Cristiana De Filippis
We provide quantitative gradient bounds for solutions to certain parabolic equations with unbalanced polynomial growth and non-smooth coefficients.
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Higher Hölder regularity for nonlocal parabolic equations with irregular kernels
本文研究了具有不规则核系数的非局部抛物型方程，在对非齐次项施加适当高阶可积性且对核系数作最小正则性假设的条件下，建立了该方程的高阶Hölder正则性。
We prove the natural weighted Calderón and Zygmund estimates for solutions to elliptic and parabolic obstacle problems in nondivergence form with discontinuous coefficients and irregular obstacles. We also obtain Morrey regularity results for the Hessian of the solutions and Hölder continuity of the gradient of the solutions.
We prove Schauder estimates for solutions to both divergence and non-divergence type higher-order parabolic systems in the whole space and the half space. We also provide an existence result for divergence type systems in a cylindrical domain. All coefficients are assumed to be only measurable in the time variable and Hölder continuous in the spatial variables.
We prove the $W^{1,2}_p$-estimate and solvability for the Dirichlet problem of second-order parabolic equations in simple convex polytopes with time irregular coefficients, when $p\in (1,2]$. We also consider the corresponding Neumann problem in a half space when $p\in [2,\infty)$. Similar results are obtained for equations in a half space with coefficients which are measurable in a tangential direction and have small mean oscillations in the other directions.
The solvability in Sobolev spaces is proved for divergence form complex-valued higher order parabolic systems in the whole space, on a half space, and on a Reifenberg flat domain. The leading coefficients are assumed to be merely measurable in one spacial direction and have small mean oscillations in the orthogonal directions on each small cylinder. The directions in which the coefficients are only measurable vary depending on each cylinder. The corresponding elliptic problem is also considered.
A priori estimates for general elliptic and parabolic boundary value problems over irregular domains
本文提出了一种统一方法，用于处理一般椭圆和抛物边值问题在不规则区域上的先验估计，涵盖多种边界条件和应用领域。
We consider the parabolic-elliptic Keller-Segel system \[ \left\{ \begin{aligned} u_t &= Δu - χ\nabla \cdot (u \nabla v), \\ 0 &= Δv - v + u \end{aligned} \right. \tag{$\star$} \] in a smooth bounded domain $Ω\subseteq \mathbb{R}^n$, $n\in\mathbb{N}$, with Neumann boundary conditions. We look at both chemotactic attraction ($χ> 0$) and repulsion ($χ< 0$) scenarios in two and three dimensions. The key feature of interest for the purposes of this paper is under which conditions said system still admits global classical solutions due to the smoothing properties of the Laplacian even if the initia…
We construct examples of blowup from smooth data for complex-valued solutions to linear uniformly parabolic equations in dimension $n \geq 2$, which are exactly as irregular as parabolic energy estimates allow.
We prove Hölder regularity for a general class of parabolic integro-differential equations, which (strictly) includes many previous results. We present a proof which avoids the use of a convex envelop as well as give a new covering argument which is better suited to the fractional order setting. Our main result involves a class of kernels which may contain a singular measure, may vanish at some points, and are not required to be symmetric. This new generality of integro-differential operators opens the door to further applications of the theory, including some regularization estimates for the …
We obtain Calderón-Zygmund type estimates for parabolic equations with Orlicz growth, where nonlinearities involved in the equations may be discontinuous for the space and time variables. In addition, we consider parabolic systems with the Uhlenbeck structure.
We introduce elliptic and parabolic $\mathcal{B}_{1}$ classes that generalize the well-known $\mathfrak{B}_{p}$ classes of DeGiorgi, Ladyzhenskaya and Ural'tseva with $p>1$. New classes are applied to prove pointwise continuity of solutions of elliptic and parabolic equations with nonstandard growth conditions. Our considerations cover new cases of variable exponent and $(p, q)$-phase growth including the ,,singular-degenerate'' parabolic case $p<2<q$.
