Inflation for astronomers.

The concept of inflation was introduced into cosmology by Guth (48) about a decade ago. It has generated a remarkable degree of response, both positive and negative, from physicists. By hindsight, the idea appears a natural consequence of the concept of the phase transition, which is believed to have occurred in the very early epochs of the big bang universe, when the breakdown of the so-called grand unification symmetry took place. When it was first proposed, the concept was somewhat difficult to understand, however, as it combined ideas from particle physics with those from the general theory of relativity. Even today, controversy remains about important questions, e.g.: Was there really an inflationary phase in the Universe? If yes, what was the physical mechanism behind it? Given the mode of inflation, what tangible relics should that era have left for today? The authors present the basic idea in a form that is as free of the jargon of particle physics as possible, and focus attention on the last of the three questions posed above.