COMPUTING WITH HOMOTOPY 1- AND 2-TYPES WHY? HOW? Graham Ellis NUI Galway, Ireland
|
|
- Eugene Small
- 8 years ago
- Views:
Transcription
1 COMPUTING WITH HOMOTOPY 1- AND 2-TYPES WHY? HOW? Graham Ellis NUI Galway, Ireland
2 Why: 1. potential applications to data analysis 2. examples for generating theory How: 3. discrete Morse theory 4. homological perturbation
3 An n-type is a CW complex X with π i X = 0 for i > n.
4 An n-type is a CW complex X with π i X = 0 for i > n. A connected 1-type is modelled by the fundamental group π 1 X.
5 An n-type is a CW complex X with π i X = 0 for i > n. A connected 1-type is modelled by the fundamental group π 1 X. A connected 2-type is modelled by the homomorphism : π 2 (X,X 1 ) π 1 X 1 and action of π 1 X 1 on π 2 (X,X 1 ). The algebraic abstraction is a crossed module.
6 A filtered chain complex over a field C 1 C 2 C 3 C 4 induces for s t. ι s t n : H n (C s ) H n (C t ) The Persistent Betti numbers are β s t n = rank(ι s t n ) s t β s t n = 0 s > t.
7 β n bar code has β s,t n horizontal lines from column s to column t (β s t 2 ) =
8 1. Data Analysis Toy data points: v 1,v 2,...,v 72 R
9 1. Data Analysis Toy data points: v 1,v 2,...,v 72 R generated from
10 Fix a sequence of real numbers ǫ 1 < ǫ 2 < < ǫ T. The Rips simplicial complex X t has vertex set V = {v 1,...,v 72 }. n-simplices the subsets σ V with n+1 vertices and v v ǫ t for all v,v σ.
11 Persistent β 0 for C (X ):
12 Persistent β 1 for C (X ):
13 Data Model: A homotopy retract Y X 20
14 Data Model: A homotopy retract Y X 20 Y S 1 S 1
15 Different toy data: v 1,v 2,...,v 256 R 9
16 Different toy data: v 1,v 2,...,v 256 R 9 generated from
17 β 0 and β 1 bar codes for the 256 patches:
18 Data Model: A homotopy retract Y X 9 with π 1 Y = x,y xyx 1 y and just four (critical) cells e 0, e 1 1, e1 2, e2.
19 Data Model: A homotopy retract Y X 9 with π 1 Y = x,y xyx 1 y and just four (critical) cells e 0, e 1 1, e1 2, e2. Lyndon s theorem on one-relator groups implies π 2 Y = 0,
20 Data Model: A homotopy retract Y X 9 with π 1 Y = x,y xyx 1 y and just four (critical) cells e 0, e 1 1, e1 2, e2. Lyndon s theorem on one-relator groups implies and Y Klein Bottle. π 2 Y = 0,π n Y = 0 for n 2
21 Data Model: A homotopy retract Y X 9 with π 1 Y = x,y xyx 1 y and just four (critical) cells e 0, e 1 1, e1 2, e2. Lyndon s theorem on one-relator groups implies and Y Klein Bottle. π 2 Y = 0,π n Y = 0 for n 2 Caveat: [Kan-Thurston] For any space X there is a map K(G,1) X inducing H (K(G,1)) = H (X).
22 3-dimensional Euclidean data
23
24 Proposition: The alpha carbon atoms of the Thermus Thermophilus protein determine a knot K with peripheral system π 1 ( K) = a,b aba 1 b 1 π 1 (R 3 \K) = x,y xyx = yxy a x 2 yx 2 y b x. gap> K:=ReadPDBfile("1V2X.pdb"); Pure permutahedral complex of dimension 3 gap> Y:=RegularCWComplex(PureComplexComplement(K));; Regular CW-complex of dimension 3 gap> i:=boundary(y); Map of regular CW-complexes gap> phi:=fundamentalgroup(i,22495); [ f1, f2 ] -> [ f1^-3*f2*f1^2*f2*f1, f1 ]
25 A number of useful invariants are easily computed from a presentation of the fundamental group.
26 A number of useful invariants are easily computed from a presentation of the fundamental group. Computing low-index groups of a finitely presented group G Index n subgroup H G corresponds to a homomorphism G S n into the group of permutations of X = {gh g G}.
27 A number of useful invariants are easily computed from a presentation of the fundamental group. Computing low-index groups of a finitely presented group G Index n subgroup H G corresponds to a homomorphism G S n into the group of permutations of X = {gh g G}. Only finitely many such homomorphisms.
28 A number of useful invariants are easily computed from a presentation of the fundamental group. Computing low-index groups of a finitely presented group G Index n subgroup H G corresponds to a homomorphism G S n into the group of permutations of X = {gh g G}. Only finitely many such homomorphisms. Index n subgroups H G are finitely presented (Reidemeister- Schreier).
