E Modules for Abelian Hopf Algebras 1974: [Papers]/ IMPRINT Mexico, D.F
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llr ~ 1?J STATUS TYPE OCLC# Submitted 02/26/2019 Copy 28784366 IIIIIII IIIII IIIII IIIII IIIII IIIII IIIII IIIII IIIII IIII IIII SOURCE REQUEST DATE NEED BEFORE 193985894 ILLiad 02/26/2019 03/28/2019 BORROWER RECEIVE DATE DUE DATE RRR LENDERS 'ZAP, CUY, CGU BIBLIOGRAPHIC INFORMATION LOCAL ID AUTHOR ARTICLE AUTHOR Ravenel, Douglas TITLE Conference on Homotopy Theory: Evanston, Ill., ARTICLE TITLE Dieudonne modules for abelian Hopf algebras 1974: [papers]/ IMPRINT Mexico, D.F. : Sociedad Matematica Mexicana, FORMAT Book 1975. EDITION ISBN VOLUME NUMBER DATE 1975 SERIES NOTE Notas de matematica y simposia ; nr. 1. PAGES 177-183 INTERLIBRARY LOAN INFORMATION ALERT AFFILIATION ARL; RRLC; CRL; NYLINK; IDS; EAST COPYRIGHT US:CCG VERIFIED <TN:1067325><0DYSSEY:216.54.119.128/RRR> MAX COST OCLC IFM - 100.00 USD SHIPPED DATE LEND CHARGES FAX NUMBER LEND RESTRICTIONS EMAIL BORROWER NOTES We loan for free. Members of East, RRLC, and IDS. 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Toda correspondencia debe enviarse a: "NOTAS DE MATEMATICAS Y SIMPOSIA" COMITE EDITORIAL Apartado Postal 14-740 Mexico 14, D.F., Mexico Publicaci6n de la Sociedad Matematica Mexicana con el patr2 cinio del Programa Nacional de Formaci6n de Profesores de la A,N,U.I.E.S. y del Centro de Investigaci6n del I.P.N. SOCIEDAD MATEMATICA MEXICANA Mexico, D. F., 1975 ;.. V '1 ' "" A. 612 .7 CON'rENIOO C67 1974 Lista de Participantes . r.:/, TH VII Lista de Colaboradores. VIII DAVIS, D.M.: Introducci6~ IX DAVIS, D.M.: Problemas . 1 CONFERENC IAS BROWN, E.H., Jr. and PETERSON, F.P.: H* (MO) as an algebra over the Steenrod algebra .... 11 , . f 8l+7 DAVIS, D.M.: T h e immersion conJecture or JR 21 GLOVER, H.H. and MISLIN, G.: V~ctor fields on 2-equivalent manifolds 29 JOHNSON, D.C., MILLER, H.R., WILSON, W.S. and ZAHLER,R.S.: Boundary homomorphisms in the generalized Adams spectral sequence and the nontriviality of infinitely many yt in stable homotopy .... 47 KAHN, D.S.: Homology of the Barratt-Eccles decomposition maps 60 LIULEVICIUS, A.: On the birth and death of elements in complex cobordism .•........ 78 MA1'H· MAHOWALD, M.: On the unstable J-homomorphism 99 STA'T, \.\?,RARY MAY, J.P.: Problems in infinite loop space theory 106 MILGRAM, R.J.: The Steenrod algebra and its dual for connective K-theory 127 1 MILLER, H.R. and WILSON, W.S.: On Novikov's Ext modulo an invariant prime ideal .. 159 MOORE, J.C.: An algebraic version of the incompressibility theorem of S. Weingram 167 RAVENEL, D.C.: Dieudonne modules for abelian Hopf algebras 177 n: '~ DIEUDONNE MODULES FOR ABELIAN HOPF ALGEBRAS Preliminary Report in Honor of SAMUEL EILENBERG Douglas c. Ravenel (*) By Abelian Hopf algebra we mean graded connected biassocia tive strictly bi-commutative Hopf algebra of finite type over a perfect field k of characteristic p. Let A denote the cate gory of such objects. ~ is known to be abelian ([12]) and our purpose here is to show that it is isomorphic to a certain cate gory of modules. An analogous theorem for the nongraded case was proved long ago by Dieudonne, and the modules that he used have been studied extensively (see [l], Chapter v, and [4]). I am grateful to Bill Singer for first bringing this work to my attention and suggesting the problem of carrying it over to the graded case. The ring D in question is a noncommutative power series over W(k) (the Witt ring of k) in two variables F and V subject to the relations FV = VF = p Fw = w<J F, vwcr = wv *) ( Research partially supported by N.S.F. 178 179 7 for w E W(k), where wcr denotes the action of the Frobenius established by showing that the endomorphism ring of H*(BU;k) automorphism of k lifted to W(k). acts canonically on any abelian Hopf algebra. Part (b) follows In our case we will obtain modules over a commutative graded