Riemann Surfaces, Theta Functions, and Abelian Automorphisms Groups

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483 Robert D. M. Accola

ETHICS ETH-HB *00100000135731*

II II U~IUII II II UlIII II MII III Riemann Surfaces, Theta Functions, and Abelian Automorphisms Groups m

Springer-Verlag

Berlin. Heidelberg. NewYork 1975

Author Prof. Robert D. M. Accola Department of Mathematics Brown University Providence, R.I. 02912 USA

Library of Congress Cataloging in Publication Data

Accola, Robert D M 1929Riemann sufaoes, theta functions, and abelian aut omorphism groups. (Lecture notes in mathematics ; 483) Bibliography: p. Includes index. i. Riemann surfaces. 2. Functions, Theta. 5. Aut omorphisms. 4. Abe lian groups. I. Title. II. Series: Lecture notes in mathematics (Berlin) ; 483. QA3.L28 no. 483 [QA333] 510'.8 [515'.223] 75-25928

AMS Subject Classifications (1970): 14 H40, 30A46 ISBN 3-540-07398-1 ISBN 0-387-07398-1

Springer-Verlag Berlin Heidelberg 9 New 9 York Springer-Verlag New York Heidelberg 9 Berlin 9

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 w 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. 9 by Springer-Verlag Berlin Heidelberg 9 1975 Printed in Germany Offsetdruck: Julius Beltz, Hemsbach/Bergstr.

Contents

Part I I Introduction

I

2 Remarks on general coverings

3 Resum~ of the Riemamnvamishlmg theorem RAmified normal coverings

7 8

5 Abeliancovers

12

6 Main ~esults

19

Part II i Introduction

32

2 Completely ramified abelian covers

@0

3 Two-sheeted covers

50

@ Other applications

56

5 Closing remarks

63

Part III i Introduction

66

2 Castelnuovo's method and P0-hyperellipticity

70

3 Extensions

7@

The p - 2 conjecture for p = 5

79

5 Elliptic-hyperelliptic surfaces of genus five

81

6 Elliptic-hyperelliptic surfaces of genus three

88

7 Cyclic groups of order three for genus two

9@

8 Some local characterizations

95

9 Closing remarks

98

References

100

Index

102

PA2~ X x)

i.

Introduction.

Torelli's

type of a Riemann surface

theorem states

is determined

class of) one of its period matrices. some property

If a Riemann surface has

by some property

a property which

period matrix at hand. characterizations problem,

by {the equivalence

not shared by all Riemann surfaces

should be characterized hopefully

that the conformal

then this fact

of the period matrix,

is independent

of the particular

The main tool for effecting

is Riemann's

solution

often called Riemann's

such

to the .~cobi inversion

vanishing

theorem.

Riemann's

theorem relates vanishing

properties

of the theta function

the. Jacobian of a surface

to certain

linear series on the surface.

Since special properties existence

of special

will be reflected, properties

on a Riemann

linear series,

via Riemann's

for