Wojciech Górny
We formulate and study the nonlocal and local least gradient problem, which is the Dirichlet problem for the 1-Laplace operator, in a quite natural setting of Carnot groups. We study the passage from the nonlocal problem to the local problem as the range of the interaction goes to zero; to do this, we first prove a total variation estimate of independent interest.
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In this paper we prove an invariant Harnack inequality on Carnot-Carathéodory balls for fractional powers of sub-Laplacians in Carnot groups. The proof relies on an "abstract" formulation of a technique recently introduced by Caffarelli and Silvestre. In addition, we write explicitly the Poisson kernel for a class of degenerate subelliptic equations in product-type Carnot groups.
Let $1<p \leq \infty$. We provide an asymptotic characterization of continuous viscosity solutions $u$ of the normalized $p$-Laplacian $Δ_{p\,\mathbb{G}}^N u=0$ in any Carnot group $\mathbb{G}$.
The fractional powers of the sub-Laplacian in Carnot groups through an analytic continuation
本文通过解析延拓构造卡诺群中亚拉普拉斯算子的分数次幂，刻画海森堡群中该算子的幂次并计算热核k阶矩，为相关分析提供新方法与结果。
In this note, we establish a new Carleman estimate with singular weights for the sub-Laplacian on a Carnot group $\mathbb G$ for functions satisfying the discrepancy assumption in (2.16) below. We use such an estimate to derive a sharp vanishing order estimate for solutions to stationary Schrödinger equations.
In this manuscript, we provide a point-wise estimate for the $3$-commutators involving fractional powers of the sub-Laplacian on Carnot groups of homogeneous dimension $Q$. This can be seen as a fractional Leibniz rule in the sub-elliptic setting. As a corollary of the point-wise estimate, we provide an $(L^{p},L^{q})\to L^{r}$ estimate for the commutator, provided that $\frac{1}{r}=\frac{1}{p}+\frac{1}{q}-\fracα{Q}$.
Let $G$ be a Carnot group. We study nonlocal diffusion equations in a domain $Ω$ of $G$ of the form $$ u_t^ε(x,t)=\int_{G}\frac{1}{ε^2}K_ε(x,y)(u^ε(y,t)-u^ε(x,t))\,dy, \qquad x\in Ω$$ with $u^ε=g(x,t)$ for $x\notinΩ$. For appropriate rescaled kernel $K_ε$ we prove that solutions $u^ε$, when $ε\rightarrow0$, uniformly approximate the solution of different local Dirichlet problem in $G$. The key tool used is the Taylor series development for a function defined on a Carnot group.
In this paper we prove Schauder estimates at the boundary for sub-Laplacian type operators in Carnot groups. While internal Schauder estimates have been deeply studied, up to now subriemannian estimates at the boundary are known only in the Heisenberg groups. The proof of these estimates in the Heisenberg setting, due to Jerison, is based on the Fourier transform technique and can not be repeated in general Lie groups. After the result of Jerison no new contribution to the boundary problem has been provided. In this paper we introduce a new approach, which allows to built a Poisson kernel star…
We propose the analogues of boundary layer potentials for the sub-Laplacian on homogeneous Carnot groups/stratified Lie groups and prove continuity results for them. In particular, we show continuity of the single layer potential and establish the Plemelj type jump relations for the double layer potential. We prove sub-Laplacian adapted versions of the Stokes theorem as well as of Green's first and second formulae on homogeneous Carnot groups. Several applications to boundary value problems are given. As another consequence, we derive formulae for traces of the Newton potential for the sub-Lap…
We prove the local minimality of halfspaces in Carnot groups for a class of nonlocal functionals usually addressed as nonlocal perimeters. Moreover, in a class of Carnot groups in which the De Giorgi's rectifiability Theorem holds, we provide a lower bound for the $Γ$-liminf of the rescaled energy in terms of the horizontal perimeter.
Based on a variant of the frequency function approach of Almgren([Al]), we establish an optimal upper bound on the vanishing order of solutions to stationary Schrödinger equations associated to sub-Laplacian on Carnot groups of arbitrary step. Such bound provides a quantitative form of strong unique continuation and can be thought of as an analogue of the recent results of Bakri and Zhu for the standard Laplacian.
We consider sub-Laplacians in open bounded sets in a homogeneous Carnot group and study their spectral properties. We prove that these operators have a pure point spectrum, and prove the existence of the spectral gap. In addition, we give applications to the small ball problem for a hypoelliptic Brownian motion and the large time behavior of the heat content in a regular domain.
