Milnor, John W. Groups of Homotopy Spheres
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Commentary on the Kervaire–Milnor Correspondence 1958–1961
BULLETIN (New Series) OF THE AMERICAN MATHEMATICAL SOCIETY Volume 52, Number 4, October 2015, Pages 603–609 http://dx.doi.org/10.1090/bull/1508 Article electronically published on July 1, 2015 COMMENTARY ON THE KERVAIRE–MILNOR CORRESPONDENCE 1958–1961 ANDREW RANICKI AND CLAUDE WEBER Abstract. The extant letters exchanged between Kervaire and Milnor during their collaboration from 1958–1961 concerned their work on the classification of exotic spheres, culminating in their 1963 Annals of Mathematics paper. Michel Kervaire died in 2007; for an account of his life, see the obituary by Shalom Eliahou, Pierre de la Harpe, Jean-Claude Hausmann, and Claude We- ber in the September 2008 issue of the Notices of the American Mathematical Society. The letters were made public at the 2009 Kervaire Memorial Confer- ence in Geneva. Their publication in this issue of the Bulletin of the American Mathematical Society is preceded by our commentary on these letters, provid- ing some historical background. Letter 1. From Milnor, 22 August 1958 Kervaire and Milnor both attended the International Congress of Mathemati- cians held in Edinburgh, 14–21 August 1958. Milnor gave an invited half-hour talk on Bernoulli numbers, homotopy groups, and a theorem of Rohlin,andKer- vaire gave a talk in the short communications section on Non-parallelizability of the n-sphere for n>7 (see [2]). In this letter written immediately after the Congress, Milnor invites Kervaire to join him in writing up the lecture he gave at the Con- gress. The joint paper appeared in the Proceedings of the ICM as [10]. Milnor’s name is listed first (contrary to the tradition in mathematics) since it was he who was invited to deliver a talk. -
On the Stable Classification of Certain 4-Manifolds
BULL. AUSTRAL. MATH. SOC. 57N65, 57R67, 57Q10, 57Q20 VOL. 52 (1995) [385-398] ON THE STABLE CLASSIFICATION OF CERTAIN 4-MANIFOLDS ALBERTO CAVICCHIOLI, FRIEDRICH HEGENBARTH AND DUSAN REPOVS We study the s-cobordism type of closed orientable (smooth or PL) 4—manifolds with free or surface fundamental groups. We prove stable classification theorems for these classes of manifolds by using surgery theory. 1. INTRODUCTION In this paper we shall study closed connected (smooth or PL) 4—manifolds with special fundamental groups as free products or surface groups. For convenience, all manifolds considered will be assumed to be orientable although our results work also in the general case, provided the first Stiefel-Whitney classes coincide. The starting point for classifying manifolds is the determination of their homotopy type. For 4- manifolds having finite fundamental groups with periodic homology of period four, this was done in [12] (see also [1] and [2]). The case of a cyclic fundamental group of prime order was first treated in [23]. The homotopy type of 4-manifolds with free or surface fundamental groups was completely classified in [6] and [7] respectively. In particular, closed 4-manifolds M with a free fundamental group IIi(M) = *PZ (free product of p factors Z ) are classified, up to homotopy, by the isomorphism class of their intersection pairings AM : B2{M\K) x H2(M;A) —> A over the integral group ring A = Z[IIi(M)]. For Ui(M) = Z, we observe that the arguments developed in [11] classify these 4-manifolds, up to TOP homeomorphism, in terms of their intersection forms over Z. -
