Assuntos
Antígenos de Protozoários/imunologia , Comportamento Animal/efeitos dos fármacos , DNA de Protozoário/sangue , Imunização , Toxoplasma/química , Animais , Animais Recém-Nascidos , Antígenos de Protozoários/administração & dosagem , Contagem de Células Sanguíneas , Comportamento Exploratório/efeitos dos fármacos , Linfonodos/efeitos dos fármacos , Linfonodos/imunologia , Linfonodos/patologia , Aprendizagem em Labirinto/efeitos dos fármacos , Ratos , Baço/efeitos dos fármacos , Baço/imunologia , Baço/patologia , Timo/efeitos dos fármacos , Timo/imunologia , Timo/patologia , Toxoplasma/imunologiaRESUMO
The Cosmic Microwave Background provides our most ancient image of the universe and our best tool for studying its early evolution. Theories of high-energy physics predict the formation of various types of topological defects in the very early universe, including cosmic texture, which would generate hot and cold spots in the Cosmic Microwave Background. We show through a Bayesian statistical analysis that the most prominent 5 degrees -radius cold spot observed in all-sky images, which is otherwise hard to explain, is compatible with having being caused by a texture. From this model, we constrain the fundamental symmetry-breaking energy scale to be (0) approximately 8.7 x 10(15) gigaelectron volts. If confirmed, this detection of a cosmic defect will probe physics at energies exceeding any conceivable terrestrial experiment.
RESUMO
The role of cosmic microwave background polarization data in constraining the presence of primordial isocurvature modes is examined. While MAP will be unable to simultaneously constrain isocurvature modes and cosmological parameters, PLANCK will set strong limits on isocurvature modes. If one allows isocurvature modes, the recently obtained BOOMERANG measurement of the curvature of the Universe fails. However, a comparably sensitive polarization measurement on the same angular scales will permit a determination of the curvature without the prior assumption of adiabaticity.
RESUMO
The question of whether there was a Beginning of the Universe is a truly challenging puzzle for physics and for philosophy. Classical general relativity implies that our observable universe originated in a singularity fifteen billion years ago, but this may be merely a reflection of the incompleteness of the theory. Inflationary theory and quantum cosmology provide our best current attempt to describe these early moments. It has been claimed that the inflationary mechanism renders moot the question of exactly how the universe began. I argue that, on the contrary, if one asks the question of what was in the past, we find ourselves staring directly back at a putative Beginning after all.
