Limits on Q-ball size due to gravity

Solitonic scalar field configurations are studied in a theory coupled to gravity. It is found that non-topological solitons, Q-balls, are present in the theory. Properties of gravitationally self coupled Q-balls are studied by analytical and numerical means. Analytical arguments show that, unlike in the typical flat space scenario, the size of Q-balls is ultimately limited by gravitational effects. Even though the largest Q-balls are very dense, their radii are still much larger than the corresponding Schwarzschild radii. Gravity can also act as a stabilising mechanism for otherwise energetically unstable Q-balls.