Let G be a Carnot group with homogeneous dimension Q larger than 2 and let L be a sub-Laplacian on G. We prove that the critical dimension for removable sets of Lipschitz L-harmonic functions is Q-1. Moreover we construct self-similar sets with positive and finite (Q-1) dimensional Hausdorff measure which are removable.
On potentials for sub-Laplacians and geometric applications
本文提出了一种在同构卡拉尼集团中利用几何完备性估计极集哈代维度的新方法，并应用于CR几何等领域。
In this note we prove the following theorem in any Carnot group of step two $\mathbb{G}$: \[ \underset{s\nearrow 1/2}{\lim} (1 - 2s) \mathfrak P_{H,s}(E) = \frac{4}{\sqrt π}\ \mathfrak P_H(E). \] Here, $\mathfrak P_H(E)$ represents the horizontal perimeter of a measurable set $E\subset \mathbb{G}$, whereas the nonlocal horizontal perimeter $\mathfrak P_{H,s}(E)$ is a heat based Besov seminorm. This result represents a dimensionless sub-Riemannian counterpart of a famous characterisation of Bourgain-Brezis-Mironescu and Dávila.
In this paper we shall investigate the nonexistence of positive solutions for the following nonlinear parabolic partial differential equation:\[ \begin{cases} \frac{\partial u}{\partial t}= Δ_{\mathbb{G},p}u+V(x)u^{p-1} & \text{in}\quad Ω\times (0, T), \quad 1<p<2, u(x,0)=u_{0}(x)\geq 0 & \text{in} \quadΩ, u(x,t)=0 & \text{on}\quad \partialΩ\times (0, T) \end{cases} \] where $ Δ_{\mathbb{G},p}$ is the $p$-sub-Laplacian on Carnot group $ \mathbb{G}$ and $V\in L_{\text{loc}}^1(Ω)$.
We provide a new characterization of homogeneous Besov and Sobolev spaces in Carnot groups using the fractional heat kernel and Poisson kernel. We apply our results to study commutators involving fractional powers of the sub-Laplacian.
We show how nonlocal boundary conditions of Robin type can be encoded in the pointwise expression of the fractional operator. Notably, the fractional Laplacian of functions satisfying homogeneous nonlocal Neumann conditions can be expressed as a regional operator with a kernel having logarithmic behaviour at the boundary.
We introduce a new notion of Almgren's frequency which is adapted to solutions of a sub-Laplacian (harmonic functions) on a Carnot group of arbitrary step $\bG$. With this notion we investigate some new functionals associated with the frequency, and obtain monotonicity formulas for the relevant harmonic functions, or for the solutions of a closely connected class of degenerate second order operators of Baouendi type. The results proved in this paper provide some new insight into the deep link existing between the growth properties of the frequency, and the local and global structure of the rel…
In this paper we give necessary and sufficient conditions for the existence of solutions to quasilinear equations of Lane--Emden type with measure data on a Carnot group $\mathbb G$ of arbitrary step. The quasilinear part involves operators of the $p$-Laplacian type $Δ_{\mathbb G,\,p}\,$, $1<p<\infty$. These results are based on new a priori estimates of solutions in terms of nonlinear potentials of Th. Wolff's type. As a consequence, we characterize completely removable singularities, and prove a Liouville type theorem for supersolutions of quasilinear equations with source terms which has be…
Equivalence of sub-Laplacian on Polarized groups
本研究刻画了次黎曼李群间与次拉普拉斯算子可交换的光滑映射，证明其为次黎曼淹没映射，还明确了Carnot群中次拉普拉斯算子可决定次黎曼结构，澄清了相关前期分析。
In the present paper we study the existence of solutions for some nonlocal problems involving the p(x)-Laplacian operator. The approach is based on a new sub-supersolution method
In this work we introduce volume constraint problems involving the nonlocal operator $(-Δ)_δ^{s}$, closely related to the fractional Laplacian $(-Δ)^{s}$, and depending upon a parameter $δ>0$ called horizon. We study the associated linear and spectral problems and the behavior of these volume constraint problems when $δ\to0^+$ and $δ\to+\infty$. Through these limit processes on $(-Δ)_δ^{s}$ we derive spectral convergence to the local Laplacian and to the fractional Laplacian as $δ\to 0^+$ and $δ\to +\infty$ respectively, as well as we prove the convergence of solutions of these problems to sol…
In the present paper we study the existence of solutions for a class of nonlocal system involving the p(x)-Laplacian operator. The approach is based on a new sub-supersolution result.
