Contact interactions always lead to attractive behavior. Arguments are presented to show why a repulsive interacting system, e.g. Bose gases, cannot be described by contact interactions and corresponding treatments are possibly obscured by the appearance of bound states. The usually used cut-offs are identified as finite range parameters. © 2009 Elsevier B.V. All rights reserved.
Morawetz, K., & Männel, M. (2010). Impossibility to describe repulsion with contact interaction. Physics Letters, Section A: General, Atomic and Solid State Physics, 374(4), 644–646. https://doi.org/10.1016/j.physleta.2009.11.043