1. Polynomial-time theory of matrix groups;Babai,2009
2. Learning weighted automata;Balle,2015
3. Mortality for 2×2 matrices is NP-hard;Bell,2012
4. The identity problem for matrix semigroups in SL2(Z) is NP-complete;Bell,2017
5. Reachability problems in quaternion matrix and rotation semigroups;Bell;Inf. Comput.,2008