For the ball used in billiards, see cue ball."Q ball" is also the name of the Q sensor module in the Apollo spacecraft launch escape system. In theoretical physics, Q-ball refers to a type ofnon-topological soliton.A soliton is a localized field configurationthat 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 solitonhas lower energy per unit charge than any other configuration.(In physics, charge is often represented by the letter "Q", and the solitonis spherically symmetric, hence the name.) Constructing a Q-ball In its simplest form,a Q-ball is constructed in a field theory of a complex scalar field phi ,in which Lagrangian is invariant under a global U(1) symmetry. The Q-ball solution is a state which minimizes energy while keeping the charge Q associated with the global U(1)