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In the context of gauge/gravity dualities, we calculate the scalar and tensor mass spectrum of the boundary theory defined by a special 8-scalar sigma-model in five dimensions, the background solutions of which include the 1-parameter…
We construct spherically symmetric boson star solutions in $D \in \{4,5,6\}$ spacetime dimensions, considering the effects of both a quartic self-interaction term and a solitonic potential. We then perform a perturbative analysis,…
In the investigation and resolution of the cosmological constant problem the inclusion of the dynamics of quantum gravity can be a crucial step. In this work we suggest that the quantum constraints in a canonical theory of gravity can…
We consider the problem of building inhomogeneous cosmological models in scalar-tensor theories of gravity. This starts by splitting the field equations of these theories into constraint and evolution equations, and then proceeds by…
The existence of localized, approximately stationary, lumps of the classical gravitational and electromagnetic field -- $geons$ -- was conjectured more than half a century ago. If one insists on exact stationarity, topologically trivial…
This research paper investigates the impact of non-metricity and matter source on the geometry of charged spheres in the presence of anisotropic matter configuration. We use a specific model of extended symmetric teleparallel theory to…
Exact static, spherically symmetric solutions to the Einstein-Abelian gauge-dilaton equations, in $D$-dimensional gravity with a chain of $n$ Ricci-flat internal spaces are considered, with the gauge field potential having three nonzero…
A self-interacting SU(2)-doublet of complex scalar fields, minimally coupled to Einstein-Gauss-Bonnet gravity is considered in five space-time dimensions. The classical equations admit two families of solitons corresponding to spinning and…
In this work we present some new results which we have obtained in a study of the phase diagram of charged compact boson stars in the theory involving massive complex scalar fields coupled to the U(1) gauge field and gravity in a conical…
We discuss self-consistent geometries and behavior of dilaton in exactly solvable models of 2D dilaton gravity, with quantum fields in the Boulware state. If the coupling $H(\phi)$ between curvature and dilaton $\phi $ is non-monotonic,…
A general homogeneous two dimensional dilaton gravity model considered recently by Lemos and S\` a, is given quantum matter Polyakov corrections and is solved numerically for several static, equilibrium scenarii. Classically the dilaton…
In this paper, we developed three analytical models and obtained a new class of solutions describing compact stellar structures using the theory of teleparallel gravity. We consider the general anisotropic nature of stellar configurations…
We investigate cosmological evolutions of the bulk scalar field $\phi(t)$ and the radion $d(t)$ in five-dimensional dilatonic two branes model. The bulk potential for the scalar field is taken as the exponential function $V_{bulk} \propto…
This paper delves into the impact of extended symmetric teleparallel theory on anisotropic compact stellar structures. The explicit field equations were formulated by considering a minimum model of this extended gravity. Basically, the…
In this thesis special emphasis is put on the quantization of the spherically reduced Einstein-massless-Klein-Gordon model using a first order approach for geometric quantities, because phenomenologically it is probably the most relevant of…
We study the axial (or odd-parity) perturbations of neutron stars in a one-parameter subclass of Degenerate Higher-Order Scalar-tensor (DHOST) theories. After recalling the equilibrium neutron star configurations obtained in a previous work…
Rotating deformed neutron stars are important potential sources for groundbased gravitational-wave interferometers such as LIGO, GE0600 and VIRGO. One mechanism that may lead to significant non-asymmetries is the internal magnetic field. It…
We study exact, analytic, static, spherically symmetric, four-dimensional solutions of minimally coupled Einstein-scalar gravity, sourced by a scalar field whose profile has the form of the sine-Gordon soliton. We present a horizonless,…
We introduce a new type of generating theorems in General Relativity for anisotropic, static, spherically symmetric solutions of the Einstein field equations. The results are used to derive a class of solutions that can serve as new models…
Scalar boson stars and Dirac stars are solitonic solutions of the Einstein{Klein-Gordon and Einstein- Dirac classical equations, respectively. Despite the different bosonic vs: fermionic nature of the matter field, these solutions to the…