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ISOPARAMETRIC FUNCTIONS ON EXOTIC SPHERES CHAO QIAN AND ZIZHOU TANG Abstract. This paper extends widely the work in [GT13]. Existence and non-existence results of isoparametric functions on exotic spheres and Eells-Kuiper projective planes are established. In particular, every homotopy n-sphere (n > 4) carries an isoparametric function (with certain metric) with 2 points as the focal set, in strong contrast to the classification of cohomogeneity one actions on homotopy spheres [St96] ( only exotic Kervaire spheres admit cohomogeneity one actions besides the standard spheres ). As an application, we improve a beautiful result of B´erard-Bergery [BB77] ( see also pp.234-235 of [Be78] ). 1. Introduction Let N be a connected complete Riemannian manifold. A non-constant smooth function f on N is called transnormal, if there exists a smooth function b : R R such that f 2 = → |∇ | b( f ), where f is the gradient of f . If in addition, there exists a continuous function a : ∇ R R so that f = a( f ), where f is the Laplacian of f , then f is called isoparametric. → △ △ Each regular level hypersurface is called an isoparametric hypersurface and the singular level set is called the focal set. The two equations of the function f mean that the regular level hypersurfaces of f are parallel and have constant mean curvatures, which may be regarded as a geometric generalization of cohomogeneity one actions in the theory of transformation groups ( ref. [GT13] ). Owing to E. Cartan and H. F. M¨unzner [M¨u80], the classification of isoparametric hy- persurfaces in a unit sphere has been one of the most challenging problems in submanifold geometry. -
The Kervaire Invariant in Homotopy Theory
The Kervaire invariant in homotopy theory Mark Mahowald and Paul Goerss∗ June 20, 2011 Abstract In this note we discuss how the first author came upon the Kervaire invariant question while analyzing the image of the J-homomorphism in the EHP sequence. One of the central projects of algebraic topology is to calculate the homotopy classes of maps between two finite CW complexes. Even in the case of spheres – the smallest non-trivial CW complexes – this project has a long and rich history. Let Sn denote the n-sphere. If k < n, then all continuous maps Sk → Sn are null-homotopic, and if k = n, the homotopy class of a map Sn → Sn is detected by its degree. Even these basic facts require relatively deep results: if k = n = 1, we need covering space theory, and if n > 1, we need the Hurewicz theorem, which says that the first non-trivial homotopy group of a simply-connected space is isomorphic to the first non-vanishing homology group of positive degree. The classical proof of the Hurewicz theorem as found in, for example, [28] is quite delicate; more conceptual proofs use the Serre spectral sequence. n Let us write πiS for the ith homotopy group of the n-sphere; we may also n write πk+nS to emphasize that the complexity of the problem grows with k. n n ∼ Thus we have πn+kS = 0 if k < 0 and πnS = Z. Given the Hurewicz theorem and knowledge of the homology of Eilenberg-MacLane spaces it is relatively simple to compute that 0, n = 1; n ∼ πn+1S = Z, n = 2; Z/2Z, n ≥ 3. -
EXOTIC SPHERES and CURVATURE 1. Introduction Exotic
BULLETIN (New Series) OF THE AMERICAN MATHEMATICAL SOCIETY Volume 45, Number 4, October 2008, Pages 595–616 S 0273-0979(08)01213-5 Article electronically published on July 1, 2008 EXOTIC SPHERES AND CURVATURE M. JOACHIM AND D. J. WRAITH Abstract. Since their discovery by Milnor in 1956, exotic spheres have pro- vided a fascinating object of study for geometers. In this article we survey what is known about the curvature of exotic spheres. 1. Introduction Exotic spheres are manifolds which are homeomorphic but not diffeomorphic to a standard sphere. In this introduction our aims are twofold: First, to give a brief account of the discovery of exotic spheres and to make some general remarks about the structure of these objects as smooth manifolds. Second, to outline the basics of curvature for Riemannian manifolds which we will need later on. In subsequent sections, we will explore the interaction between topology and geometry for exotic spheres. We will use the term differentiable to mean differentiable of class C∞,and all diffeomorphisms will be assumed to