München 1997 – scientific programme

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PV: Plenarvorträge

PV XI

PV XI: Plenary Talk

Thursday, March 20, 1997, 08:30–09:30, Aula

Is there a Need for New Physics in Cosmology? — •Nathalie Deruelle — DARC, Observatoire de Paris, F-92190 Meudon, France

The origin of galaxies, clusters etc is one of the most puzzling questions in cosmology.

Presently two families of models can produce initial density fluctuations which eventually grow by gravitational instability to form the observed structures: Inflationary and topological defect scenarios. Both rely on speculations about the properties of matter at very high (≃ 10¹⁶ GeV) energies.

In the inflationary scenario, the expansion of the universe was driven, at a very early stage of its history, by a scalar field, the quantum fluctuations of which were dramatically amplified when that stage ended. The topological defect scenario, on the other hand, is based on the idea that a number of phase transitions took place as the universe cooled down. Topological defects could then have appeared and played the role of seeds for structure formation.

In this talk I shall try to explain why such new physics was introduced and how observations of the cosmic microwave background can test the predictions.