We establish the pointwise continuity of bounded weak solutions to of a class of scalar parabolic equations and strongly coupled parabolic systems. Our approach to the regularity theory of parabolic scalar equations is quite elementary and its applications to strongly coupled systems does not require higher $L^p$ integrability of derivatives.
We establish global regularity for weak solutions to quasilinear divergence form elliptic and parabolic equations over Lipschitz domains with controlled growth conditions on low order terms. The leading coefficients belong to the class of BMO functions with small mean oscillations with respect to $x$.
We prove generalized Fefferman-Stein type theorems on sharp functions with $A_p$ weights in spaces of homogeneous type with either finite or infinite underlying measure. We then apply these results to establish mixed-norm weighted $L_p$-estimates for elliptic and parabolic equations/systems with (partially) BMO coefficients in regular or irregular domains.
In this paper we study a rather wide class of quasilinear parabolic problems with nonlinear boundary condition and nonstandard growth terms. It includes the important case of equations with a $p(t,x)$-Laplacian. By means of the localization method and De Giorgi's iteration technique we derive global a priori bounds for weak solutions of such problems. Our results seem to be new even in the constant exponent case.
We prove a new $\mathcal{A}$-caloric approximation lemma compatible with an Orlicz setting. With this result, we establish a partial regularity result for parabolic systems of the type $$ u_{t}- {\rm div} \,a(Du)=0. $$ Here the growth of $a$ is bounded by the derivative of an $N$-function $φ$. The primary assumption for $φ$ is that $tφ''(t)$ and $φ'(t)$ are uniformly comparable on $(0,\infty)$.
Motivated by problems arising in geometric flows, we prove several regularity results for systems of local and nonlocal equations, adapting to the parabolic case a neat argument due to Caffarelli. The geometric motivation of this work comes from recent works arising in the theory harmonic maps with free boundary in particular. We prove Hölder regularity of weak solutions.
For proper minimizers of parabolic variational integrals with linear growth with respect to $|Du|$, we establish a necessary and sufficient condition for $u$ to be continuous at a point $(x_o,t_o)$, in terms of a sufficient fast decay of the total variation of $u$ about $(x_o,t_o)$ (see (1.4) below). These minimizers arise also as {proper} solutions to the parabolic $1$-laplacian equation. Hence, the continuity condition continues to hold for such solutions (§ 3).
Reiterated Periodic Homogenization of Parabolic Monotone Operators with Nonstandard Growth
本文研究导致Orlicz空间的非标准增长单调算子抛物问题的重述周期均匀化，通过重述双尺度收敛方法确定全局和宏观均匀化问题。
Characterizations and properties of solutions to parabolic problems of linear growth
本文研究线性增长抛物问题弱解，通过稳定性结果建立与变分解等价，利用时间磨光和Sobolev逼近逼近BV函数，并证明比较原理、局部有界性及与Anzellotti配对定义的等价性。
This article studies the partial Hölder continuity of weak solutions to certain degenerate parabolic systems whose model is the differentiable parabolic $p(x,t)$-Laplacian system, \begin{equation*}\partial_t u-\operatorname{div}[μ(z)(1+|Du|^2)^{\frac{p(z)-2}{2}}Du]=0,\qquad p(z)\geq2.\end{equation*} Here, the exponential function $p(z)$ satisfies a logarithmic continuity condition. We show that if $μ(z)$ satisfies a certain VMO-type condition, then $u$ is locally Hölder continuous except for a measure zero set.
In this paper we obtain sharp Petrovskii criteria for the p-parabolic equation, both in the degenerate case p>2 and the singular case 1<p<2. We also give an example of an irregular boundary point at which there is a barrier, thus showing that regularity cannot be characterized by the existence of just one barrier.
We prove the Lp,q-solvability of parabolic equations in divergence form with full lower-order terms. The coefficients and non-homogeneous terms belong to mixed Lebesgue spaces with the lowest integrability conditions. In particular, the coefficients for the lower-order terms are not necessarily bounded. We study both the Dirichlet and conormal derivative boundary value problems on irregular domains. We also prove embedding results for parabolic Sobolev spaces, the proof of which is of independent interest.
