When you bring the paper up it indicates that they are talking about a lack of density in a region, not a repulsive force.
You can treat it as a repulsive force, in the same way you can treat the absence of an electron in a semiconductor as a particle with a positive charge (a ‘hole’). With matter density from the bulk of the rest of the universe all around it, the gravity of that matter pulls things near the edge of the low density region away from it and this is functionally similar to repulsion away from the void. The paper finds that the flow away from the low density region towards the generalized rest of the bulk universe is about as important for our galaxy’s motion as the attraction towards the local overdensity of the various nearby attractors.
When you bring the paper up it indicates that they are talking about a lack of density in a region, not a repulsive force.
You can treat it as a repulsive force, in the same way you can treat the absence of an electron in a semiconductor as a particle with a positive charge (a ‘hole’). With matter density from the bulk of the rest of the universe all around it, the gravity of that matter pulls things near the edge of the low density region away from it and this is functionally similar to repulsion away from the void. The paper finds that the flow away from the low density region towards the generalized rest of the bulk universe is about as important for our galaxy’s motion as the attraction towards the local overdensity of the various nearby attractors.