Name Jung Hoon Lee Chonbuk National University Session Jan 11 13:50~14:30 E11-103 Critical Heegaard surfaces obtained by amalgamation Critical surfaces are defined by Bachman as topological index two surfaces, generalizing incompressible surfaces and strongly irreducible surfaces. In this talk we give a condition to obtain critical Heegaard surfaces by amalgamation. As a special case, we obtain critical Heegaard surfaces by boundary stabilization. It gives critical Heegaard surfaces of non-minimal genus, for $3$-manifolds which do not admit distinct Heegaard splittings (up to isotopy). 103-1-11/8EAS_jhlee.pdf