Large deviations of conservative interacting particle systems, such as the zero range process, about their hydrodynamic limit and their respective rate functions lead to the analysis of the skeleton equation; a degenerate parabolic-hyperbolic PDE with irregular drift. We develop a robust well-posedness theory for such PDEs in energy-critical spaces based on concepts of renormalized solutions and the equation's kinetic form. We establish these properties by proving that renormalized solutions are equivalent to classical weak solutions, extending concepts of [DiPerna, Lions; Ann. Math., 1989], […
Calderón-Zygmund estimates for parabolic systems with $p$-growth and non-divergence data
研究具p增长与非散度数据的非线性抛物系统，提出不要求向量场梯度可微的方法，统一处理奇异与退化情形，建立解梯度的局部更高可积性估计。
We prove the continuity of bounded solutions for a wide class of parabolic equations with $(p,q)$-growth $$ u_{t}-{\rm div}\left(g(x,t,|\nabla u|)\,\frac{\nabla u}{|\nabla u|}\right)=0, $$ under the generalized non-logarithmic Zhikov's condition $$ g(x,t,{\rm v}/r)\leqslant c(K)\,g(y,τ,{\rm v}/r), \quad (x,t), (y,τ)\in Q_{r,r}(x_{0},t_{0}), \quad 0<{\rm v}\leqslant Kλ(r), $$ $$ \quad \lim\limits_{r\rightarrow0}λ(r)=0, \quad \lim\limits_{r\rightarrow0} \frac{λ(r)}{r}=+\infty, \quad \int_{0} λ(r)\,\frac{dr}{r}=+\infty. $$ In particular, our results cover new cases of double-phase parabolic equat…
Entire solutions to the parabolic Monge--Ampère equation with unbounded nonlinear growth in time
本文研究抛物型蒙日-安培方程在时间导数无界情形下的整解，证明了整抛物凸光滑解的存在性并分析其无穷远渐近行为。
Generalized Young Measure Solutions for a Class of Quasilinear Parabolic Equations with Linear Growth
本文利用广义 Young 测度理论将 Young 测度解推广至具线性增长的拟线性抛物型方程，证明了其解的存在唯一性，并证明了对凸抛物变分积分的梯度流而言该解等价于强解。
We study the local regularity of $p$-caloric functions or more generally of $ϕ$-caloric functions. In particular, we study local solutions of non-linear parabolic systems with homogeneous right hand side, where the leading terms has Uhlenbeck structure of Orlicz type. This paper closes the gap of [22] where Liebermann proved that if the gradient of a solution is bounded, it is Hölder continuous. The crucial step is a novel local estimates for the gradient of the solutions, which generalize and improve the pioneering estimates of DiBenedetto and Friedman [12,10] for the $p$-Laplace heat equatio…
We prove global gradient estimates for parabolic $p$-Laplace type equations with measure data, whose model is $$u_t - \textrm{div} \left(|Du|^{p-2} Du\right) = μ\quad \textrm{in} \ Ω\times (0,T) \subset \mathbb{R}^n \times \mathbb{R},$$ where $μ$ is a signed Radon measure with finite total mass. We consider the singular case $$\frac{2n}{n+1} <p \le 2-\frac{1}{n+1}$$ and give possibly minimal conditions on the nonlinearity and the boundary of $Ω$, which guarantee the regularity results for such measure data problems.
In this article we develop a framework for studying parabolic semilinear stochastic evolution equations (SEEs) with singularities in the initial condition and singularities at the initial time of the time-dependent coefficients of the considered SEE. We use this framework to establish existence, uniqueness, and regularity results for mild solutions of parabolic semilinear SEEs with singularities at the initial time. We also provide several counterexample SEEs that illustrate the optimality of our results.
