How does dark energy slow the formation of galaxies and galaxy clusters?

Dark energy acts as a gravitationally repulsive force that opposes the attractive pull of gravity, which is the primary driver for the formation of large-scale structures like galaxies and clusters of galaxies through gravitational instabilities.1

Because dark energy is gravitationally repulsive, its dominance in the universe accelerates the expansion of space. This accelerated expansion effectively works against gravity, which seeks to pull matter together to form structures. As dark energy became the dominant component of the universe in the last few billion years, it began to retard the growth of these structures by pulling matter apart faster than gravity could coalesce it. Consequently, this process has prevented the formation of additional galaxies and clusters that might have otherwise developed in a universe without such a repulsive force.12

In essence, while gravity promotes the clustering of matter, dark energy acts as a counteracting influence that stretches the fabric of the universe, thereby limiting the rate and extent at which large-scale cosmic structures can form.1