from the fact that a Hopf algebra map sends primitives to primi ring E = W(k) [[F,V]]/(FV-p) where dim F = 1, dim V = -1.. F tives. Part (c) is trivial. will be seen to correspond to the Frobenius endomorphism of a We now construct a set of projective generators for TA. 1 Hopf algebra A which sends x EA to xP, while V corresponds Let be k[b ,b , ... ,bn1 with dim b, = i and coproduct Bn E ~ 1 2 l. to the dual of F, commonly known as the Verschiebung. .pb, = b where bo = 1. Let w be the type 1 factor l. L s®bt s+t=i n The relation between abelian Hopf algebras and E-modules of B It is a polynomial algebra k[w ,w , ... ,w J with pn O 1 n will be described in Theorem 3" below, which is our main result. dim w, = pi. The coproduct is obtained lifting to W(k) and l. Our first result is a decomposition theorem. m , m-i defining the Witt polynomials f (w) = p o '.S_ m '.S, n, to m L 1.wf i=O Definition. Let n be an integer prime to p. An Abelian be primitive. Hopf algebra is of !Y£§_ n if each of its primitives and gener- i Theorem 2. w is a projective object in A and its dual for some i. Let T Ac A denote the n ators has dimension np n W* is therefore injective. full subcategory -,f l:yp2 n Abelian Hopf algebras. n Proof. Let S be the simple object k1x 7/xP, dim x r. Theorem 1.. There is a canonical categorical splitting r " r- r r Any Abelian Hopf algebra can be built up out of these simple A~ TA, i.e. TT n (n,p)=l- objects by multiple extensions, so it suffices to show a) Every Abelian Hopf algebra is canonically a direct 1 ExtA (w ,S) = O which is a simple calculation. n r \Jr, product of type n Abelian Hopf algebras. Now let Yi c T A denote the full subcategory whose objects b) There are no nontrivial maps between a type n Hopf 1 are the W. Let FW denote the category of contravariant algebra and a type m Hopf algebra for m ~ n. n - funccors from w to the category of finite W(k) modules. c) Moreover, T A T A n 1 n V This category is abelian. We define a functor Such a decomposition is well-known for the Hopf algebra D: T A-FW H*(BU;k) (see [3] for example) The general decomposition is - 1 - 180 181 by to the dual endomorphism, i.e. the Verschiebung. _!2(A) (Wn) Hom (W ,A) To make this more concise let E+ denote the where A is A n __Q 0 projective and A is polynomial. (If A is not finitely gen- 1 Now we can state our main result: erated, one can still construct and A and but they need 0 Al Theorem 3. The functor _!2 defined above is an equivalence not be of finite type). of abelian categories. This is a consequence of 2 The proof is analogous to that of Theorem V, §1,4.3 of [l]. Theorem 6. ExtA(B,A) O for all A iff B is polyno- Theorem 3 can be described in a more useful way by analyzing mial. the structure of W. Let V : w l<--w be the inclusion and n n- n We will conclude by identifying some well-known Hopf alge- let F W --w be defined by F (w.) WP Note that n n+l n n l i-1 bra functors wit~ standard functors from homological algebra. V F = F V p. Then we have n n-1 n n+l + It is convenient at this point to embed EO in ~, the full Lemma 4. The endomorphism ring of w is W(k) /pn+l and n category of graded E-modules and maps of all degrees. Hence for these endomorphisms along with the F and V generate all of M , N E E , Hom ( M, N) n n - E is also an E-module. Moreover, if N is the morphisms of W. nonnegative and M does not have any generators in positive dimensions then HomE(M,N) will also be nonnegatively graded. Hence Theorem 3 can be paraphrased as Define modules P = E/VE, R = E/FE. Theorem 3'. A type 1 Abelian Hopf algebra is characterized Theorem 7. Let AET A. Then Hom (P,C(A)) is isomorphic by a sequence of W(k) modules W (A) = Hom(W ,A) and maps 1 E n n to the abelian restricted Lie algebra of primitives of A (where F : W (A)--W (A) and V : W (A)-W (A) where n n n+ 1 n n n-1 VnFn-1 F corresponds to the restriction), and Ext~(T,C(A)) is isomer F nv n+l p.