Basic properties of nonsmooth Hormander's vector fields and Poincare's inequality

Fundamental solutions and local solvability for nonsmooth Hörmander's operators

We consider operators of the form $L=\sum_{i=1}^{n}X_{i}^{2}+X_{0}$ in a bounded domain of R^p where X_0, X_1,...,X_n are nonsmooth Hörmander's vector fields of step r such that the highest order commutators are only Hölder continuous. Applying Levi's parametrix method we construct a local fundamental solution γ for L and provide growth estimates for γ and its first derivatives with respect to the vector fields. Requiring the existence of one more derivative of the coefficients we prove that γ also possesses second derivatives, and we deduce the local solvability of L, constructing, by means o…

Weighted $p(\cdot)$-Poincaré and Sobolev inequality]{Weighted $% p(\cdot )$-Poincaré and Sobolev inequalities for vector fields satisfiying Hörmander's condition and applications

In this paper we will establish different weighted Poincaré inequalities with variable exponents on Carnot-Carathéodory spaces or Carnot groups. We will use different techniques to obtain these inequalities. For vector fields satisfying Hörmander's condition in variable non-isotropic Sobolev spaces, we consider a weight in the variable Muckenhoupt class $% A_{p(\cdot ),p^{\ast }(\cdot )}$, where the exponent $p(\cdot )$ satisfies appropriate hypotheses, and in this case we obtain the first order weighted Poincaré inequalities with variable exponents. In the case of Carnot groups we also set up…

On the lifting and approximation theorem for nonsmooth vector fields

We prove a version of Rothschild-Stein's theorem of lifting and approximation and some related results in the context of nonsmooth Hormander's vector fields for which the highest order commutators are only Holder continuous. The theory explicitly covers the case of one vector field having weight two while the others have weight one.

Weighted multilinear Poincare inequalities for vector fields of Hormander type

As the classical $(p,q)$-Poincaré inequality is known to fail for $0 < p < 1$, we introduce the notion of weighted multilinear Poincaré inequality as a natural alternative when $m$-fold products and $1/m < p$ are considered. We prove such weighted multilinear Poincaré inequalities in the subelliptic context associated to vector fields of Hörmader type. We do so by establishing multilinear representation formulas and weighted estimates for multilinear potential operators in spaces of homogeneous type.

Hörmander向量场对应的次椭圆$p$-Laplacian谱问题

Subelliptic $p$-Laplacian spectral problem for Hörmander vector fields

该研究利用变分方法探究光滑Hörmander向量场导出的次椭圆$p$-Laplacian谱问题，得到最小特征值的相关性质与特征函数的正则性，还顺带确定了对应$L^p$-Poincaré-Friedrichs不等式的最佳常数。

A Nash Type result for Divergence Parabolic Equation related to Hormander's vector fields

In this paper we consider the divergence parabolic equation with bounded and measurable coefficients related to Hormander's vector fields and establish a Nash type result, i.e., the local Holder regularity for weak solutions. After deriving the parabolic Sobolev inequality, (1,1) type Poincaré inequality of Hormander's vector fields and a De Giorgi type Lemma, the Holder regularity of weak solutions to the equation is proved based on the estimates of oscillations of solutions and the isomorphism between parabolic Campanato space and parabolic Holder space. As a consequence, we give the Ha…