The aim of this paper is to establish a higher integrability result for very weak solutions of certain parabolic systems whose model is the parabolic $p(x,t)$-Laplacian system. Under assumptions on the exponent function $p:Ω_T=Ω\times (0,T)\to\left(\frac{2n}{n+2},2\right]$, it is shown that any very weak solution $u:Ω_T\rightarrow\mathbb{R}^N$ with $|Du|^{p(\cdot)(1-\varepsilon)}\in L^1(Ω_T)$ belongs to the natural energy spaces, i.e. $|Du|^{p(\cdot)}\in L^1_{\operatorname{loc}}(Ω_T)$, provided $ε>0$ is small enough. This extends the main result of [V. Bögelein and Q. Li, Nonlinear Anal., 98 (…
Boundedness through nonlocal dampening effects in a fully parabolic chemotaxis model with sub and superquadratic growth
本文研究了包含次和超二次增长外部源及非局部阻尼反应的趋化模型，证明了在有界不可渗透区域中，只要阻尼效应足够强，细胞就不会随时间出现聚集效应。
Higher integrability for parabolic PDEs with generalized Orlicz growth
针对广义Orlicz增长的抛物型系统，通过(A1)条件统一处理奇异与退化情形，证明梯度的高可积性，涵盖p增长、变指数和双相增长等特例。
Partial regularity for degenerate parabolic systems with general growth via caloric approximations
该研究针对带一般$\varphi$-增长的抛物型方程组，借助$\varphi$-热逼近与改进的$\mathcal{A}$-热逼近（无需经典紧性方法），建立了不依赖方程组退化性的统一部分正则性结果。
This paper studies asymptotic behavior of solutions of a free boundary problem modeling the growth of tumors with two species of cells: proliferating cells and quiecent cells. In previous literatures it has been proved that this problem has a unique stationary solution which is asymptotically stable in the limit case $\varepsilon=0$. In this paper we consider the more realistic case $0<\varepsilon<<1$. In this case, after suitable reduction the model takes the form of a coupled system of a parabolic equation and a hyperbolic system, so that it is more difficult than the limit case $\varepsilon…
Parabolic De Giorgi classes with doubly nonlinear, nonstandard growth: local boundedness under exact integrability assumptions
该研究定义了含非平衡能量估计的抛物型De Giorgi函数类$\mathcal{PDG}$，证明其在奇异抛物算子的三类增长条件下局部有界，次临界情形的结果为全新成果，无需额外可积性条件。
In this paper, we obtain $C^{1,α}$ estimates for weak solutions of certain quasilinear parabolic equations satisfying nonstandard growth conditions, the prototype examples being $$u_t - \text{div} (|\nabla u|^{p-2} \nabla u + a(t)|\nabla u|^{q-2} \nabla u) = 0,$$ $$u_t - \text{div} (|\nabla u|^{p(t)-2} \nabla u) = 0.$$ under the assumption that the solutions a priori have bounded gradient. We build on the recently developed scaling and covering argument which allows us to consider the singular and degenerate cases in a uniform manner and with minimal regularity requirements on the phase switch…
Parabolic equations with non-standard growth and measure or integrable data
研究了带 Dirichlet 边界条件及测度或 $L^1$ 数据的抛物型偏微分方程，在变指数 $p$ 满足空间有界及 log-Hölder 连续但时间上无平滑性假设的条件下，证明了弱解的存在性及熵解的存在性与唯一性。
It has been well established that, in attraction-repulsion Keller-Segel systems of the form\begin{equation*} \left\{ \begin{aligned} u_t &= Δu - χ\nabla \cdot (u\nabla v) + ξ\nabla \cdot (u\nabla w), \\ τv_t &= Δv + αu - βv,\\ τw_t &= Δw + γu - δw \end{aligned} \right. \end{equation*} in a smooth bounded domain $Ω\subseteq \mathbb{R}^n$, $n\in\mathbb{N}$, with Neumann boundary conditions and parameters $χ, ξ\geq 0$, $α,β,γ,δ> 0$ and $τ\in \{0,1\}$, finite-time blow-up can be ruled out in many scenarios given sufficiently smooth initial data if the repulsive chemotaxis is sufficiently stronger …
We prove higher integrability of the spatial gradient of weak solutions to parabolic systems with $ϕ$-growth, where $φ=φ(t)$ is a general Orlicz function. The parabolic systems need be neither degenerate nor singular. Our result is a generalized version of the one of J. Kinnunen and J. Lewis [Duke Math. J. 102 (2000), no. 2, 253--271] for the parabolic $p$-Laplace systems.
