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Linearized stability analysis of thin-shell wormholes with a cosmological constant

- Francisco S. N. Lobo, P. Crawford
- Physics
- 1 November 2003

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 formalism… Expand

Interior of a Schwarzschild Black Hole Revisited

- R. Doran, Francisco S. N. Lobo, P. Crawford
- Physics
- 12 September 2006

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 quantum… Expand

Shear - free anisotropic cosmological models

- J. P. Mimoso, P. Crawford
- Physics
- 1 February 1993

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 are… Expand

Stability analysis of dynamic thin shells

- Francisco S. N. Lobo, P. Crawford
- Physics
- 14 July 2005

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 from… Expand

Generalized Observers and Velocity Measurements in General Relativity

- P. Crawford, I. Tereno
- Physics
- 21 November 2001

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 test… Expand

Weak Energy Condition Violation and Superluminal Travel

- Francisco S. N. Lobo, P. Crawford
- Physics
- 9 April 2002

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, the… Expand

Time, Closed Timelike Curves and Causality

- Francisco S. N. Lobo, P. Crawford
- Physics, Mathematics
- 26 June 2002

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 religions… Expand

Einstein in Portugal: Eddington's expedition to Principe and the reactions of Portuguese astronomers (1917–25)

- Elsa Mota, P. Crawford, A. Simões
- Sociology
- The British Journal for the History of Science
- 22 December 2008

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 has… Expand

Dust-filled axially symmetric universes with a cosmological constant

- P. Aguiar, P. Crawford
- Physics
- 15 September 2000

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 the… Expand

How general is inflation in the presence of a non-minimal coupling?

- A. Barroso, J. Casasayas, P. Crawford, P. Moniz, A. Nunes
- Physics
- 30 January 1992

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 be… Expand

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