be smooth. As every graduate student knows, a smooth manifold is a topological manifold that is equipped with a smooth (differentiable) structure, that is, a smooth maximal atlas. Recall that an atlas is a collection of charts (homeomorphisms from open neighbourhoods in the manifold onto open subsets of some Euclidean space), the domains of which cover the manifold. Where the chart domains overlap, we impose a smooth compatibility condition for the charts [doC, chapter 0] if we wish our manifold to be smooth. Such an atlas can then be extended to a maximal smooth atlas by including all possible charts which satisfy the compatibility condition with the original maps. -
Nominations for President
ISSN 0002-9920 (print) ISSN 1088-9477 (online) of the American Mathematical Society September 2013 Volume 60, Number 8 The Calculus Concept Inventory— Measurement of the Effect of Teaching Methodology in Mathematics page 1018 DML-CZ: The Experience of a Medium- Sized Digital Mathematics Library page 1028 Fingerprint Databases for Theorems page 1034 A History of the Arf-Kervaire Invariant Problem page 1040 About the cover: 63 years since ENIAC broke the ice (see page 1113) Solve the differential equation. Solve the differential equation. t ln t dr + r = 7tet dt t ln t dr + r = 7tet dt 7et + C r = 7et + C ln t ✓r = ln t ✓ WHO HAS THE #1 HOMEWORK SYSTEM FOR CALCULUS? THE ANSWER IS IN THE QUESTIONS. When it comes to online calculus, you need a solution that can grade the toughest open-ended questions. And for that there is one answer: WebAssign. WebAssign’s patent pending grading engine can recognize multiple correct answers to the same complex question. Competitive systems, on the other hand, are forced to use multiple choice answers because, well they have no choice. And speaking of choice, only WebAssign supports every major textbook from every major publisher. With new interactive tutorials and videos offered to every student, it’s not hard to see why WebAssign is the perfect answer to your online homework needs. It’s all part of the WebAssign commitment to excellence in education. Learn all about it now at webassign.net/math. 800.955.8275 webassign.net/math WA Calculus Question ad Notices.indd 1 11/29/12 1:06 PM Notices 1051 of the American Mathematical Society September 2013 Communications 1048 WHAT IS…the p-adic Mandelbrot Set? Joseph H. -
Finite Group Actions on Kervaire Manifolds 3
FINITE GROUP ACTIONS ON KERVAIRE MANIFOLDS DIARMUID CROWLEY AND IAN HAMBLETON M4k+2 Abstract. Let K be the Kervaire manifold: a closed, piecewise linear (PL) mani- fold with Kervaire invariant 1 and the same homology as the product S2k+1 × S2k+1 of M4k+2 spheres. We show that a finite group of odd order acts freely on K if and only if 2k+1 2k+1 it acts freely on S × S . If MK is smoothable, then each smooth structure on M j M4k+2 K admits a free smooth involution. If k 6= 2 − 1, then K does not admit any M30 M62 free TOP involutions. Free “exotic” (PL) involutions are constructed on K , K , and M126 M30 Z Z K . Each smooth structure on K admits a free /2 × /2 action. 1. Introduction One of the main themes in geometric topology is the study of smooth manifolds and their piece-wise linear (PL) triangulations. Shortly after Milnor’s discovery [54] of exotic smooth 7-spheres, Kervaire [39] constructed the first example (in dimension 10) of a PL- manifold with no differentiable structure, and a new exotic smooth 9-sphere Σ9. The construction of Kervaire’s 10-dimensional manifold was generalized to all dimen- sions of the form m ≡ 2 (mod 4), via “plumbing” (see [36, §8]). Let P 4k+2 denote the smooth, parallelizable manifold of dimension 4k+2, k ≥ 0, constructed by plumbing two copies of the the unit tangent disc bundle of S2k+1. The boundary Σ4k+1 = ∂P 4k+2 is a smooth homotopy sphere, now usually called the Kervaire sphere. -
Mapping Surgery to Analysis III: Exact Sequences
