour.

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arXiv2023

Intermittency and lower dimensional dissipation in incompressible fluids

In the context of incompressible fluids, the observation that turbulent singular structures fail to be space filling is known as ``intermittency'' and it has strong experimental foundations. Consequently, as first pointed out by Landau, real turbulent flows do not satisfy the central assumptions of homogeneity and self-similarity in the K41 theory, and the K41 prediction of structure function exponents $ζ_p=\frac{p}{3}$ might be inaccurate. In this work we prove that, in the inviscid case, energy dissipation that is lower-dimensional in an appropriate sense implies deviations from the K41 prediction in every $p-$th order structure function for $p>3$. By exploiting a Lagrangian-type Minkowski dimension that is very reminiscent of the Taylor's frozen turbulence hypothesis, our strongest upper bound on $ζ_p$ coincides with the $β-$model proposed by Frisch, Sulem and Nelkin in the late 70s, adding some rigorous analytical foundations to the model. More generally we explore the relationship between dimensionality assumptions on the dissipation support and restrictions on the $p-$th order absolute structure functions. This approach differs from the current mathematical works on intermittency by its focus on geometrical rather than purely analytical assumptions. The proof is based on a new local variant of the celebrated Constantin-E-Titi argument that features the use of a third order commutator estimate, the special double regularity of the pressure, and mollification along the flow of a vector field.

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arXiv2023

Full double Hölder regularity of the pressure in bounded domains

We consider Hölder continuous weak solutions $u\in C^γ(Ω)$, $u\cdot n|_{\partial Ω}=0$, of the incompressible Euler equations on a bounded and simply connected domain $Ω\subset\mathbb{R}^d$. If $Ω$ is of class $C^{2,1}$ then the corresponding pressure satisfies $p\in C^{2γ}_*(Ω)$ in the case $γ\in (0,\frac{1}{2}]$, where $C^{2γ}_*$ is the Hölder-Zygmund space, which coincides with the usual Hölder space for $γ<\frac12$. This result, together with our previous one in [11] covering the case $γ\in(\frac12,1)$, yields the full double regularity of the pressure on bounded and sufficiently regular domains. The interior regularity comes from the corresponding $C^{2γ}_*$ estimate for the pressure on the whole space $\mathbb{R}^d$, which in particular extends and improves the known double regularity results (in the absence of a boundary) in the borderline case $γ=\frac{1}{2}$. The boundary regularity features the use of local normal geodesic coordinates, pseudodifferential calculus and a fine Littlewood-Paley analysis of the modified equation in the new coordinate system. We also discuss the relation between different notions of weak solutions, a step which plays a major role in our approach.

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arXiv2023

Fine properties of symmetric and positive matrix fields with bounded divergence

This paper is concerned with various fine properties of the functional \[ \mathbb{D}(A) = \int_{\mathbb{T}^n}{\text{det}}^\frac{1}{n-1}(A(x))\,dx \] introduced in [33]. This functional is defined on $X_p$, which is the cone of matrix fields $A \in L^p(\mathbb{T}^n;\text{Sym}^+(n))$ with $\text{div }(A)$ a bounded measure. We start by correcting a mistake we noted in our [13, Corollary 7], which concerns the upper semicontinuity of $\mathbb{D}(A)$ in $X_p$. We give a proof of a refined correct statement, and we will use it to study the behaviour of $\mathbb{D}(A)$ when $A \in X_\frac{n}{n-1}$, which is the critical integrability for $\mathbb{D}(A)$. One of our main results gives an explicit bound of the measure generated by $\mathbb{D}(A_k)$ for a sequence of such matrix fields $\{A_k\}_k$. In particular it allows us to characterize the upper semicontinuity of $\mathbb{D}(A)$ in the case $A \in X_\frac{n}{n - 1}$ in terms of the measure generated by the variation of $\{\text{div } A_k\}_k$. We show by explicit example that this characterization fails in $X_p$ if $p<\frac{n}{n-1}$. As a by-product of our characterization we also recover and generalize a result of P.-L. Lions [25,26] on the lack of compactness in the study of Sobolev embeddings. Furthermore, in analogy with Monge-Ampère theory, we give sufficient conditions under which $\text{det}^\frac{1}{n-1}(A)$ is Hardy when $A \in X_\frac{n}{n - 1}$, generalising the celebrated result of S. Müller [29] when $A=\text{cof } D^2φ$, for a convex function $φ$.

