On the best constant for the Friedrichs-Knapp-Stein inequality in free nilpotent Lie groups of step two and applications to subelliptic PDE
The authors find in the paper the best constant for the Friederichs-Knapp-Stein inequality relative to the free nilpotent group of step two with \(2n\) generators and use the result to prove the second-order differentiability of subelliptic \(p\)-harmonic functions for \(p\) in a suitable interval.
scientific article; zbMATH DE number 5160938
scientific article