ﻻ يوجد ملخص باللغة العربية
The aim of this paper is to study the stability of soliton-like static solutions via non-linear simulations in the context of a special class of massive tensor-multi-scalar-theories of gravity whose target space metric admits Killing field(s) with a periodic flow. We focused on the case with two scalar fields and maximally symmetric target space metric, as the simplest configuration where solitonic solutions can exist. In the limit of zero curvature of the target space $kappa = 0$ these solutions reduce to the standard boson stars, while for $kappa e 0$ significant deviations can be observed, both qualitative and quantitative. By evolving these solitonic solutions in time, we show that they are stable for low values of the central scalar field $psi_c$ while instability kicks in with the increase of $psi_c$. Specifically, in the stable region, the models oscillate with a characteristic frequency related to the fundamental mode. Such frequency tends to zero with the approach of the unstable models and eventually becomes imaginary when the solitonic solutions lose stability. As expected from the study of the equilibrium models, the change of stability occurs exactly at the maximum mass point, which was checked numerically with a very good accuracy.
Gravitational theories with multiple scalar fields coupled to the metric and each other --- a natural extension of the well studied single-scalar-tensor theories --- are interesting phenomenological frameworks to describe deviations from general rela
We compute the spectrum of scalar models with a general coupling to the scalar curvature. We find that the perturbative states of these theories are given by two massive spin-0 modes in addition to one massless spin-2 state. This latter mode can be i
We derive the odd parity perturbation equation in scalar-tensor theories with a non minimal kinetic coupling sector of the general Horndeski theory, where the kinetic term is coupled to the metric and the Einstein tensor. We derive the potential of t
This paper provides an extended exploration of the inverse-chirp gravitational-wave signals from stellar collapse in massive scalar-tensor gravity reported in [Phys. Rev. Lett. {bf 119}, 201103]. We systematically explore the parameter space that cha
In gravity theories that exhibit spontaneous scalarization, astrophysical objects are identical to their general relativistic counterpart until they reach a certain threshold in compactness or curvature. Beyond this threshold, they acquire a non-triv