In this paper, we consider a model with tumor microenvironment involving nutrient density, extracellular matrix and matrix-degrading enzymes, which satisfy a coupled system of PDEs with a free boundary. For this coupled parabolic-hyperbolic free boundary problem, we prove that there is a unique radially symmetric solution globally in time. The stationary problem involves an ODE system which is transformed into a singular integro-differential equation. We establish a well-posed theorem for such general types of equations by the shooting method; the theorem is then applied to our problem for the…
We consider a parabolic-elliptic system of partial differential equations with chemotaxis and logistic growth given by the system $$ \left\{ \begin{array}{l} u_t -Δ(u γ(v)= μu(1-u), \\ - Δv +v=u, \end{array} \right. $$ under Neumann boundary conditions and appropriate initial data in a bounded and regular domain $Ω$ of $\R^N$ (for $N \geq 1)$, where $γ\in C^3([0, \infty))$ and satisfies the assumptions $γ(s) > 0$, $γ^{\prime}(s) \leq 0$, $γ^{\prime \prime} (s) \geq 0$, $γ^{\prime \prime \prime}(s) \leq 0$ for any $s \geq 0$ $$-2 γ^{\prime}(s) + γ^{\prime \prime}(s)s \leq μ_0< μ$$ $$\frac{[γ^{\…
Existence and uniqueness of solution to a hyperbolic-parabolic free boundary problem for biofilm growth
本研究针对生物膜生长的双曲-抛物耦合自由边界问题，采用特征线法与不动点策略，借助Green函数转化方程，证明了小时间及全时间解的存在唯一性，并考虑了多种边界条件及其拓展。
$L_p$-estimates for parabolic equations in divergence form with a half-time derivative
本文研究右端含半阶时间导数项的散度型线性抛物方程，在系数仅关于时间或一个空间变量可测的不规则条件下，建立了 Sobolev 空间中解的唯一可解性。
In this paper, we study quasilinear parabolic equations with the nonlinearity structure modeled after the $p(x,t)$-Laplacian on nonsmooth domains. The main goal is to obtain end point Calderón-Zygmund type estimates in the variable exponent setting. In a recent work \cite{byun2016nonlinear}, the estimates obtained were strictly above the natural exponent $p(x,t)$ and hence there was a gap between the natural energy estimates and the estimates above $p(x,t)$ (see \eqref{energy} and \eqref{byunok}). Here, we bridge this gap to obtain the end point case of the estimates obtained in \cite{byun2016…
Boundary symmetry breaking via logistic damping in a chemotaxis-growth system
研究在1D领域内具有对数敏感性的趋化-生长模型的全局稳定性，分析抛物线-抛物线和抛物线-双曲线系统，通过引入动态参考轮廓处理时间依赖的边界数据，证明能量估计、解的有界性和扰动的全局渐进行为。
In this paper we establish the exact growth of the solution of the singular quasilinear p-parabolic obstacle problem near the free boundary from which we deduce its porosity.