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arXiv2023

Weak-strong uniqueness and vanishing viscosity for incompressible Euler equations in exponential spaces

In the class of admissible weak solutions, we prove a weak-strong uniqueness result for the incompressible Euler equations assuming that the symmetric part of the gradient belongs to $L^1_{\rm loc}([0,+\infty);L^{\rm exp}(\mathbb{R}^d;\mathbb{R}^{d\times d}))$, where $L^{\rm exp}$ denotes the Orlicz space of exponentially integrable functions. Moreover, under the same assumptions on the limit solution to the Euler system, we obtain the convergence of vanishing-viscosity Leray--Hopf weak solutions of the Navier--Stokes equations.

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arXiv2023

On Double Hölder Regularity of the Hydrodynamic Pressure in Bounded Domains

We prove that the hydrodynamic pressure $p$ associated to the velocity $u\in C^θ(Ω)$, $θ\in(0,1)$, of an inviscid incompressible fluid in a bounded and simply connected domain $Ω\subset \mathbb R^d$ with $C^{2+}$ boundary satisfies $p\in C^θ(Ω)$ for $θ\leq \frac12$ and $p\in C^{1,2θ-1}(Ω)$ for $θ>\frac12$. Moreover, when $\partial Ω\in C^{3+}$, we prove that an almost double Hölder regularity $p\in C^{2θ-}(Ω)$ holds even for $θ<\frac12$. This extends and improves the recent result of Bardos and Titi obtained in the planar case to every dimension $d\ge2$ and it also doubles the pressure regularity. Differently from Bardos and Titi, we do not introduce a new boundary condition for the pressure, but instead work with the natural one. In the boundary-free case of the $d$-dimensional torus, we show that the double regularity of the pressure can be actually achieved under the weaker assumption that the divergence of the velocity is sufficiently regular, thus not necessarily zero.

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arXiv2022

On a question of D. Serre

In this paper we give a negative answer to the question posed in [15, Open Question 2.1] about possible gains of integrability of determinants of divergence-free, non-negative definite matrix-fields. We also analyze the case in which the matrix-field is given by the Hessian of a convex function.

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arXiv2021

A fractal version of the Onsager's conjecture: the $β-$model

Intermittency phenomena are known to be among the main reasons why Kolmogorov's theory of fully developed Turbulence is not in accordance with several experimental results. This is why some \emph{fractal} statistical models have been proposed in order to realign the theoretical physical predictions with the empirical experiments. They indicate that energy dissipation, and thus singularities, are not space filling for high Reynolds numbers. This note aims to give a precise mathematical statement on the energy conservation of such fractal models of Turbulence. We prove that for $θ-$Hölder continuous weak solutions of the incompressible Euler equations energy conservation holds if the upper Minkowski dimension of the spatial singular set $S \subseteq \T^3$ (possibly also time-dependent) is small, or more precisely if $\overline{\dim}_{\mathcal{M}}(S)<2+3θ\,.$ In particular, the spatial singularities of \emph{non-conservative} $θ-$Hölder continuous weak solutions of Euler are concentrated on a set with dimension lower bound $2+3θ$. This result can be viewed as the fractal counterpart of the celebrated Onsager conjecture and it matches both with the prediction given by the $β-$model introduced by Frisch, Sulem and Nelkin in \cite{FSN78} and with other mathematical results in the endpoint cases.

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