29 Proposition (Brendel, E, Juda, Mrozek ) The abelian invariants of subgroups G π 1 (R 3 \K) of index 7 distinguish between the ambient isotopy classes of prime knots with fourteen or fewer crossings, up to chirality.
30 A more quickly computed invariant: Construct the link K red K blue as a voxel image and then X = [0,1] 3 \(K red K blue ) as a CW complex with cells.
31 A more quickly computed invariant: Construct the link K red K blue as a voxel image and then X = [0,1] 3 \(K red K blue ) as a CW complex with cells. Compute π 1 X = x 1,x 2,x 3 : r 1,r 2,r 3,r 4.
32 A more quickly computed invariant: For generators α red,α blue H 1 (X,Z), β H 2 (X,Z) α red α blue = β r r 4π K red Kblue r r 3 dr dr = 6β
33 A more quickly computed invariant: For generators α red,α blue H 1 (X,Z), β H 2 (X,Z) α red α blue = β r r 4π K red Kblue r r 3 dr dr = 6β is instantly computed from P = x 1,x 2,x 3 : r 1,r 2,r 3,r 4 and : K(P) K(P) K(P).
34 For P = x,y : xyx = yxy the diagonal is given by: y x y y x y y x y y x y x x x x x y x x y x y y
35 For P = x,y : xyx = yxy the diagonal is given by: y x y y x y y x y y x y x x x x x y x x y x y y Only need orientations of quadrilaterals for cup product.
36 A more challenging invariant to compute: L = L = Y = R 3 \L Y = R 3 \L
37 A more challenging invariant to compute: L = L = Y = R 3 \L Y = R 3 \L H 3 ( π 1 Y/[[π 1 Y,π 1 Y],π 1 Y],Z) = Z 40 H 3 ( π 1 Y /[[π 1 Y,π 1 Y ],π 1 Y ],Z) = Z 6
38 2. A computation leading to some theory A crystallographic group is a discrete subgroup G < Isom(R n ) with finite index translation subgroup T G.
39 2. A computation leading to some theory A crystallographic group is a discrete subgroup G < Isom(R n ) with finite index translation subgroup T G. Set γ 1 T = T, γ i+1 T = [γ i T,G].
40 2. A computation leading to some theory A crystallographic group is a discrete subgroup G < Isom(R n ) with finite index translation subgroup T G. Set γ 1 T = T, γ i+1 T = [γ i T,G]. β s,t n = rank(h n (G/γ t T,F) H n (G/γ s T,F))
41 Illustration t: R R,x x +1 g: R R,x x G = t,g : g 2 = 1,tg = gt 1 = D
42 Illustration t: R R,x x +1 g: R R,x x G = t,g : g 2 = 1,tg = gt 1 = D G/γ n T = D 2 n 1
43 Illustration t: R R,x x +1 g: R R,x x G = t,g : g 2 = 1,tg = gt 1 = D G/γ n T = D 2 n 1 β 3 bar code
44 Proposition (E) Let G be an n-dimensional crystallographic group and let F = F p. We have H i (G/γ c T,F) = H i (G/γ c+d T,F) for all i 0,c k if:
45 Proposition (E) Let G be an n-dimensional crystallographic group and let F = F p. We have H i (G/γ c T,F) = H i (G/γ c+d T,F) for all i 0,c k if: P = G/T is a p-group;
46 Proposition (E) Let G be an n-dimensional crystallographic group and let F = F p. We have H i (G/γ c T,F) = H i (G/γ c+d T,F) for all i 0,c k if: P = G/T is a p-group; there exists an integer k 1 such that T/γ c+1 T is an n-generator abelian p-group for c k and, in the case p = 2, T/γ c+1 T is a direct product of cyclic groups of exponent > 2; and
47 Proposition (E) Let G be an n-dimensional crystallographic group and let F = F p. We have H i (G/γ c T,F) = H i (G/γ c+d T,F) for all i 0,c k if: P = G/T is a p-group; there exists an integer k 1 such that T/γ c+1 T is an n-generator abelian p-group for c k and, in the case p = 2, T/γ c+1 T is a direct product of cyclic groups of exponent > 2; and γ c T Z F and γ c+d T Z F are isomorphic FP-modules for all c k.
48 Proposition (E) Let G be an n-dimensional crystallographic group and let F = F p. We have H i (G/γ c T,F) = H i (G/γ c+d T,F) for all i 0,c k if: P = G/T is a p-group; there exists an integer k 1 such that T/γ c+1 T is an n-generator abelian p-group for c k and, in the case p = 2, T/γ c+1 T is a direct product of cyclic groups of exponent > 2; and γ c T Z F and γ c+d T Z F are isomorphic FP-modules for all c k. So a finite computation can yield the mod-p homology of an infinite family of groups.
49 3. Discrete vector fields A finite regular CW complex is readily stored on a computer
50 A simple homotopy collapse X e n e n 1 ց X e n 1 e n X
51 A simple homotopy collapse X e n e n 1 ց X e n 1 e n X is stored in computer as a pair (e n 1,e n ) or arrow e n 1 e n.
