How much negative energy does a wormhole need?

It is known that traversible wormholes require negative energy density. We here argue how much negative energy is needed for wormholes, using a local analysis which does not assume any symmetry. and in particular allows dynamic (non-stationary) but non-degenerate wormholes. We find that wormholes require two constraints on the energy density, given by two independent components of the Einstein equation.Comment: 6 pages, no figure

Gravitational waves from quasi-spherical black holes

A quasi-spherical approximation scheme, intended to apply to coalescing black holes, allows the waveforms of gravitational radiation to be computed by integrating ordinary differential equations.Comment: 4 revtex pages, 2 eps figure

Numerical Solutions of Dilaton Gravity and the Semi-Classical Singularity

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 field ranges the whole real line, whereas in the semi-classical theory, with the usual definition, it is always below a certain critical value at which a singularity appears. We give solutions for both sub- and super-critical dilaton field. The pasting together of the spacetime on both sides of a singularity in semi-classical planar general relativity is discussed.Comment: 23 pages, LateX, 12 figures uuencode

The economics of Rayon

Thesis (M.B.A.)--Boston Universit

In search of a third place: a telecollaborative model for languaculture learning

This thesis presents a five-year, global classroom project, in which French and American students study the same texts (literature, film remakes, works of sociology and anthropology), while corresponding using ICTs. Their reflections provide the basis for the development of conceptual and perceptual toolkits, containing consciousness-raising activities on individual and culturally-biased semantic and perceptual differences and similarities. Students compare home culture images and the corresponding images from the other culture(s), in an attempt to arrive at a "third place" (Kramsch 1993), as an intercultural speaker (Byraml995; 1997). Feedback and transcripts from participants are used to assess the effectiveness of this pedagogy of languaculture in broadening discourse options and educational opportunities, and of the role of telecollaboration in student motivation and engagement. The analytical framework draws on insights of Bakhtin, Vygotsky and Flarre and Gillet, focussing on the learner as agent, and language as fundamentally dialogic in nature. Telecollaboration provides access to multiple discursive perspectives and negotiation of meaning, whereby students, especially the more motivated, ask real questions and receive real answers. The global classroom leads to a change in the locus of control, increasing motivation and encouraging students to appropriate their own learning. Significant individual, group and cross-cultural differences emerge in the interpretation and degree of appropriation of the materials and opportunities for intercultural communication. This thesis provides research-informed, pedagogical guidelines for developing similar intercultural telecollaborative courses and makes a creative contribution, both to the dialogic teaching of language as culture and to the integration of new technologies into the curriculum