Lifting of convex functions on Carnot groups and lack of convexity for a gauge function |
| |
Authors: | Andrea Bonfiglioli |
| |
Institution: | 1. Dipartimento di Matematica, Università degli Studi di Bologna, Piazza di Porta San Donato 5, 40126, Bologna, Italy
|
| |
Abstract: | Let ${\mathbb{G}}Let
\mathbbG{\mathbb{G}} be a Carnot group of step r and m generators and homogeneous dimension Q. Let
\mathbbFm,r{\mathbb{F}_{m,r}} denote the free Lie group of step r and m generators. Let also
p:\mathbbFm,r?\mathbbG{\pi:\mathbb{F}_{m,r}\to\mathbb{G}} be a lifting map. We show that any horizontally convex function u on
\mathbbG{\mathbb{G}} lifts to a horizontally convex function u°p{u\circ \pi} on
\mathbbFm,r{\mathbb{F}_{m,r}} (with respect to a suitable horizontal frame on
\mathbbFm,r{\mathbb{F}_{m,r}}). One of the main aims of the paper is to exhibit an example of a sub-Laplacian L=?j=1m Xj2{\mathcal{L}=\sum_{j=1}^m X_j^2} on a Carnot group of step two such that the relevant L{\mathcal{L}}-gauge function d (i.e., d
2-Q
is the fundamental solution for L{\mathcal{L}}) is not h-convex with respect to the horizontal frame {X
1, . . . , X
m
}. This gives a negative answer to a question posed in Danielli et al. (Commun. Anal. Geom. 11 (2003), 263–341). |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|