52
53 A discrete vector field is a collection of arrows e n 1 e n with e n 1 in the boundary of e n and with any cell involved in at most one arrow. It is admissible if there is no chain (e n 1 1,e n 1 ),(en 1 2,e n 2 ),(en 1 3,e n 3 ), with each e n 1 i+1 in the boundary of en i and with infinitely many (not necessarily distinct) terms to the right.
54 A regular CW complex X with admissible discrete vector field represents a homotopy equivalence X Y where Y is a CW complex whose cells correspond to those of X that are neither source nor target of any arrow.
55 A regular CW complex X with admissible discrete vector field represents a homotopy equivalence X Y where Y is a CW complex whose cells correspond to those of X that are neither source nor target of any arrow. Such cells of X are critical.
56 A regular CW complex X with admissible discrete vector field represents a homotopy equivalence X Y where Y is a CW complex whose cells correspond to those of X that are neither source nor target of any arrow. Such cells of X are critical. An admissible discrete vector field on X 2 with just one critical 0-cell represents a presentation for π 1 X.
57 A G-CW complex is a CW complex X with an action of a group G that permutes cells. A computer representation is straighforward if X is regular and has only finitely many orbits of cells.
58 A G-CW complex is a CW complex X with an action of a group G that permutes cells. A computer representation is straighforward if X is regular and has only finitely many orbits of cells. C (X) is an exact chain complex of free ZG-modules
59 A G-CW complex is a CW complex X with an action of a group G that permutes cells. A computer representation is straighforward if X is regular and has only finitely many orbits of cells. C (X) is an exact chain complex of free ZG-modules and moreover a resolution with homotopy h : C (X) C +1 (X) dh+hd = 1 if G acts freely and X has a discrete vector field with just one critical cell.
60 A G-CW complex is a CW complex X with an action of a group G that permutes cells. A computer representation is straighforward if X is regular and has only finitely many orbits of cells. C (X) is an exact chain complex of free ZG-modules and moreover a resolution with homotopy h : C (X) C +1 (X) dh+hd = 1 if G acts freely and X has a discrete vector field with just one critical cell. C (Nerve(G)) C (X/G)
61 G = a,b aba = b a: R 2 R 2,(x,y) (x +1, y) b: R 2 R 2,(x,y) (x,y +1) X = R 2 X/G C (Nerve(G)) C (X/G)
62 G = a,b aba = b a: R 2 R 2,(x,y) (x +1, y) b: R 2 R 2,(x,y) (x,y +1) X = R 2 X/G C (Nerve(G)) C (X/G)
63 4. Perturbations and homology of 2-types Joint with Le Van Luyen
64 Theorem (JHC Whitehead): There is an exact sequence of groups π 2 (Y) π 2 (X) π 2 (X,Y) in which is a crossed module: π 1 (Y) π 1 (X) A crossed module is a group homomorphism : M G with action (g,m) g m statisfying ( g m) = g (m)g 1 m m = mm m 1
65 Theorem (JHC Whitehead): There is an exact sequence of groups π 2 (Y) π 2 (X) π 2 (X,Y) in which is a crossed module: π 1 (Y) π 1 (X) A crossed module is a group homomorphism : M G with action (g,m) g m statisfying ( g m) = g (m)g 1 m m = mm m 1 We define π 1 ( ) = G/image π 2 ( ) = ker.
66 Taking Y = X 1 we get Whitehead s functor Ho(CW spaces) Σ 1 (crossed modules) which is faithful on homotopy types X with π n X = 0 for n 1,2. Σ 1 is localization with respect to quasi-isomorphisms
67 Taking Y = X 1 we get Whitehead s functor Ho(CW spaces) Σ 1 (crossed modules) which is faithful on homotopy types X with π n X = 0 for n 1,2. Σ 1 is localization with respect to quasi-isomorphisms Let B(M G) denote a CW-space with π n X = 0 for n 1,2 that maps to.
68 : Q Aut(Q),g {x gxg 1 } is a crossed module for any group Q.
69 : Q Aut(Q),g {x gxg 1 } is a crossed module for any group Q. H 5 ( B(D 216 Aut(D 216 )), Z) = (Z2 ) 11 (Z 3 ) 2 gap> Q:=DihedralGroup(216);; gap> C:=AutoCrossedModule(Q);; gap> Homology(C,5); [ 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 18 ]
70 N : (crossed modules) (simplicial groups) Given : M G we consider the category A = M G s: A A, (m,g) (1,g) t: A A, (m,g) (1, (m)g) : A G A A, ((m,g),(m,g ) (m,( m) 1 g )
71 N : (crossed modules) (simplicial groups) Given : M G we consider the category A = M G s: A A, (m,g) (1,g) t: A A, (m,g) (1, (m)g) : A G A A, ((m,g),(m,g ) (m,( m) 1 g ) s, t, are group homomorphisms and A is a category internal to the category of groups. The nerve N(A) is thus a simplicial group.
