Actually, that paper does not address the expanding universe theory, nor does its conclusions invalidate the idea of a non-expanding universe. What that paper concludes is that over time, “through mergers and accretions” the number of galaxies has decreased. They claim there are fewer galaxies now than in the distant past not that they are further away from each other now than in the distant past. They mention that at higher redshift (they are assuming higher redshift equals greater distance) there are more low-mass galaxies than at lower redshift, which leads to their conclusion that low-mass galaxies merged with high-mass galaxies, causing the decrease in the total number of galaxies. That is plausible, but does not have a bearing on the question of whether the universe is expanding. Their paper may actually take away one of the arguments for an expading universe.