Q-balls in K-field theory

We study the existence and stability of Q -balls in noncanonical scalar field theories, K(I phi I2, X), where phi is the complex scalar field and Xis the kinetic term. We extend the Vakhitov-Kolokolov stability criterion to K -field theories. We derive the condition for the perturbations to have a well-posed Cauchy problem. We find that K,X > 0 and K,X + XK,XX > 0 are necessary but not sufficient conditions. The perturbations define a strongly hyperbolic system if (K,X - 2002K,XX)(K,X + 2 omega 202K,X X) > 0. For all modifications studied, we found that perturbations propagate at a speed different from light. Generically, the noncanonical scalar field can lower the charge and energy of the Q -ball and therefore improves its stability.

Automated summary

We studied the existence and stability of Q-balls in noncanonical scalar field theories. We extended the Vakhitov-Kolokolov stability criterion to K-field theories and derived the condition for well-posed Cauchy problem of perturbations. We found that K,X > 0 and K,X + XK,XX > 0 are necessary but not sufficient conditions, and that perturbations define a strongly hyperbolic system if (K,X - 2002K,XX)(K,X + 2 omega 202K,X X) > 0. The noncanonical scalar field can lower the charge and energy of the Q-ball, improving its stability.