In the sub-Riemannian setting of Carnot groups, this work investigates a-priori estimates and Liouville type theorems for solutions of coercive, quasilinear differential inequalities of the type $$ Δ_{\mathbb{G}}^φu \ge b(x) f(u) l(|\nabla u|). $$ Prototype examples of $Δ_{\mathbb{G}}^φ$ are the (subelliptic) $p$-Laplacian and the mean curvature operator. The main novelty of the present paper is that we allow a dependence on the gradient $l(t)$ that can vanish both as $t \rightarrow 0^+$ and as $t \rightarrow +\infty$. Our results improve on the recent literature and, by means of suitable coun…
We prove an optimal reverse Poincaré inequality for the heat semigroup generated by the sub-Laplacian on a Carnot group of any step. As an application we give new proofs of the isoperimetric inequality and of the boundedness of the Riesz transform in Carnot groups.
In this paper, we study Mountain Pass Characterization of the second eigenvalue of the operator $-\De_p u -\De_{J,p}u$ and study shape optimization problems related to these eigenvalues.
A local and nonlocal coupling model involving the $p$-Laplacian
本文提出一种结合局部和非局部 $p$-拉普拉斯算子的耦合模型，并通过能量泛函的直接最小化证明了解的存在性和唯一性。
In this paper we study the eigenvalue problems for a nonlocal operator of order $s$ that is analogous to the local pseudo $p-$Laplacian. We show that there is a sequence of eigenvalues $λ_n \to \infty$ and that the first one is positive, simple, isolated and has a positive and bounded associated eigenfunction. For the first eigenvalue we also analyze the limits as $p\to \infty$ (obtaining a limit nonlocal eigenvalue problem analogous to the pseudo infinity Laplacian) and as $s\to 1^-$ (obtaining the first eigenvalue for a local operator of $p-$Laplacian type). To perform this study we have to …
On the comparison principle for a nonlocal infinity Laplacian
本文通过比较原理证明了非局部无穷拉普拉斯方程在有界区域上粘性解的唯一性。
Nonlocal Dirichlet problems involving the Logarithmic $p$-Laplacian
本文研究了非局部狄利克雷问题中对数$p$-拉普拉斯算子的极小特征值存在性，并利用$p$-对数赛博利夫不等式证明了新存在性结果。
Symmetry of solutions to nonlocal Neumann problems with the fractional Laplacian in half spaces
本文针对半空间中带非局部Neumann边界条件的分数阶拉普拉斯方程（含方程组），通过建立衰减原理和窄区域原理，结合移动平面法，首次证明了衰减解的对称性与单调性。
A supercritical nonlocal Neumann problem involving non-homogeneous fractional Laplacian
研究外部Neumann条件下分数阶g-Laplace算子支配的非局部非标准增长问题，利用分数阶Orlicz-Sobolev空间性质与非光滑泛函变分原理，证明正非减径向解的存在性。
Inequalities between Dirichlet and Neumann eigenvalues on Carnot groups
本文证明Carnot群开集上次Laplacian算子的第j个Dirichlet特征值大于第(j+1)个Neumann特征值，推广了Euclidean与Heisenberg情形的早期结果。
Nonlocal elliptic equations involving logarithmic Laplacian: Existence, non-existence and uniqueness results
本文研究涉及对数拉普拉斯算子的非局部椭圆方程的存在性、非存在性与唯一性，证明Pohozaev恒等式和Díaz-Saa型不等式，并揭示加权非局部问题的极小能量解在超线性和次线性增长下分别收敛于Brézis-Nirenberg型和逻辑型极限问题的解。
In this paper we consider a non-local problem for a Laplace operator in a multidimensional bounded symmetric domain. The investigated problem is an analogue of the classical periodic boundary value problems in the case of non-rectangular domain. We prove self-adjointness of the problem and show a method of constructing eigenfunctions. We obtain an analogue of the Rayleigh type inequality and some spectral inequalities for the first eigenvalue of the nonlocal problem.
