Topology and Measure

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133 Flemming Tops0e Department of Mathematics, University of Copenhagen

Topology and Measure

Springer-Verlag Berlin· Heidelberg· NewYork 1970

Lecture Notes in Mathematics A collection of informal reports and seminars Edited by A. Dold, Heidelberg and B. Eckmann, ZOrich

133 Flemming Tops0e Department of Mathematics, University of Copenhagen

Topology and Measure

Springer-Verlag Berlin· Heidelberg· NewYork 1970

This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically those of translation, reprinting, re-use of illustrations, broadcasting, reproduction by photocopying machine or similar means, and storage in data banks. Under § 54 of the German Copyright Law where copies are made for other than private use, a fee is payable to the publisher, the amount of the fee to be determined by agreement with the;publisher. by Springer-Verlag Berlin' Heidelberg 1970. Library of Congress Catalog Card Number 75-120379. Printed in Germany. Tide No. 3289.

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CONTENTS Preface introduction acknowledgments Preliminaries

IV IX

PART I 1. Measure and integral, definitions 2. Basic result on construction of a measure 3. Basic result on construction of an integral 4. Finitely additive theory 5. From "Baire" measures to "Borel" measures, an abstract approach 6. Construction of measures by approximation from outside and by approximation from inside 7. On the possibility of prOViding a space of measures with a vague topology

1 3 6 15 21

26 31

PART II 8. Definition and basic properties of the weak topology 9. Compactness in the weak topology 10. Criteria for weak convergence 11. On the structure of

40 42 45

12. 13. 14. 15. 16. 17.

51 54 60

A problem related to questions of uniformity First solution of the e-problem Second solution of the e-proolem Uniformity classes Joint continuity Preservation of weak convergence

47

64 66 68

Notes and remarks

72

References

78

PREFACE INTRODUCTION

Below we shall comment on the development which led to the results of the present volume (and of [26]). It will be seen that our investigations took their starting point in the theory of weak convergence of (probability-) measures, and that the results on measure and integration theory to be found in part I emerged as a kind of "by-product". During the inspiring lectures of professor P. Billingsley, I was for the first time presented to the theory of weak convergence. These lectures, which were based on the manuscript to the book

[3],

took

place in 1964-65 while professor Billingsley visited the institute of math. statistics at the university of Copenhagen. The contact with Billingsley resulted, among other things, in the joint paper

[4].

This paper was the

starting point of the development leading to the results obtained in sections 12-17. The academic year 1965-66 I spent at the statistical laboratory, the university of Cambridge, England. There I met professor K.R. Parthasarathy, who was at that time working on his book

dealing with weak

convergence too. Once