72 B: (crossed modules) N (simplicial groups) N (bisimplicial sets) (simplicial sets)
73 B: (crossed modules) N (simplicial groups) F: (sets) (free abelian groups) N (bisimplicial sets) (simplicial sets)
74 B: (crossed modules) N (simplicial groups) F: (sets) (free abelian groups) N (bisimplicial sets) (simplicial sets) C (B( : M G)) is the total complex of the bicomplex: FN 2 N 2 (A) FN 2 N 1 (A) FN 2 N 0 (A) FN 1 N 2 (A) FN 1 N 1 (A) FN 1 N 0 (A) FN 0 N 2 (A) FN 0 N 1 (A) FN 0 N 0 (A)
75 The jth column FN (N j (A)) is the bar complex for the group N j (A).
76 The jth column FN (N j (A)) is the bar complex for the group N j (A). We could replace each column by R N j(a) ZNj (A) Z where R N j(a) is an arbitrary free ZN j (A)-resolution of Z.
77 The jth column FN (N j (A)) is the bar complex for the group N j (A). We could replace each column by R N j(a) ZNj (A) Z where R N j(a) is an arbitrary free ZN j (A)-resolution of Z. But the horizontally induced maps won t square to zero if the resolutions aren t functorial.
78 The jth column FN (N j (A)) is the bar complex for the group N j (A). We could replace each column by R N j(a) ZNj (A) Z where R N j(a) is an arbitrary free ZN j (A)-resolution of Z. But the horizontally induced maps won t square to zero if the resolutions aren t functorial. Homological Perturbation Lemma solves this problem by providing a filtered complex ZN (A) Z R N (A)
79 A homotopy equivalence data (L,d) p i (M,d), h ( ) consists of chain complexes L,M, quasi-isomorphisms i,p and a homotopy ip 1 = dh+hd. A perturbation on ( ) is a homomorphism ǫ: M M of degree 1 such that (d +ǫ) 2 = 0.
80 A homotopy equivalence data (L,d) p i (M,d), h ( ) consists of chain complexes L,M, quasi-isomorphisms i,p and a homotopy ip 1 = dh+hd. A perturbation on ( ) is a homomorphism ǫ: M M of degree 1 such that (d +ǫ) 2 = 0. Perturbation Lemma (M. Crainic 2004): If A = (1 ǫh) 1 ǫ exists then p (L,d i ) (M,d +ǫ), h ( ) is a homotopy equivalence data where i = i +hai, p = p +pah, h = h+hah, d = d +pai.
81 0 0 FN 2 N 2 (A) 0 FN 2 N 1 (A) FN 2 N 0 (A) 0 FN 1 N 2 (A) 0 FN 1 N 1 (A) 0 FN 1 N 0 (A) (M,d) 0 FN 0 N 2 (A) 0 FN 0 N 1 (A) 0 0 FN 0 N 0 (A) 0 R N 2(A) 2 Z 0 R N 1(A) 0 2 Z R N 0(A) 2 Z 0 R N 2(A) 1 Z 0 R N 1(A) 1 Z 0 R N 0(A) 1 Z (L,d) 0 N 2 (A) 0 N 1 (A) 0 N 0 (A)
82 FN 2 N 2 (A) FN 2 N 1 (A) FN 2 N 0 (A) FN 1 N 2 (A) FN 1 N 1 (A) FN 1 N 0 (A) (M,d +ǫ) FN 0 N 2 (A) FN 0 N 1 (A) FN 0 N 0 (A) R N 2(A) 2 Z R N 1(A) 2 Z R N 0(A) 2 Z R N 2(A) 1 Z R N 1(A) 1 Z R N 0(A) 1 Z N 2 (A) N 1 (A) N 0 (A) (L,d )
83 A morphism of crossed modules induces a group homomorphism on π 1 = coker( ) (1) and a π 1 -module homomorphism on π 2 = ker( ). (2) Quasi-isomorphsm is the equivalence relation generated by morphisms where (1) and (2) are isomorphisms. So is quasi-isomorphic to if there exists some sequence of quasi-isomorphisms k
84 : Q Aut(Q) gap> C:=AutoCrossedModule(DihedralGroup(216));; gap> Size(C); # = Q x Aut(Q) gap> IdQuasiCrossedModule(C); [ 72, 68 ]
85 : Q Aut(Q) gap> C:=AutoCrossedModule(DihedralGroup(216));; gap> Size(C); # = Q x Aut(Q) gap> IdQuasiCrossedModule(C); [ 72, 68 ] gap> D:=SmallQuasiCrossedModule(72,68); Crossed module
86 : Q Aut(Q) gap> C:=AutoCrossedModule(DihedralGroup(216));; gap> Size(C); # = Q x Aut(Q) gap> IdQuasiCrossedModule(C); [ 72, 68 ] gap> D:=SmallQuasiCrossedModule(72,68); Crossed module gap> Homology(D,5); [ 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 18 ]
