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Linearized stability analysis of thin-shell wormholes with a cosmological constant
Spherically symmetric thin-shell wormholes in the presence of a cosmological constant are constructed applying the cut-and-paste technique implemented by Visser. Using the Darmois–Israel formalismExpand
Interior of a Schwarzschild Black Hole Revisited
Abstract The Schwarzschild solution has played a fundamental conceptual role in general relativity, and beyond, for instance, regarding event horizons, spacetime singularities and aspects of quantumExpand
Shear - free anisotropic cosmological models
A class of orthogonal, spatially homogeneous shear-free cosmological models with an imperfect liquid matter content is considered. It is shown that, for these models, the anisotropic stresses areExpand
Stability analysis of dynamic thin shells
We analyse the stability of generic spherically symmetric thin shells to linearized perturbations around static solutions. We include the momentum flux term in the conservation identity, deduced fromExpand
Generalized Observers and Velocity Measurements in General Relativity
To resolve some unphysical interpretations related to velocity measurements by static observers, we discuss the use of generalized observer sets, give a prescription for defining the speed of testExpand
Weak Energy Condition Violation and Superluminal Travel
Recent solutions to the Einstein Field Equations involving negative energy densities, i.e., matter violating the weak-energy-condition, have been obtained, namely traversable wormholes, theExpand
Time, Closed Timelike Curves and Causality
It seems to be extremely difficult to give a precise definition of Time, this mysterious ingredient of the Universe. Intuitively, we have the notion of time as something that flows. Ancient religionsExpand
Einstein in Portugal: Eddington's expedition to Principe and the reactions of Portuguese astronomers (1917–25)
Abstract Among various case studies addressing the reception of relativity, very few deal with Portugal at either the international or the national level. The national literature on the topic hasExpand
Dust-filled axially symmetric universes with a cosmological constant
Following the recent recognition of a positive value for the vacuum energy density and the realization that a simple Kantowski-Sachs model might fit the classical tests of cosmology, we study theExpand
How general is inflation in the presence of a non-minimal coupling?
Abstract The qualitative analysis of a Robertson-Walker geometry non-minimally coupled to a scalar field is summarized. It is claimed that a divergenceless effective energy-momentum tensor should beExpand