Reflection and Transmission at the Apparent Horizon during Gravitational Collapse

We examine the wave-functionals describing the collapse of a self-gravitating dust ball in an exact quantization of the gravity-dust system. We show that ingoing (collapsing) dust shell modes outside the apparent horizon must necessarily be accompanied by outgoing modes inside the apparent horizon, whose amplitude is suppressed by the square root of the Boltzmann factor at the Hawking temperature. Likewise, ingoing modes in the interior must be accompanied by outgoing modes in the exterior, again with an amplitude suppressed by the same factor. A suitable superposition of the two solutions is necessary to conserve the dust probability flux across the apparent horizon, thus each region contains both ingoing and outgoing dust modes. If one restricts oneself to considering only the modes outside the apparent horizon then one should think of the apparent horizon as a partial reflector, the probability for a shell to reflect being given by the Boltzmann factor at the Hawking temperature determined by the mass contained within it. However, if one considers the entire wave function, the outgoing wave in the exterior is seen to be the transmission through the horizon of the interior outgoing wave that accompanies the collapsing shells. This transmission could allow information from the interior to be transferred to the exterior.Comment: 19 pages, no figures. To appear in Phys. Rev.

The Quantum Stress-Tensor in Self-Similar Spherical Dust Collapse

We calculate the quantum stress tensor for a massless scalar field in the 2-d self-similar spherical dust collapse model which admits a naked singularity. We find that the outgoing radiation flux diverges on the Cauchy horizon. This may have two consequences. The resultant back reaction may prevent the naked singularity from forming, thus preserving cosmic censorship through quantum effects. The divergent flux may lead to an observable signature differentiating naked singularities from black holes in astrophysical observations.Comment: Latex File, 19 page

NEONATAL RESPIRATORY DISTRESS ... A CASE FOR OPHTHALMOLOGY?

Introdução: O dacriocistocelo congénito é uma obstrução rara do canal lacrimo-nasal no recém-nascido, que pode dar sintomatologia precoce. A fisiologia deve-se à obstrução proximal e distal do canal lacrimo-nasal. A apresentação clínica é variada e inclui formações quísticas, infetadas ou não, dificuldade na amamentação ou respiratória. A apresentação clássica é uma massa quística de coloração azulada, abaixo do epicanto interno. O diagnóstico correto implica exames complementares. A intervenção terapêutica está dependente da evolução clínica. O prognóstico é bom e geralmente não tem sequelas futuras. Caso clínico: As autoras apresentam o caso de um recém nascido, internado por dificuldade respiratória de início no segundo dia de vida. Ao exame objetivo tinha sinais de dificuldade respiratória e lesão circinada de aspeto semelhante a hematoma no canto interno do olho esquerdo. Nesta localização houve desenvolvimento posterior de formação quística com sinais inflamatórios, com diagnóstico inicial de dacriocistite. Após realização de tomografia computorizada das órbitas mostrou tratar-se de um dacriocistocelo. Conclusão: A dificuldade respiratória pode mesmo ser um caso oftalmológico

Innovation public policy—the case of Portugal

Innovation public policy has an essential role in influencing the competitive capacity of companies and is strongly asso-ciated with their ability to innovate and the way they are organized. As important as the technological organization of work is the social dimension, namely, involvement, participation, and commitment of the workforce, as these are, par excellence, factors that contribute to creating added value and differentiation for companies. In this sense, the concept of innovation depends on an integrated vision between the human dimension and the other multiple dimensions that innovation can assume. Public policies, besides the goal of creating a more modern and competitive business and industrial context, also are focused on the development of the workforce, not only in digital competences but also in soft skills. This type of skill contributes to creating a more innovative context and a culture of innovation. This article’s goal is to make a global overview of innovation and the public policies to promote the modernization of companies and influence the way they contribute to economic growth.info:eu-repo/semantics/publishedVersio

Estudo e implementação de modelo mais preciso para determinação da granulometria do solo por atenuação de raios gama.

bitstream/CNPDIA-2009-09/11030/1/BPD19_2007.pd

Entropy from the foam II

A simple model of spacetime foam, made by two different types of wormholes in a semiclassical approximation, is taken under examination: one type is a collection of $N_{w}$ Schwarzschild wormholes, while the other one is made by Schwarzschild-Anti-de Sitter wormholes. The area quantization related to the entropy via the Bekenstein-Hawking formula hints a possible selection between the two configurations. Application to the charged black hole are discussed.Comment: Revtex 3.0, 10 pages, Replaced version with minor changes and one ref. adde