A seminal paper, dated 1981, marked the birth of what was to become the
most successful paradigm in modern cosmology following that of the big bang
itself: inflation. Its 25th birthday offered a welcome opportunity to celebrate
the phenomenological success of inflation and to gather the world leading scientists engaged in forefront research in this field. Such was the objective of
the XXII IAP colloquium, which took place at “Institut d’Astrophysique de
Paris” (IAP) in June 2006. During this meeting and the immediately following two-week workshop, scientists from the world over and from both observational and theoretical communities gathered to discuss the present status,
the achievements and the shortcomings as well as the future of the theory
of inflation. The numerous discussions that took place offered solid ground
for the publication of regular proceedings. However, inflationary cosmology
encompasses different disciplines of physics, from high energy physics to observational astrophysics, and it has also become a field of research in its own
right. Therefore it was felt that a more pedagogical text, containing exhaustive discussions of the ins and outs of inflation, would be more useful. This is
precisely what this present volume of the Lecture Notes in Physics series is
aiming at.
As is by now well known, cosmic inflation corresponds to an episode of
accelerated expansion in the very early Universe which solves the handful of
puzzles that plague the standard hot big bang cosmology, namely the flatness, horizon, monopole excess problems, and, in some models, the problem
of the primordial singularity. These achievements even come with a bonus: the
production of density perturbations to the level needed to explain the origin
of large scale structure of the Universe. The first chapter of this volume, by
A. Linde, introduces this framework, offers a historical overview of this subject
and develops the present status of the theory. This is followed L. Kofmann’s
discussion on preheating which describes how matter and radiation can have
been produced during this period which smoothly connects inflation with the
standard big bang phase.