87 A curiosity The crossed module : Z 2 0 yields a homotopy 2-type B = B( ) with π 2 (B) = Z 2, π k (B) = 0 for k 2.
88 A curiosity The crossed module : Z 2 0 yields a homotopy 2-type B = B( ) with π 2 (B) = Z 2, π k (B) = 0 for k 2. gap> B:=EilenbergMacLaneComplex(CyclicGroup(2),2,11);; gap> C:=ChainComplex(B);; gap> List([0..11],CK!.dimension); [ 1, 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024 ]
89 A curiosity The crossed module : Z 2 0 yields a homotopy 2-type B = B( ) with π 2 (B) = Z 2, π k (B) = 0 for k 2. gap> B:=EilenbergMacLaneComplex(CyclicGroup(2),2,11);; gap> C:=ChainComplex(B);; gap> List([0..11],CK!.dimension); [ 1, 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024 ] gap> D:=CoreducedChainComplex(C);; gap> List([0..10],D!.dimension); [ 1, 0, 1, 1, 2, 3, 5, 8, 13, 21, 34 ]
Computational homology of n-types
Computational homology of n-types Graham Ellis Graham Ellis, School of Mathematics, National University of Ireland, Galway Le Van Luyen Le Van Luyen, School of Mathematics, National University of Ireland,
More informationEffective homotopy of the fiber of a Kan fibration
Effective homotopy of the fiber of a Kan fibration Ana Romero and Francis Sergeraert 1 Introduction Inspired by the fundamental ideas of the effective homology method (see [5] and [4]), which makes it
More informationSolutions to TOPICS IN ALGEBRA I.N. HERSTEIN. Part II: Group Theory
Solutions to TOPICS IN ALGEBRA I.N. HERSTEIN Part II: Group Theory No rights reserved. Any part of this work can be reproduced or transmitted in any form or by any means. Version: 1.1 Release: Jan 2013
More informationGROUP ALGEBRAS. ANDREI YAFAEV
GROUP ALGEBRAS. ANDREI YAFAEV We will associate a certain algebra to a finite group and prove that it is semisimple. Then we will apply Wedderburn s theory to its study. Definition 0.1. Let G be a finite
More informationHow To Prove The Dirichlet Unit Theorem
Chapter 6 The Dirichlet Unit Theorem As usual, we will be working in the ring B of algebraic integers of a number field L. Two factorizations of an element of B are regarded as essentially the same if
More informationMathematics Course 111: Algebra I Part IV: Vector Spaces
Mathematics Course 111: Algebra I Part IV: Vector Spaces D. R. Wilkins Academic Year 1996-7 9 Vector Spaces A vector space over some field K is an algebraic structure consisting of a set V on which are
More informationI. GROUPS: BASIC DEFINITIONS AND EXAMPLES
I GROUPS: BASIC DEFINITIONS AND EXAMPLES Definition 1: An operation on a set G is a function : G G G Definition 2: A group is a set G which is equipped with an operation and a special element e G, called
More information(0, 0) : order 1; (0, 1) : order 4; (0, 2) : order 2; (0, 3) : order 4; (1, 0) : order 2; (1, 1) : order 4; (1, 2) : order 2; (1, 3) : order 4.
11.01 List the elements of Z 2 Z 4. Find the order of each of the elements is this group cyclic? Solution: The elements of Z 2 Z 4 are: (0, 0) : order 1; (0, 1) : order 4; (0, 2) : order 2; (0, 3) : order
More informationEXERCISES FOR THE COURSE MATH 570, FALL 2010
EXERCISES FOR THE COURSE MATH 570, FALL 2010 EYAL Z. GOREN (1) Let G be a group and H Z(G) a subgroup such that G/H is cyclic. Prove that G is abelian. Conclude that every group of order p 2 (p a prime
More informationClass One: Degree Sequences
Class One: Degree Sequences For our purposes a graph is a just a bunch of points, called vertices, together with lines or curves, called edges, joining certain pairs of vertices. Three small examples of
More informationChapter 7: Products and quotients
Chapter 7: Products and quotients Matthew Macauley Department of Mathematical Sciences Clemson University http://www.math.clemson.edu/~macaule/ Math 42, Spring 24 M. Macauley (Clemson) Chapter 7: Products
More informationON GENERALIZED RELATIVE COMMUTATIVITY DEGREE OF A FINITE GROUP. A. K. Das and R. K. Nath
International Electronic Journal of Algebra Volume 7 (2010) 140-151 ON GENERALIZED RELATIVE COMMUTATIVITY DEGREE OF A FINITE GROUP A. K. Das and R. K. Nath Received: 12 October 2009; Revised: 15 December
More informationG = G 0 > G 1 > > G k = {e}
Proposition 49. 1. A group G is nilpotent if and only if G appears as an element of its upper central series. 2. If G is nilpotent, then the upper central series and the lower central series have the same
More information4.1 Modules, Homomorphisms, and Exact Sequences
