The scarcity of antimatter in the universe compared to matter is still an open question in physics. While antimatter is known to exist and has been created in laboratories, its abundance in the observable universe is extremely low. The reason for this is not yet fully understood, and it remains an active area of research.
One possible explanation for the observed asymmetry between matter and antimatter is known as baryogenesis. According to current theories, shortly after the Big Bang, there was an equal amount of matter and antimatter in the early universe. However, a tiny imbalance in certain fundamental particle interactions, known as CP-violation, could have resulted in a slight excess of matter over antimatter. As a result, most of the matter and antimatter annihilated each other, leaving behind the small amount of matter we observe today.
Regarding the presence of regions with only antimatter in the universe, it is not currently known if such regions exist on a large scale. In the observable universe, matter and antimatter are typically found in mixed distributions. However, it is worth noting that the current understanding of the universe is limited to what we can observe, and there may be regions beyond our observational reach where antimatter-dominated environments exist.
Further exploration and experimentation in particle physics and cosmology are necessary to gain a deeper understanding of the matter-antimatter asymmetry and the distribution of antimatter in the universe.