Weakly Semialgebraic Spaces

The book is the second part of an intended three-volume treatise on semialgebraic topology over an arbitrary real closed field R. In the first volume (LNM 1173) the category LSA(R) or regular paracompact locally semialgebraic spaces over R was studied. Th

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1367

Manfred Knebusch

Weakly Semialgebraic Spaces

Springer-Verlag Berlin Heidelberg New York London Paris Tokyo

Lecture Notes in Mathematics Edited by A. Oold and B. Eckmann

1367

Manfred Knebusch

Weakly Semialgebraic Spaces

Springer-Verlag Berlin Heidelberg New York London Paris Tokyo

Author

Manfred Knebusch Fakultat fur Mathematik, Universitat Regensburg 8400 Regensburg, Federal Republic of Germany

Mathematics Subject Classification (1980): 14G30, 54E99, 54E60, 55005, 55N 10, 55N20, 55P05, 55P 10 ISBN 3-540-50815-5 Springer-Verlag Berlin Heidelberg New York ISBN 0-387-50815-5 Springer-Verlag New York Berlin Heidelberg

This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, re-use of illustrations. recitation. broadcasting, reproduction on microfilms or in other ways, and storage in data banks. Duplication of this publication or parts thereof is only permitted under the provisions of the German Copyright Law of September 9, 1965, in its version of June 24, 1985, and a copyright fee must always be paid. Violations fall under the prosecution act of the German Copyright Law.

© Springer-Verlag Berlin Heidelberg 1989 Printed in Germany Printing and binding: Druckhaus Beltz, Hemsbach/Bergstr. 2146/3140-543210

Introduction This is the second in a chain of (hopefully) three volumes devoted to an explication of the fundamentals of semialgebraic topology over an arbitrary real closed field R. We refer the uninitiated reader to the preface of the first volume [LSA)1 and some other papers cited there to get an idea of the program we have in mind with the term "semialgebraic topology" as a basis of real algebraic geometry.

Let us roughly recall what has been achieved in the first volume and where we stand now. As we explained in [LSA), the "good" locally semialgebraic spaces, which fortunately seem to suffice for most applications, are the regular paracompact ones. These are precisely those locally semialgebraic spaces which can be triangulated (I.4.8 and 11.4.4)2. Moreover, any locally finite family of locally semialgebraic sets in such a space can be triangulated simultaneously (II.4.4). This fact seems to be the key result for many proofs in [LSA).

We accomplished less work on the triangulation of locally semialgebraic maps. Here our main result has been the triangulability of finite maps (II.6.13). Much more can probably be done, as is to be expected by the book [V] of Verona, but we do not pursue this line of investigation in the present volume. {Verona works over

m

and uses transcendental

techniques.}

cf. the references

2

This refers to Example 4.8 in Chapter I and Theorem 4.4 in Chapter II of [LSA]. The main body of this volume starts with Chapter IV. The signs I, II, III refer to the chapters of [LSA].

IV

On the other hand we obtained in Chapter II of [LSA] a fairly detailed picture of the various possibilities how to "complete" a regular paracompact space M, i.e. to embed M densely