Vibrational modes of Q-balls

Understand

We study linear perturbations of classically stable Q-balls in theories admitting analytic solutions.

• Although the corresponding boundary value problem is non-Hermitian, the analysis of perturbations can also be performed analytically in certain regimes.
• We show that in theories with the flat potential, large Q-balls possess soft excitations.
• We also find a specific vibrational mode for Q-balls with a near-critical charge, where the perturbation theory for excitations can be developed.