We study the unconditional stability of implicit-explicit backward difference formula (BDF) methods applied to Dahlquist's first test equation. This can be viewed as an attempt to extend the well-known A(q )-stability concept to implicit-explicit multistep methods.

G. Akrivis obtained his PhD in 1983 at the University of Munich, Germany. From 1984 until 1995 he was Assistant and Associate Professor at the Department of Mathematics of the University of Crete, Greece. From 1995 until 2018 he was Professor at the Department of Computer Science and Engineering of the University of Ioannina, Greece. Since 2018 he is Emeritus Professor. He taught as a Visiting Professor at the University of Tennessee, Knoxville, USA, at the University of Cyprus, and at the Huazhong University of Science and Technology, Wuhan, China. His research focuses on numerical methods for evolution partial differential equations, mainly of parabolic type.