Mixed configurations of tensor-multiscalar solitons and neutron stars

Abstract

In the present paper we consider special classes of massive tensor-multi-scalar theories of gravity whose target space metric admits Killing field(s) with a periodic flow. For such tensor-multi-scalar theories we show that there exist mixed configurations of tenor-multiscalar solitons and relativistic (neutron) stars. The influence of the curvature of the target space on the structure of the mixed configurations is studied for two explicit scalar-tensor theories. The stability of the obtained compact objects is examined and it turns out that the stability region spans to larger central energy densities and central values of the scalar field compared to the pure neutron stars or the pure tensor-multi-scalar solitons. * Electronic address: daniela.doneva@uni-tuebingen.de † Electronic address: yazad@phys.uni-sofia.bg arXiv:1909.00473v1 [gr-qc] 1 Sep 2019

Rotating tensor-multiscalar solitons

“…The focus of the present paper falls exactly in this area dealing with the less explored case of multiple scalar fields [3,4]. Such tensor-multi-scalar theories are on one hand complicated and difficult to handle, but on the other hand they posses a lot of freedom and possibilities to construct new and very interesting solutions [5][6][7]. In addition, they are in agreement with the observations and do not have severe intrinsic mathematical problems.…”

“…In the simplest case when this target space metric is the flat one, the field equations describing the solutions coincide with the corresponding ones for boson stars, but the phenomenology can be much richer for other non-flat target space metrics. In addition, in these theories mixed configurations of solitons and neutron stars exist [6]. A natural next step is to generalize the solutions in [5] to the case of rapid rotation that is the focus of the present paper.…”

Dark compact objects in massive tensor-multi-scalar theories of gravity

“…where m is the mass of the scalar fields and λ (4) is parameter governing the ψ 4 -self-interaction of the scalar fields. This Einstein frame potential is natural from physical point of view and in addition it is universal for all tensor-multi-scalar theories, i.e.…”

“…For some particular theories and under additional requirements a rough estimate of the soliton mass M is possible. Such a theory is (15) with β < 0 and λ (4) = κ = 0. In this particular case, provided that the neutron stars are scalarized, a rough constraint on the mass m can be obtained as in [5,6], namely 10 −16 eV < m < 10 −9 eV.…”

“…This description is specific for N = 2 and there is no natural extensions to higher dimensions with N ≥ 3 in the general case. When we consider the presence of matter the description/interpretation in terms of one (or more) complex scalar field(s) only is either impossible or rather problematic in the general case with N ≥ 3 [4]. That is why we prefer to use here the general geometrical description/construction instead of introducing an effective exotic complex field.…”