The best constant in the G-N inequality for the mixed local and Nonlocal Laplacian
本文研究混合局部和非局部拉普拉斯算子的G-N不等式最佳常数，提出创新方法证明最优常数的优化器为基态解，并确定最佳常数。
In this note we introduce some nonlinear extremal nonlocal operators that approximate the, so called, truncated Laplacians. For these operators we construct representation formulas that lead to the construction of what, with an abuse of notation, could be called "fundamental solutions". This, in turn, leads to Liouville type results. The interest is double: on one hand we wish to "understand" what is the right way to define the nonlocal version of the truncated Laplacians, on the other, we introduce nonlocal operators whose nonlocality is on one dimensional lines, and this dramatically changes…
Existence and uniqueness of weak solutions to a parabolic nonlocal 1-Laplacian equation
本文研究抛物型非局部1-Laplacian方程，采用Rothe时间离散化方法证明了其弱解的存在性与唯一性，并得出弱解在时间上保持1/2-Hölder连续性的新结论。
Mean value formulas are of great importance in the theory of partial differential equations: many very useful results are drawn, for instance, from the well known equivalence between harmonic functions and mean value properties. In the nonlocal setting of fractional harmonic functions, such an equivalence still holds, and many applications are now-days available. The nonlinear case, corresponding to the $p$-Laplace operator, has also been recently investigated, whereas the validity of a nonlocal, nonlinear, counterpart remains an open problem. In this paper, we propose a formula for the \emph{…
Comparing three possible hypoelliptic Laplacians on the 5-dimensional Cartan group via div-curl type estimates
本文在具有2个生成元的3步自由Carnot群（5维Cartan群）上提出三种亚椭圆Hodge-Laplacian定义，并比较它们在获得精确div-curl型不等式方面的适用性，以克服Rumin外微分非齐次性带来的困难。
We study $s$-fractional $p$-Laplacian type equations with discontinuous kernel coefficients in divergence form to establish $W^{s+σ,q}$ estimates for any choice of pairs $( σ,q)$ with $q\in(p,\infty)$ and $σ\in\left(0,\min\left\{\frac{s}{p-1},1-s\right\}\right)$ under the assumption that the associated kernel coefficients have small BMO seminorms near the diagonal. As a consequence, we find in the literature an optimal fractional Sobolev regularity of such a non-homogeneous nonlocal equation when the right-hand side is presented by a suitable fractional operator. Our results are new even in th…
The aim of the present paper is to study existence results of minimizers of the critical fractional Sobolev constant on bounded domains. Under some values of the fractional parameter we show that the best constant is achieved. If moreover the underlying domain is a ball, we obtain positive radial minimizers for all possible values of the fractional parameter in higher dimension, while we impose a positive mass condition in low dimension.
In this paper, we develop a direct {\em blowing-up and rescaling} argument for a nonlinear equation involving the fractional Laplacian operator. Instead of using the conventional extension method introduced by Caffarelli and Silvestre, we work directly on the nonlocal operator. Using the integral defining the nonlocal elliptic operator, by an elementary approach, we carry on a {\em blowing-up and rescaling} argument directly on nonlocal equations and thus obtain a priori estimates on the positive solutions for a semi-linear equation involving the fractional Laplacian. We believe that the ideas…
On an evolutionary equation involving the nonlocal infinity Laplacian
研究非局部无穷拉普拉斯算子的演化方程，在柱体区域上利用 Perron 方法证明 Dirichlet 问题解的存在性和唯一性。
Critical Ambrosetti-Prodi type problems on Carnot groups
本文研究了Carnot群上涉及子拉普拉斯算子的临界Ambrosetti-Prodi问题，探讨了参数λ<λ₁和λ>λ₁时解的存在性和多重性，以及在λ=λ₁时共振情况下的解的存在性及特征。
Nonlocal gradient, the nonlocal Laplacian and maximum principles
研究非局部\(\rho -\)拉普拉斯算子，通过确定核\(\rho\)条件，建立其与积分 - 微分椭圆算子类的联系，并在更弱\(\rho\)条件下建立最大值和比较原理，涵盖更广泛算子族，且对核假设最小。
We study a class of nonlocal reaction-diffusion equations with a harvesting term where the nonlocal operator is given by a Bernstein function of the Laplacian. In particular, it includes the fractional Laplacian, fractional relativistic operators, sum of fractional Laplacians of different order etc. We study existence, uniqueness and multiplicity results of the solutions to the steady state equation. We also consider the parabolic counterpart and establish the long time asymptotic of the solutions. Our proof techniques rely on both analytic and probabilistic arguments.