Chapter 4 Modules We always assume that R is a ring with unity 1 R. 4.1 Modules, Homomorphisms, and Exact Sequences A fundamental example of groups is the symmetric group S Ω on a set Ω. By Cayley s Theorem,
More informationNOTES ON CATEGORIES AND FUNCTORS
NOTES ON CATEGORIES AND FUNCTORS These notes collect basic definitions and facts about categories and functors that have been mentioned in the Homological Algebra course. For further reading about category
More informationMath 231b Lecture 35. G. Quick
Math 231b Lecture 35 G. Quick 35. Lecture 35: Sphere bundles and the Adams conjecture 35.1. Sphere bundles. Let X be a connected finite cell complex. We saw that the J-homomorphism could be defined by
More informationHow To Prove The Cellosauric Cardinal Compactness (For A Cardinal Cardinal Compact)
Cellular objects and Shelah s singular compactness theorem Logic Colloquium 2015 Helsinki Tibor Beke 1 Jiří Rosický 2 1 University of Massachusetts tibor beke@uml.edu 2 Masaryk University Brno rosicky@math.muni.cz
More informationADDITIVE GROUPS OF RINGS WITH IDENTITY
ADDITIVE GROUPS OF RINGS WITH IDENTITY SIMION BREAZ AND GRIGORE CĂLUGĂREANU Abstract. A ring with identity exists on a torsion Abelian group exactly when the group is bounded. The additive groups of torsion-free
More informationOn the existence of G-equivariant maps
CADERNOS DE MATEMÁTICA 12, 69 76 May (2011) ARTIGO NÚMERO SMA# 345 On the existence of G-equivariant maps Denise de Mattos * Departamento de Matemática, Instituto de Ciências Matemáticas e de Computação,
More informationQ-PERFECT GROUPS AND UNIVERSAL Q-CENTRAL EXTENSIONS
Publicacions Matemátiques, Vol 34 (1990), 291-297. Q-PERFECT GROUPS AND UNIVERSAL Q-CENTRAL EXTENSIONS RONALD BROWN Abstract Using results of Ellis-Rodríguez Fernández, an explicit description by generators
More informationHomological Algebra Workshop 02-03-15/06-03-15
Homological Algebra Workshop 02-03-15/06-03-15 Monday: Tuesday: 9:45 10:00 Registration 10:00 11:15 Conchita Martínez (I) 10:00 11:15 Conchita Martínez (II) 11:15 11:45 Coffee Break 11:15 11:45 Coffee
More informationChapter 13: Basic ring theory
Chapter 3: Basic ring theory Matthew Macauley Department of Mathematical Sciences Clemson University http://www.math.clemson.edu/~macaule/ Math 42, Spring 24 M. Macauley (Clemson) Chapter 3: Basic ring
More informationUniversitat de Barcelona
Universitat de Barcelona GRAU DE MATEMÀTIQUES Final year project Cohomology of Product Spaces from a Categorical Viewpoint Álvaro Torras supervised by Prof. Carles Casacuberta January 18, 2016 2 3 Introduction
More informationGROUPS ACTING ON A SET
GROUPS ACTING ON A SET MATH 435 SPRING 2012 NOTES FROM FEBRUARY 27TH, 2012 1. Left group actions Definition 1.1. Suppose that G is a group and S is a set. A left (group) action of G on S is a rule for
More informationElements of Abstract Group Theory
Chapter 2 Elements of Abstract Group Theory Mathematics is a game played according to certain simple rules with meaningless marks on paper. David Hilbert The importance of symmetry in physics, and for
More informationSOME PROPERTIES OF FIBER PRODUCT PRESERVING BUNDLE FUNCTORS
SOME PROPERTIES OF FIBER PRODUCT PRESERVING BUNDLE FUNCTORS Ivan Kolář Abstract. Let F be a fiber product preserving bundle functor on the category FM m of the proper base order r. We deduce that the r-th
More informationClassification of Bundles
CHAPTER 2 Classification of Bundles In this chapter we prove Steenrod s classification theorem of principal G - bundles, and the corresponding classification theorem of vector bundles. This theorem states
More informationBP-cohomology of mapping spaces from the classifying space of a torus to some p-torsion free space
BP-cohomology of mapping spaces from the classifying space of a torus to some p-torsion free space 1. Introduction Let p be a fixed prime number, V a group isomorphic to (Z/p) d for some integer d and
More informationChapter 7. Permutation Groups
Chapter 7 Permutation Groups () We started the study of groups by considering planar isometries In the previous chapter, we learnt that finite groups of planar isometries can only be cyclic or dihedral
More informationA REMARK ON ALMOST MOORE DIGRAPHS OF DEGREE THREE. 1. Introduction and Preliminaries
Acta Math. Univ. Comenianae Vol. LXVI, 2(1997), pp. 285 291 285 A REMARK ON ALMOST MOORE DIGRAPHS OF DEGREE THREE E. T. BASKORO, M. MILLER and J. ŠIRÁŇ Abstract. It is well known that Moore digraphs do
