Noncommutative harmonic analysis on semigroup and ultracontractivity Xiao XiongXiao Xiong Indiana University Mathematics Journal 2017 text pdf 10.1512/iumj.2017.66.6221 10.1512/iumj.2017.66.6221 en Indiana Univ. Math. J. 66 (2017) 1921 - 1947 state-of-the-art mathematics http://iumj.org/access/