Extremal function for a sharp Moser-Trudinger type inequality on the upper half space

Sharp Moser-Trudinger type inequalities and their extremal functions play an important role in studying nonlinear PDEs and geometry. We establish a new sharp Moser-Trudinger type inequality in the upper half space in two dimensions and prove the existence of extremal functions for a sharp Moser-Trudinger type inequality under dynamic changes in the unit ball.