More informationMATRIX ALGEBRA AND SYSTEMS OF EQUATIONS. + + x 2. x n. a 11 a 12 a 1n b 1 a 21 a 22 a 2n b 2 a 31 a 32 a 3n b 3. a m1 a m2 a mn b m
MATRIX ALGEBRA AND SYSTEMS OF EQUATIONS 1. SYSTEMS OF EQUATIONS AND MATRICES 1.1. Representation of a linear system. The general system of m equations in n unknowns can be written a 11 x 1 + a 12 x 2 +
More informationNOTES ON LINEAR TRANSFORMATIONS
NOTES ON LINEAR TRANSFORMATIONS Definition 1. Let V and W be vector spaces. A function T : V W is a linear transformation from V to W if the following two properties hold. i T v + v = T v + T v for all
More informationFIBER BUNDLES AND UNIVALENCE
FIBER BUNDLES AND UNIVALENCE TALK BY IEKE MOERDIJK; NOTES BY CHRIS KAPULKIN This talk presents a proof that a universal Kan fibration is univalent. The talk was given by Ieke Moerdijk during the conference
More informationFOUNDATIONS OF ALGEBRAIC GEOMETRY CLASS 22
FOUNDATIONS OF ALGEBRAIC GEOMETRY CLASS 22 RAVI VAKIL CONTENTS 1. Discrete valuation rings: Dimension 1 Noetherian regular local rings 1 Last day, we discussed the Zariski tangent space, and saw that it
More informationCLUSTER ALGEBRAS AND CATEGORIFICATION TALKS: QUIVERS AND AUSLANDER-REITEN THEORY
CLUSTER ALGEBRAS AND CATEGORIFICATION TALKS: QUIVERS AND AUSLANDER-REITEN THEORY ANDREW T. CARROLL Notes for this talk come primarily from two sources: M. Barot, ICTP Notes Representations of Quivers,
More informationFIBRATION SEQUENCES AND PULLBACK SQUARES. Contents. 2. Connectivity and fiber sequences. 3
FIRTION SEQUENES ND PULLK SQURES RY MLKIEWIH bstract. We lay out some foundational facts about fibration sequences and pullback squares of topological spaces. We pay careful attention to connectivity ranges
More informationCOHOMOLOGY OF GROUPS
Actes, Congrès intern. Math., 1970. Tome 2, p. 47 à 51. COHOMOLOGY OF GROUPS by Daniel QUILLEN * This is a report of research done at the Institute for Advanced Study the past year. It includes some general
More informationTOPOLOGY OF SINGULAR FIBERS OF GENERIC MAPS
TOPOLOGY OF SINGULAR FIBERS OF GENERIC MAPS OSAMU SAEKI Dedicated to Professor Yukio Matsumoto on the occasion of his 60th birthday Abstract. We classify singular fibers of C stable maps of orientable
More informationPUTNAM TRAINING POLYNOMIALS. Exercises 1. Find a polynomial with integral coefficients whose zeros include 2 + 5.
PUTNAM TRAINING POLYNOMIALS (Last updated: November 17, 2015) Remark. This is a list of exercises on polynomials. Miguel A. Lerma Exercises 1. Find a polynomial with integral coefficients whose zeros include
More informationThe Open University s repository of research publications and other research outputs
Open Research Online The Open University s repository of research publications and other research outputs The degree-diameter problem for circulant graphs of degree 8 and 9 Journal Article How to cite:
More information4. FIRST STEPS IN THE THEORY 4.1. A
4. FIRST STEPS IN THE THEORY 4.1. A Catalogue of All Groups: The Impossible Dream The fundamental problem of group theory is to systematically explore the landscape and to chart what lies out there. We
More informationGroup Theory. Contents
Group Theory Contents Chapter 1: Review... 2 Chapter 2: Permutation Groups and Group Actions... 3 Orbits and Transitivity... 6 Specific Actions The Right regular and coset actions... 8 The Conjugation
More informationThe cover SU(2) SO(3) and related topics
The cover SU(2) SO(3) and related topics Iordan Ganev December 2011 Abstract The subgroup U of unit quaternions is isomorphic to SU(2) and is a double cover of SO(3). This allows a simple computation of
More informationLecture 18 - Clifford Algebras and Spin groups
Lecture 18 - Clifford Algebras and Spin groups April 5, 2013 Reference: Lawson and Michelsohn, Spin Geometry. 1 Universal Property If V is a vector space over R or C, let q be any quadratic form, meaning
More informationQuotient Rings and Field Extensions
Chapter 5 Quotient Rings and Field Extensions In this chapter we describe a method for producing field extension of a given field. If F is a field, then a field extension is a field K that contains F.
More information1 Local Brouwer degree
1 Local Brouwer degree Let D R n be an open set and f : S R n be continuous, D S and c R n. Suppose that the set f 1 (c) D is compact. (1) Then the local Brouwer degree of f at c in the set D is defined.
