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INFORMATION to USERS This Manuscript Has Been Reproduced INFORMATION TO USERS This manuscript has been reproduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. 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Ann Arbor, Ml 48106-1346 USA 313/761-4700 800/521-0600 Order Number 9503152 Spectral geometry of hyperbolic 3-manifolds Callahan, Patrick James, Ph.D. University of Illinois at Urbana-Champaign, 1994 UMI 300N.ZeebRd Ann Arbor, MI 48106 SPECTRAL GEOMETRY OF HYPERBOLIC 3-MANIFOLDS BY PATRICK JAMES CALLAHAN B.A., University of California at San Diego, 1989 M.S., University of Illinois at Urbana-Champaign, 1990 THESIS Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Mathematics in the Graduate College of the University of Illinois at Urbana-Champaign, 1994 Urbana, Illinois UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN THE GRADUATE COLLEGE APRIL, 1994 WE HEREBY RECOMMEND THAT THE THESIS BY PATRICK JAMES CALLAHAN SPECTRAL GEOMETRY OF HYPERBOLIC 3-MANIFOLDS ENTITLED. BE ACCEPTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR DOCTOR OF PHILOSOPHY THE DEGREE OF_ Direct* 6f ThaSj* Research I LLslaA/1' (-/(In^iS? Head of Department Committee on Final Examination! t Required for doctor's degree but not for master's. ABSTRACT This thesis uses techniques from spectral geometry and builds from the work of Schoen, Culler and Shalen, Meyerhoff, and others to obtain various estimates and inequalities involving geometric data of hyperbolic 3-manifolds. These give numerical relationships between quantities like volume, length of geodesies, area of embedded surfaces, isoperimetric constants, eigenvalues of the Laplacian, and Margulis numbers for hyperbolic 3-manifolds. r DEDICATION This thesis is dedicated to my family, in particular my wife and daughter for all their help and support, my parents for their constant support and for raising me the way I would have raised myself, and my grandparents for i'neii accumulated wisdom and kindness. 1 thank them for making all things possible — concordia discors. iv ACKNOWLEDGEMENTS I would like to thank my advisor. Professor Wolfgang Haken, for being the exact type of advisor I needed, and for his support and confidence in me. I would also like to thank Professor Philippe Tondeur for all his geometric help and sage advice. I am also grateful to the committee members and all those who have listened and discussed things with me on my path to professional mathematics. Table of Contents Chapter 1. Introduction 1 Chapter 2. Lower bounds for the first eigenvalue and the isoperimetric constant 4 Chapter 3. Upper bounds for the first eigenvalue and the isoperimetric constant 18 Chapter 4. Applications of the bounds 23 Chapter 5. Some calculations of examples 28 References 32 Vita 34 vi Chapter 1 Introduction lopou nenXr\yiica Kcapiav nXt]yr]v eaco. Agamemnon, Aeschylus A quintessential mathematical problem is the classification of manifolds. This taxonomic nightmare has engaged topologists for the last hundred years. The classification of 2-manifolds was one of the great early triumphs of modern mathematics at the end of the 19th century. In the beginning of the 20th century it was not clear how one would deal with manifolds of dimension three, let alone higher dimensions. As it turned out, the high dimensional manifolds (dimensions five and higher) were handled by the 1960s. We should at this point say something about classification. In two dimensions, closed oriented manifolds are determined up to homeomorphism by the Euler characteristic. This invariant is easy to compute and can be calculated using a wide variety of techniques, from homological methods to the Gauss-Bonnet theorem. This is a very satisfactory classification in that it gives a complete description of all the possible 2-manifolds and a practical way of identifying them. It is known that such a classification cannot exist for manifolds of dimension four or more. In high dimensions this deficiency has been made up for by powerful techniques like surgery and the h-cobordism theorem which can be used to understand and work with the structure of high dimensional manifolds. Another difference between low dimensions and high dimensions is the distinctness of the categories of topological, piecewise linear, and smooth manifolds. In dimensions five and higher these three categories are all distinct. Furthermore a topological manifold can possess inequivalenl PL structures, and a PL manifold can possess inequivalent smooth structures. 1 In dimension four there has been much current research activity. Topologically, 4- manifolds are similar to high dimensional manifolds, namely surgery and cobordism theorems hold as they do in high dimensions. As for smooth 4-manifolds (every PL 4- manifold has a unique smoothing) matters are completely different. For one, the smooth versions of the surgery theorems from high dimensions fail in four dimensions. For another, there are compact closed 4-manifolds which possess an infinite number of distinct smooth structures. Additionally, there are exotic R s, i.e. manifolds homeomorphic to the standard Euclidean four-space but not diffeomorphic to it. Thus, 4-dimensional manifolds are quite different than manifolds in any other dimension. In dimensions two and three every topological manifold has a unique smooth structure. This allows for an exciting interplay between the topology and the geometry of the manifolds. For example, the uniformization of Riemann surfaces can be thought of as a geometric classification of topological 2-manifolds. This is an important viewpoint because it can be generalized to three dimensions. Thurston has formulated a Geometrization Conjecture which states that every 3-manifold can be canonically decomposed into geometric pieces. These geometric pieces are all of the form XjT where X is one of eight model geometric spaces and T is a discrete subgroup of the group of isometries of X. Of these eight model geometries, seven have been classified in the sense that there is a list of all possible types of manifolds and a practical set of invariants for identifying them. Six of these geometries correspond to the Seifert fibered spaces which were classified by Seiferi in the 1930's. The one. geometry which remains somewhat intractable is hyperbolic geometry. Hyperbolic manifolds are those manifolds which admit a Riemannian metric of constant curvature of -1. In the 1960's it was proved that every closed oriented 3-manifold was obtained by surgery on a link in the 3-sphere. In the early 1980's it was proved that on most links almost every surgery yields a hyperbolic 3-manifold. Thus, in some sense most 3- manifolds admit hyperbolic structures. Additionally, by the Mostow Rigidity theorem, a 2 hyperbolic manifold has a unique hyperbolic structure, thus the topology uniquely determines the geometry. In this thesis we will investigate the geometry of hyperbolic 3- manifolds. In particular we would like to understand the "shape" of hyperbolic 3- inanifolds. There are many numerical quantities associated with a Riemannian manifold which describe the shape of the manifold. For hyperbolic 3-manifolds, these quantities all become topological invariants. Several geometric invariants have already been studied in some detail like volume and the Chern-Simons invariant. In this thesis we will look more closely at two other numbers: the first eigenvalue and the isoperimetric constant. These two quantities are closely related and tend to occur in the realm of spectral geometry, hence the title of this thesis. In the next chapter we will consider lower bounds for the first eigenvalue and the isoperimetric constant. In the third chapter we will look at upper bounds. These bounds will take the form of inequalities depending on geometric quantities like volume, diameter, and injectivity radius. In the fourth chapter we will apply these results by combining the various bounds. In the last chapter we will look at a few explicit examples of hyperbolic 3- manifolds and their numerical invariants. 3 Chapter 2 Lower bounds for the first eigenvalue and the isoperimetric constant Introduction. There is an extensive body of literature concerning the study of low eigenvalues of Riemannian manifolds of negative curvature. Most of these works emphasize the case of Riemann surfaces. One of the reasons for this has been the paucity of examples and constructions of higher dimensional manifolds. In recent years this lacuna has been filled, at least in dimension three, by the work of Thurston, Jorgensen, Riley, and others. Now that we have an abundance of examples to work with, we hope to emulate that great work which has been done for surfaces and establish a better understanding of the relationship between the spectral data of a hyperbolic three-manifold and its geometry and topology.
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