We study global-in-time well-posedness and the behaviour and of the solution to Cauchy problem in the classical Keller-Segel system with logistic term \begin{equation*} \left. \aligned \partial_tn-Δn=&-χ\nabla\cdot(n\nabla c)+\la n-μn^2 τ\partial_tc-Δc=&-c+n \endaligned \right\}\quad\text{in}\,\,\,\RR^d\times\RR^+, \end{equation*} where $d\ge 1$, $τ,\, χ,\, μ>0$ and $λ\ge 0$. It's inspired by a previous result \cite[M. Winkler, Commun. Part. Diff. Eq., 35 (2010), 1516-1537]{Win10}, where the global-in-time boundedness of the above Keller-Segel system in smooth \emph{bounded }convex domains is …
Blow-up solutions of parabolic $p$-Laplacian inequalities on locally finite graphs
本文研究了局部有限连通加权图上带 $p$-Laplacian 算子的半线性抛物型不等式的爆破行为，推广比较原理并证明当非线性源增长率超过线性时存在爆破解。
Regularity theory for parabolic systems with Uhlenbeck structure
本文针对具有 $φ$-增长的 Uhlenbeck 型抛物型方程组，在适当增长条件下证明弱解与梯度的局部有界性及梯度的局部 Hölder 连续性，并给出统一处理退化和奇异情形的方法。
Renormalized and entropy solutions to the general nonlinear parabolic equations in Musielak-Orlicz spaces
该研究针对含仅可积数据的一般非线性抛物方程，在含时Musielak-Orlicz空间中通过密度论证证明了重整化解与熵解的存在唯一性及二者等价性，结果覆盖多种增长类型问题。
In this article we establish the exact growth of the solution to the singular quasilinear p-parabolic free boundary problem in non-divergence form near the free boundary from which follows its porosity.
Models of tissue growth are now well established, in particular in relation to their applications to cancer. They describe the dynamics of cells subject to motion resulting from a pressure gradient generated by the death and birth of cells, itself controlled primarily by pressure through contact inhibition. In the compressible regime we consider, when pressure results from the cell densities and when two different populations of cells are considered, a specific difficulty arises from the hyperbolic character of the equation for each cell density, and to the parabolic aspect of the equation for…
We prove boundedness of gradients of solutions to quasilinear parabolic system, the main part of which is a generalization to p-Laplacian and its right hand side's growth depending on gradient is not slower (and generally strictly faster) than p - 1. This result may be seen as a generalization to the classical notion of a controllable growth of right hand side, introduced by Campanato, over gradients of p-Laplacian-like systems. Energy estimates and nonlinear iteration procedure of a Moser type are cornerstones of the used method.
On quasilinear parabolic systems and FBSDEs of quadratic growth
本文使用概率方法为两类具有二次梯度增长的拟线性抛物PDE系统建立先验估计，证明了其经典解的存在性，并由此推断出相应前向-后向随机微分方程解的存在性。
We consider an abstract parabolic problem in a framework of maximal monotone graphs, possibly multi-valued with growth conditions formulated with help of an $x-$dependent $N-$function. The main novelty of the paper consists in the lack of any growth restrictions on the ${N}$--function combined with its anisotropic character, namely we allow the dependence on all the directions of the gradient, not only on its absolute value. This leads us to use the notion of modular convergence and studying in detail the question of density of compactly supported smooth functions with respect to the modular c…
Comparison results for unbounded solutions for a parabolic Cauchy-Dirichlet problem with superlinear gradient growth
本文针对具有超线性梯度增长的抛物型Cauchy-Dirichlet问题，研究其无界解的唯一性，通过比较方法给出结果。
We consider the obstacle problem with two irregular reflecting barriers for the Cauchy-Dirichlet problem for semilinear parabolic equations with measure data. We prove the existence and uniqueness of renormalized solutions of the problem and well as results on approximation of the solutions by the penaliztion method. In the proofs we use probabilistic methods of the theory of Markov processes and the theory of backward stochastic differential equations.
Absence of the Lavrentiev phenomenon for a general class of parabolic double phase problems
本文证明具有Orlicz增长的一般类抛物双相泛函中拉夫连季耶夫现象缺失，将相关理论从幂次增长扩展到广泛Young函数框架，确定了问题对应的时空Orlicz能量类。
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