The concentration-compactness principle for the nonlocal anisotropic $p$-Laplacian of mixed order
该研究针对一类具有正交各向异性结构、可积指数与可微阶数互异的非局部算子，推广集中紧性原理，证明了其Sobolev商极小元的存在性，并得到对应临界问题存在非平凡非负解的结论。
On the solutions of nonlocal 1-Laplacian equation with $L^1$-data
本文研究带非负 $L^1$-数据和 Dirichlet 边界条件的非局部 1-Laplacian 方程，通过分析非局部 $p$-Laplacian 重整化解在 $p\to1^+$ 时的渐近行为，给出合适的解定义并证明极限函数为原方程的解。
On a family of fully nonlinear integro-differential operators: From fractional Laplacian to nonlocal Monge-Ampère
本文提出了一类介于分数阶拉普拉斯算子和非局部 Monge-Ampère 之间的完全非线性积分微分算子，利用重排技术给出了其表示公式与最优传输的联系，并证明了全空间中全局 Poisson 问题解的存在性、唯一性与 $C^{1,1}$-正则性。
Given a Carnot-Carathéodory space $\Om \sub \R^n$ with associated vector fields $X=\{X_1,...,X_m\}$, we derive the subelliptic $\infty$-Laplace system for mappings $u : \Om \larrow \R^N$, which reads \[ \label{1} \De^X_\infty u \, :=\, \Big(Xu \ot Xu + \|Xu\|^2 [Xu]^\bot \ot I \Big) : XX u\, = \, 0 \tag{1} \] in the limit of the subelliptic $p$-Laplacian as $p\ri \infty$. Here $Xu$ is the horizontal gradient and $[Xu]^\bot$ is the projection on its nullspace. Next, we identify the Variational Principle characterizing \eqref{1}, which is the "Euler-Lagrange PDE" of the supremal functional \[ \l…
In this paper we study nonlocal problems that are analogous to the local ones given by the Laplacian or the p-Laplacian with dynamical boundary conditions. We deal both with smooth and with singular kernels and show existence and uniqueness of solutions and study their asymptotic behaviour as t goes to infinity.
Mixed local and nonlocal laplacian without standard critical exponent for Lane-Emden equation
本文研究了结合经典与分数阶拉普拉斯算子的混合Lane-Emden方程，利用Lyapunov-Schmidt型约化方法证明在略低于临界Sobolev指数时解的存在性，揭示了局部与非局部算子相互作用导致传统临界指数缺失，首次给出临界指数对偶性失效的椭圆算子实例。
We investigate bubbling solutions for the nonlocal equation \[ A_Ω^s u =u^p,\ u >0 \quad \mbox{in } Ω, \] under homogeneous Dirichlet conditions, where $Ω$ is a bounded and smooth domain. The operator $A_Ω^s$ stands for two types of nonlocal operators that we treat in a unified way: either the spectral fractional Laplacian or the restricted fractional Laplacian. In both cases $s \in (0,1)$ and the Dirichlet conditions are different: for the spectral fractional Laplacian, we prescribe $u=0$ on $\partial Ω$ and for the restricted fractional Laplacian, we prescribe $u=0$ on $\mathbb R^n \setminus…
In this paper we study the Dirichlet eigenvalue problem $$ -Δ_p u-Δ_{J,p}u =λ|u|^{p-2}u \quad \text{ in } Ω,\quad u=0 \quad\text{ in } Ω^c=\mathbb{R}^N\setminusΩ. $$ Here $Δ_p u$ is the standard local $p-$Laplacian, $Δ_{J,p}u$ is a nonlocal, $p-$homogeneous operator of order zero and $Ω$ is a bounded domain in $\mathbb{R}^N$. We show that the first eigenvalue (that is isolated and simple) satisfies $(λ_1)^{1/p}\to Λ$ as $p\to\infty$ where $Λ$ can be characterized in terms of the geometry of $Ω$. We also find that the eigenfunctions converge, $u_\infty=\lim_{p\to\infty} u_p$, and find the limit…
Optimal boundary regularity for mixed local and nonlocal equations
本文研究了混合局部和非局部方程的最优边界正则性，通过加权霍尔德空间和固定点论证，提供精确的估计并用反例证明其最优性。
Existence and multiplicity of solutions involving the $p(x)$-Laplacian equations: On the effect of two nonlocal terms
研究一类含双非局部项的$p(x)$-基尔霍夫问题，利用变分方法证明两个非平凡解及无穷多解的存在性，推广了已有结果。
In this PhD thesis, we deal with problems related to nonlocal operators, in particular to the fractional Laplacian and to some other types of fractional derivatives (the Caputo and the Marchaud derivatives). We make an extensive introduction to the fractional Laplacian, we present some related contemporary research results and we add some original material. Indeed, we study the potential theory of this operator, introduce a new proof of Schauder estimates using the potential theory approach, we study a fractional elliptic problem in $\mathbb{R}^n$ with convex nonlinearities and critical growth…
Polar Coordinates in Carnot groups II
本文研究 Carnot 群的可极化性，证明了若 Carnot 群支持具有适当性质的水平极坐标系，则该群是可极化的，从而确立了该性质的充要条件。
Refined Strichartz Estimates for sub-Laplacians in Heisenberg and $H$-type groups
本文利用Fourier限制与谱投影估计，将Heisenberg群上Schrödinger方程的Strichartz估计推广至非径向数据及$H$-型群，并涵盖波动方程。
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