Nonlinear causality of Israel-Stewart theory with diffusion
This paper establishes the first fully nonlinear causality constraints for Israel-Stewart theory with energy and number diffusion in 3+1 dimensions, revealing distinct physical behaviors in Landau and Eckart frames that are missed by linearized approaches and demonstrating that these constraints allow for spacelike baryon currents in the Landau frame while preserving the dominant energy condition in the Eckart frame.