K-Theory (2004) 33:325–346 © Springer 2005 DOI 10.1007/s10977-005-1554-7 Mapping Surgery to Analysis III: Exact Sequences NIGEL HIGSON and JOHN ROE Department of Mathematics, Penn State University, University Park, Pennsylvania 16802. e-mail: [email protected]; [email protected] (Received: February 2004) Abstract. Using the constructions of the preceding two papers, we construct a natural transformation (after inverting 2) from the Browder–Novikov–Sullivan–Wall surgery exact sequence of a compact manifold to a certain exact sequence of C∗-algebra K-theory groups. Mathematics Subject Classifications (1991): 19J25, 19K99. Key words: C∗-algebras, L-theory, Poincare´ duality, signature operator. This is the final paper in a series of three whose objective is to construct a natural transformation from the surgery exact sequence of Browder, Novikov, Sullivan and Wall [17,21] to a long exact sequence of K-theory groups associated to a certain C∗-algebra extension; we finally achieve this objective in Theorem 5.4. In the first paper [5], we have shown how to associate a homotopy invariant C∗-algebraic signature to suitable chain complexes of Hilbert modules satisfying Poincare´ duality. In the second paper, we have shown that such Hilbert–Poincare´ complexes arise natu- rally from geometric examples of manifolds and Poincare´ complexes. The C∗-algebras that are involved in these calculations are analytic reflections of the equivariant and/or controlled structure of the underlying topology. In paper II [6] we have also clarified the relationship between the analytic signature, defined by the procedure of paper I for suitable Poincare´ com- plexes, and the analytic index of the signature operator, defined only for manifolds. -
Browder's Theorem and Manifolds with Corners
Browder’s theorem and manifolds with corners Duality and the Wu classes. The “Spanier-Whitehead dual” of a spectrum X is the function spectrum (in which S denotes the sphere spectrum) DX = F (X, S) (which exists by Brown representability). It comes equipped with an “evaluation” pairing DX ∧ X → S. Write H∗(−) for homology with F2 coefficients. If X is finite, then the induced pairing H−∗(DX) ⊗ H∗(X) → F2 is perfect, so there is an isomorphism Hi(X) → Hom(H−i(DX), F2) which may be rewritten using the universal coefficient theorem as i −i Hom(H (X), F2) → H (DX) A Steenrod operation θ induces a contragredient action on the left, which coincides with the action of χθ on the right. Here χ is the Hopf conjugation on the Steenrod algebra. The map χ is an algebra anti-automorphism and an involution, and is characterized on the total Steenod square by the identity of operators χSq = Sq−1 because of the form of the Milnor diagonal. ∞ If M is a closed smooth m manifold and X = Σ M+, then the Thom spectrum M ν of the stable normal bundle (normalized to have formal dimension −m) furnishes the Spanier-Whitehead dual of X. This is “Milnor-Spanier” or “Atiyah” duality. Poincar´eduality is given by the composite isomorphism m−i −∪U −i ν =∼ H (M) −→ H (M ) ←− Hi(M) where U ∈ H−m(M ν) is the Thom class. 0 The rather boring collapse map M+ → S dualizes to a much more interesting map ι : S0 → M ν, which in cohomology induces the map ι∗ : x ∪ U 7→ hx, [M]i k By Poincar´eduality, for each k there is a unique class vk ∈ H (M) m−k k such that for any x ∈ H (M), hSq x, [M]i = hxvk, [M]i. -
The Arf-Kervaire Invariant Problem in Algebraic Topology: Introduction
