Q-stars in anti de Sitter spacetime

We study q-stars with various symmetries in anti de Sitter spacetime in 3+1 dimensions. Comparing with the case of flat spacetime, we find that the value of the field at the center of the soliton is larger when the other parameters show a more complicated behavior. We also investigate their phase space when the symmetry is local and the effect of the charge to its stability.Comment: 32 pages, 19 figures, to appear in Gen. Rel. Gra

EYM equations in the presence of q-stars is scalar-tensor gravitational theories

We study Einstein-Yang-Mills equations in the presence of a gravitating non-topological soliton field configuration consisted of a Higgs doublet, in Brans-Dicke and general scalar-tensor gravitational theories. The results of General Relativity are reproduced in the $\omega_{\textrm{BD}},\omega_0\to\infty$ limit. The numerical solutions correspond to a soliton star with a non-abelian gauge field. We study the effects of the coupling constant, the frequency of the Higgs field and the Brans-Dicke field on the soliton parametersComment: 17 pages, to appear in Phys. Rev.

Q-stars in scalar-tensor gravitational theories in extra dimensions

We present Jordan-Brans-Dicke and general scalar-tensor gravitational theory in extra dimensions in an asymptotically flat or anti de Sitter spacetime. We consider a special gravitating, boson field configuration, a $q$-star, in 3, 4, 5 and 6 dimensions, within the framework of the above gravitational theory and find that the parameters of the stable stars are a few per cent different from the case of General Relativity.Comment: 18 pages, 14 figure

Domain walls on the surface of q-stars

We study domain-wall networks on the surface of q-stars in asymptotically flat or anti de Sitter spacetime. We provide numerical solutions for the whole phase space of the stable field configurations and find that the mass, radius and particle number of the star is larger but the scalar field, responsible for the formation of the soliton, acquires smaller values when a domain-wall network is entrapped on the star surface.Comment: 11 pages, 6 figures, to appear in Jurn. Math. Phy

Q-stars in scalar-tensor gravitational theories

We study q-stars in Brans-Dicke gravitational theory. We find that when the Brans-Dicke constant, $\omega_{\textrm{BD}}$, tends to infinity, the results of General Relativity are reproduced. For other values of $\omega_{\textrm{BD}}$, the particle number, mass and radius of the star and the absolute value of the matter field are a few percent larger than in the case of General Relativity. We also investigate the general scalar-tensor gravitational theory and find that the star parameters are a few percent larger than in the case of General Relativity.Comment: 14 pages, to appear in Phys. Lett.

Q-stars in 2+1 dimensions

We study q-stars with one or two scalar fields, non-abelian, and fermion-scalar q-stars in 2+1 dimensions in an anti de Sitter or flat spacetime. We fully investigate their properties, such as mass, particle number, radius, numerically, and focus on the matter of their stability against decay to free particles and gravitational collapse. We also provide analytical solutions in the case of flat spacetime and other special cases.Comment: 37 pg, to appear in Nucl. Phys.

Q-stars in extra dimensions

We study q-stars with global and local U(1) symmetry in extra dimensions in asymptotically anti de Sitter or flat spacetime. The behavior of the mass, radius and particle number of the star is quite different in 3 dimensions, but in 5, 6, 8 and 11 dimensions is similar to the behavior in 4.Comment: 18 pages, to appear in Phys. Rev.

EYM equations in the presence of q-stars

We study Einstein-Yang-Mills equations in the presence of gravitating non-topological soliton field configurations, of q-ball type. We produce numerical solutions, stable with respect to gravitational collapse and to fission into free particles, and we study the effect of the field strength and the eigen-frequency to the soliton parameters. We also investigate the formation of such soliton stars when the spacetime is asymptotically anti de Sitter.Comment: 11 pages, to appear in Phys. Rev.

Q-stars and charged q-stars

We present the formalism of q-stars with local or global U(1) symmetry. The equations we formulate are solved numerically and provide the main features of the soliton star. We study its behavior when the symmetry is local in contrast to the global case. A general result is that the soliton remains stable and does not decay into free particles and the electrostatic repulsion preserves it from gravitational collapse. We also investigate the case of a q-star with non-minimal energy-momentum tensor and find that the soliton is stable even in some cases of collapse when the coupling to gravity is absent.Comment: Latex, 19pg, 12 figures. Accepted in Phys. Rev.