This volume collects six related articles. The first is the notes (written by J.S. Milne) of a major part of the seminar "Periodes des Int grales Abeliennes" given by P. Deligne at I'.B.E.S., 1978-79. The second article was written for this volume (by P. Deligne and J.S. Milne) and is largely based on: N Saavedra Rivano, Categories tannakiennes, Lecture Notes in Math. 265, Springer, Heidelberg 1972. The third article is a slight expansion of part of: J.S. Milne and Kuang-yen Shih, Sh ura varieties: conjugates and the action of complex conjugation 154 pp. (Unpublished manuscript, October 1979). The fourth article is based on a letter from P. De1igne to R. Langlands, dated 10th April, 1979, and was revised and completed (by De1igne) in July, 1981. The fifth article is a slight revision of another section of the manuscript of Milne and Shih referred to above. The sixth article, by A. Ogus, dates from July, 1980.

ltats - avec une generalite minimale, souvent insuffisante pour les applications -et une idee de leur demonstration. Pour des resultats complets, ou des demonstrationsdetaillees, SGA 4 reste indispensable.Le "Rapport sur la formule des traces" contient une demonstration complete dela formule des traces pour l'endomorphisme de Frobenius. La demonstration est celledonnee par Grothendieck dans SGA 5, elaguee de tout detail inutile. Ce rapportdevrait permettre a utilisateur d'oublier SGA 5, qu'on pourra considerer comme uneserie de digression, certaines tres interessantes. Son existence permettra de publierprochainement SGA 5 tel quel. Il est complete par l'expose "Applications de laformule des traces aux sommes trigonometriques" qui explique comment la formuledes traces permet l'etude de sommes trigonometriques, et donne des exemples..

The first part of this monograph is devoted to a characterization of hypergeometric-like functions, that is, "twists" of hypergeometric functions in "n"-variables. These are treated as an ("n"+1) dimensional vector space of multivalued locally holomorphic functions defined on the space of "n"+3 tuples of distinct points on the projective line "P" modulo, the diagonal section of Auto "P"="m." For "n"=1, the characterization may be regarded as a generalization of Riemann's classical theorem characterizing hypergeometric functions by their exponents at three singular points.

This characterization permits the authors to compare monodromy groups corresponding to different parameters and to prove commensurability modulo inner automorphisms of "PU"(1, "n").

The book includes an investigation of elliptic and parabolic monodromy groups, as well as hyperbolic monodromy groups. The former play a role in the proof that a surprising number of lattices in "PU"(1,2) constructed as the fundamental groups of compact complex surfaces with constant holomorphic curvature are in fact conjugate to projective monodromy groups of hypergeometric functions. The characterization of hypergeometric-like functions by their exponents at the divisors "at infinity" permits one to prove generalizations in "n"-variables of the Kummer identities for "n"-1 involving quadratic and cubic changes of the variable.

Ideas from quantum field theory and string theory have had considerable impact on mathematics over the past 20 years. Advances in many different areas have been inspired by insights from physics. In 1996-97 the Institute for Advanced Study (Princeton, New Jersey) organized a special year-long programme designed to teach mathematicians the basic physical ideas which underlie the mathematical applications. The purpose was to create and convey an understanding, in terms useful to mathematicians, of some fundamental notions of physics and develop the sort of intuition common among physicists for those who are used to thought processes stemming from geometry and algebra. These volumes are a written record of the programme. They contain notes from several long and many short courses covering various aspects of quantum field theory and perturbative string theory. The courses were given by leading physicists and the notes were written either by the speakers or by mathematicians who participated in the programme. The book also includes problems and solutions worked out by the editors and participants. Interspersed are mathematical texts with background material and commentary on some topics