Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. In theoretical physics, Q-ball refers to a type of non-topological soliton. A soliton is a localized field configuration that is stable it cannot spread out and dissipate. In the case of a non-topological soliton, the stability is guaranteed by a conserved charge: the soliton has lower energy per unit charge than any other configuration. (In physics, charge is often represented by the letter "Q", and the soliton is spherically symmetric, hence the name.) A Q-ball arises in a theory of bosonic particles, when there is an attraction between the particles. Loosely speaking, the Q-ball is a finite-sized "blob" containing a large number of particles. The blob is stable against fission into smaller blobs, and against "evaporation" via emission of individual particles, because, due to the attractive interaction, the blob is the lowest-energy configuration of that number of particles. (This is analogous to the fact that Nickel-62 is the most stable nucleus because it is the most stable configuration of neutrons and protons, however Nickel-62 is not a Q-ball, in part because neutrons and protons are fermions not bosons.)
