Simple transitive 2-representations via (co)algebra 1-morphisms Volodymyr Mazorchuk Indiana University Mathematics Journal 2019 text pdf 10.1512/iumj.2019.68.7554 10.1512/iumj.2019.68.7554 en Indiana Univ. Math. J. 68 (2019) 1 - 33 state-of-the-art mathematics http://iumj.org/access/