Related papers: The Negative Energy in Generalized Vaidya Spacetim…
In this dissertation we study two well known gravitational scenarios in which singularities may appear; the final state of gravitational collapse and the late time evolution of the universe. In the first scenario, we study a spherically…
In this paper, we will analyze a time dependent geometry in a massive theory of gravity. This will be done by analyzing Vaidya space-time in such a massive theory of gravity. As gravitational collapse is a time dependent system, we will…
In this work, we explore the properties of timelike geodesic for particles with zero energy. We found some similarities between geodesic motion in Schwarzschild black hole and timelike geodesics for particles with zero energy. We show, that…
This study examines the gravitational collapse of an overdense dark matter region in a coupled scalar field dark energy scenario within a flat FLRW background. It finds that, depending on the initial conditions, some overdense regions avoid…
The theoretical and phenomenological status of negative energies is reviewed in Quantum Field theory leading to the conclusion that hopefully their rehabilitation might only be completed in a modified general relativistic model
We investigate the occurrence and nature of naked singularities in the gravitational collapse of an adiabatic perfect fluid in self-similar higher dimensional space-times. It is shown that strong curvature naked singularities could occur if…
The exterior of a relativistic star can be modelated with the Vaidya radiating metric. It is started from the generalized Vaidya metric that allows a type II fluid and studied the conditions of generating new analytical solutions of the…
In this paper we extend the analysis of gravitational collapse of generalised Vaidya spacetimes to higher dimensions, in the context of the Cosmic Censorship Conjecture. We present the sufficient conditions on the generalised Vaidya mass…
We extend Vaidya's algorithm for the description of a central mass losing or gaining energy due to electromagnetic-type radiation (`null dust') to the case of arbitrary radial corpuscular radiation. We also demonstrate the remarkable…
In this work we study collapse of a general matter in a most general spacetime i.e., a spacetime with any matter and without (assuming) any symmetry. We show that the energy is completely trapped inside the null singularity and therefore…
An outstanding problem in gravitation theory and relativistic astrophysics today is to understand the final outcome of an endless gravitational collapse. Such a continual collapse would take place when stars more massive than few times the…
In this paper, the different properties of generalized Vaidya spacetime are considered. We define the location of horizons. We show that the apparent horizon can contain the event horizon. The locations of all types of horizons are compared…
We discuss the weight of vacuum energy in various contexts. First, we compute the vacuum energy for flat spacetimes of the form $\mathbb{T}^3 \times \mathbb{R}$, where $\mathbb{T}^3$ stands for a general 3-torus. We discover a quite simple…
We consider a static, axially symmetric, and asymptotically flat exact solution of the Einstein vacuum equations, known as the gamma metric. This is characterized by two constant parameters $m$ and $\gamma$. We find that the total energy…
We provide a covariant derivation of plasma physics coupled to gravitation by utilizing the 3+1 formulation of general relativity, including a discussion of the Lorentz force law. We then reduce the system to the spherically symmetric case…
In the expansive nondecelerative universe model, creation of matter occurs due to which the Vaidya metrics is applied. This fact allows for localizing gravitational energy and calculating the energy of gravitational waves using an approach…
We study singularities which can form in a spherically symmetric gravitational collapse of a general matter field obeying weak energy condition. We show that no energy can reach an outside observer from a null naked singularity. That means…
In general relativity, the endpoint of spherically symmetric gravitational collapse is a Schwarzschild--[(A)dS] black hole. In bimetric gravity, it has been speculated that a static end state must also be Schwarzschild--[(A)dS]. To this…
In this article, we present a gravitational collapse null dust solution of the Einstein field equations. The spacetime is regular everywhere except on the symmetry axis where it possesses a naked curvature singularity, and admits one…
The existence of spacetime singularities is one of the biggest problems of nowadays physics. According to Penrose, each physical singularity should be covered by a "cosmic censor" which prevents any external observer from perceiving their…