  The bulk phase behavior of a fluid is typically altered when the fluid is
brought into confinement by the walls of a random porous medium. Inside the
porous medium, phase transition points are shifted, or may disappear
altogether. A crucial determinant is how the walls interact with the fluid
particles. In this work, we consider the situation whereby the walls are
neutral with respect to the liquid and vapor phase. In order to realize the
condition of strict neutrality, we use a symmetric binary mixture inside a
porous medium that interacts identically with both of the mixture species.
Monte Carlo simulations are then used to obtain the phase behavior. Our main
finding is that, in the presence of the porous medium, a liquid-vapor type
transition still occurs, but with critical exponents that deviate from bulk
Ising values. In addition, we observe clear violations of self-averaging. These
findings provide further evidence that random confinement by neutral walls
induces critical behavior of the random Ising model (i.e. Ising models with
dilution type disorder, where the disorder couples to the energy).
