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 the higher order weighted Poincaré inequalities with variable exponents. For these results the crucial part is proving the boundedness of the fractional integral operator on Lebesgue spaces with weighted and variable exponents on spaces of homogeneous type. Moreover, using other techniques, we extend some of these results when the exponent satisfies a jump condition and the weight is in a smaller Muckenhoupt class. Finally, we will use these weighted Poincaré inequalities to establish the existence and uniqueness of a minimizer to the Dirichlet energy integral for a problem involving a degenerate $p(\cdot )$-Laplacian with zero boundary values in Carnot groups.