  We construct global dissipative solutions on the torus of dimension at most
three of the defocusing isothermal Euler-Langevin-Korteweg system, which
corresponds to the Euler-Korteweg system of compressible quantum fluids with an
isothermal pressure law and a linear drag term with respect to the velocity. In
particular, the isothermal feature prevents the energy and the BD-entropy from
being positive. Adapting standard approximation arguments we first show the
existence of global weak solutions to the defocusing isothermal
Navier-Stokes-Langevin-Korteweg system. Introducing a relative entropy function
satisfying a Gronwall-type inequality we then perform the inviscid limit to
obtain the existence of dissipative solutions of the Euler-Langevin-Korteweg
system.