THE ARF-KERVAIRE INVARIANT PROBLEM IN ALGEBRAIC TOPOLOGY: INTRODUCTION MICHAEL A. HILL, MICHAEL J. HOPKINS, AND DOUGLAS C. RAVENEL ABSTRACT. This paper gives the history and background of one of the oldest problems in algebraic topology, along with a short summary of our solution to it and a description of some of the tools we use. More details of the proof are provided in our second paper in this volume, The Arf-Kervaire invariant problem in algebraic topology: Sketch of the proof. A rigorous account can be found in our preprint The non-existence of elements of Kervaire invariant one on the arXiv and on the third author’s home page. The latter also has numerous links to related papers and talks we have given on the subject since announcing our result in April, 2009. CONTENTS 1. Background and history 3 1.1. Pontryagin’s early work on homotopy groups of spheres 3 1.2. Our main result 8 1.3. The manifold formulation 8 1.4. The unstable formulation 12 1.5. Questions raised by our theorem 14 2. Our strategy 14 2.1. Ingredients of the proof 14 2.2. The spectrum Ω 15 2.3. How we construct Ω 15 3. Some classical algebraic topology. 15 3.1. Fibrations 15 3.2. Cofibrations 18 3.3. Eilenberg-Mac Lane spaces and cohomology operations 18 3.4. The Steenrod algebra. 19 3.5. Milnor’s formulation 20 3.6. Serre’s method of computing homotopy groups 21 3.7. The Adams spectral sequence 21 4. Spectra and equivariant spectra 23 4.1. -
And Free Cyclic Group Actions on Homotopy Spheres
TRANSACTIONS OF THE AMERICAN MATHEMATICAL SOCIETY Volume 220, 1976 DECOMPOSABILITYOF HOMOTOPYLENS SPACES ANDFREE CYCLICGROUP ACTIONS ON HOMOTOPYSPHERES BY KAI WANG ABSTRACT. Let p be a linear Zn action on C and let p also denote the induced Z„ action on S2p~l x D2q, D2p x S2q~l and S2p~l x S2q~l " 1m_1 where p = [m/2] and q = m —p. A free differentiable Zn action (£ , ju) on a homotopy sphere is p-decomposable if there is an equivariant diffeomor- phism <t>of (S2p~l x S2q~l, p) such that (S2m_1, ju) is equivalent to (£(*), ¿(*)) where S(*) = S2p_1 x D2q U^, D2p x S2q~l and A(<P) is a uniquely determined action on S(*) such that i4(*)IS p~l XD q = p and A(Q)\D p X S = p. A homotopy lens space is p-decomposable if it is the orbit space of a p-decomposable free Zn action on a homotopy sphere. In this paper, we will study the decomposabilities of homotopy lens spaces. We will also prove that for each lens space L , there exist infinitely many inequivalent free Zn actions on S m such that the orbit spaces are simple homotopy equiva- lent to L 0. Introduction. Let A be the antipodal map and let $ be an equivariant diffeomorphism of (Sp x Sp, A) where A(x, y) = (-x, -y). Then there is a uniquely determined free involution A($) on 2(4>) where 2(4») = Sp x Dp+1 U<¡,Dp+l x Sp such that the inclusions S" x Dp+l —+ 2(d>), Dp+1 x Sp —*■2(4>) are equi- variant. -
A Topologist's View of Symmetric and Quadratic
1 A TOPOLOGIST'S VIEW OF SYMMETRIC AND QUADRATIC FORMS Andrew Ranicki (Edinburgh) http://www.maths.ed.ac.uk/eaar Patterson 60++, G¨ottingen,27 July 2009 2 The mathematical ancestors of S.J.Patterson Augustus Edward Hough Love Eidgenössische Technische Hochschule Zürich G. H. (Godfrey Harold) Hardy University of Cambridge Mary Lucy Cartwright University of Oxford (1930) Walter Kurt Hayman Alan Frank Beardon Samuel James Patterson University of Cambridge (1975) 3 The 35 students and 11 grandstudents of S.J.Patterson Schubert, Volcker (Vlotho) Do Stünkel, Matthias (Göttingen) Di Möhring, Leonhard (Hannover) Di,Do Bruns, Hans-Jürgen (Oldenburg?) Di Bauer, Friedrich Wolfgang (Frankfurt) Di,Do Hopf, Christof () Di Cromm, Oliver ( ) Di Klose, Joachim (Bonn) Do Talom, Fossi (Montreal) Do Kellner, Berndt (Göttingen) Di Martial Hille (St. Andrews) Do Matthews, Charles (Cambridge) Do (JWS Casels) Stratmann, Bernd O. (St. Andrews) Di,Do Falk, Kurt (Maynooth ) Di Kern, Thomas () M.Sc. (USA) Mirgel, Christa (Frankfurt?) Di Thirase, Jan (Göttingen) Di,Do Autenrieth, Michael (Hannover) Di, Do Karaschewski, Horst (Hamburg) Do Wellhausen, Gunther (Hannover) Di,Do Giovannopolous, Fotios (Göttingen) Do (ongoing) S.J.Patterson Mandouvalos, Nikolaos (Thessaloniki) Do Thiel, Björn (Göttingen(?)) Di,Do Louvel, Benoit (Lausanne) Di (Rennes), Do Wright, David (Oklahoma State) Do (B. Mazur) Widera, Manuela (Hannover) Di Krämer, Stefan (Göttingen) Di (Burmann) Hill, Richard (UC London) Do Monnerjahn, Thomas ( ) St.Ex. (Kriete) Propach, Ralf ( ) Di Beyerstedt, Bernd