More informationGENERATING SETS KEITH CONRAD
GENERATING SETS KEITH CONRAD 1 Introduction In R n, every vector can be written as a unique linear combination of the standard basis e 1,, e n A notion weaker than a basis is a spanning set: a set of vectors
More informationGROUPS WITH TWO EXTREME CHARACTER DEGREES AND THEIR NORMAL SUBGROUPS
GROUPS WITH TWO EXTREME CHARACTER DEGREES AND THEIR NORMAL SUBGROUPS GUSTAVO A. FERNÁNDEZ-ALCOBER AND ALEXANDER MORETÓ Abstract. We study the finite groups G for which the set cd(g) of irreducible complex
More informationFINITE DIMENSIONAL ORDERED VECTOR SPACES WITH RIESZ INTERPOLATION AND EFFROS-SHEN S UNIMODULARITY CONJECTURE AARON TIKUISIS
FINITE DIMENSIONAL ORDERED VECTOR SPACES WITH RIESZ INTERPOLATION AND EFFROS-SHEN S UNIMODULARITY CONJECTURE AARON TIKUISIS Abstract. It is shown that, for any field F R, any ordered vector space structure
More information8.1 Examples, definitions, and basic properties
8 De Rham cohomology Last updated: May 21, 211. 8.1 Examples, definitions, and basic properties A k-form ω Ω k (M) is closed if dω =. It is exact if there is a (k 1)-form σ Ω k 1 (M) such that dσ = ω.
More information. 0 1 10 2 100 11 1000 3 20 1 2 3 4 5 6 7 8 9
Introduction The purpose of this note is to find and study a method for determining and counting all the positive integer divisors of a positive integer Let N be a given positive integer We say d is a
More informationA NOTE ON TRIVIAL FIBRATIONS
A NOTE ON TRIVIAL FIBRATIONS Petar Pavešić Fakulteta za Matematiko in Fiziko, Univerza v Ljubljani, Jadranska 19, 1111 Ljubljana, Slovenija petar.pavesic@fmf.uni-lj.si Abstract We study the conditions
More informationNotes on finite group theory. Peter J. Cameron
Notes on finite group theory Peter J. Cameron October 2013 2 Preface Group theory is a central part of modern mathematics. Its origins lie in geometry (where groups describe in a very detailed way the
More informationGalois representations with open image
Galois representations with open image Ralph Greenberg University of Washington Seattle, Washington, USA May 7th, 2011 Introduction This talk will be about representations of the absolute Galois group
More information2. Let H and K be subgroups of a group G. Show that H K G if and only if H K or K H.
Math 307 Abstract Algebra Sample final examination questions with solutions 1. Suppose that H is a proper subgroup of Z under addition and H contains 18, 30 and 40, Determine H. Solution. Since gcd(18,
More information4. CLASSES OF RINGS 4.1. Classes of Rings class operator A-closed Example 1: product Example 2:
4. CLASSES OF RINGS 4.1. Classes of Rings Normally we associate, with any property, a set of objects that satisfy that property. But problems can arise when we allow sets to be elements of larger sets
More informationGeometric Transformations
Geometric Transformations Definitions Def: f is a mapping (function) of a set A into a set B if for every element a of A there exists a unique element b of B that is paired with a; this pairing is denoted
More informationAbstract Algebra Cheat Sheet
Abstract Algebra Cheat Sheet 16 December 2002 By Brendan Kidwell, based on Dr. Ward Heilman s notes for his Abstract Algebra class. Notes: Where applicable, page numbers are listed in parentheses at the
More information6 Commutators and the derived series. [x,y] = xyx 1 y 1.
6 Commutators and the derived series Definition. Let G be a group, and let x,y G. The commutator of x and y is [x,y] = xyx 1 y 1. Note that [x,y] = e if and only if xy = yx (since x 1 y 1 = (yx) 1 ). Proposition
More informationMATH PROBLEMS, WITH SOLUTIONS
MATH PROBLEMS, WITH SOLUTIONS OVIDIU MUNTEANU These are free online notes that I wrote to assist students that wish to test their math skills with some problems that go beyond the usual curriculum. These
More informationLinear Algebra I. Ronald van Luijk, 2012
Linear Algebra I Ronald van Luijk, 2012 With many parts from Linear Algebra I by Michael Stoll, 2007 Contents 1. Vector spaces 3 1.1. Examples 3 1.2. Fields 4 1.3. The field of complex numbers. 6 1.4.
More informationON GALOIS REALIZATIONS OF THE 2-COVERABLE SYMMETRIC AND ALTERNATING GROUPS
ON GALOIS REALIZATIONS OF THE 2-COVERABLE SYMMETRIC AND ALTERNATING GROUPS DANIEL RABAYEV AND JACK SONN Abstract. Let f(x) be a monic polynomial in Z[x] with no rational roots but with roots in Q p for
More informationPOLYNOMIAL RINGS AND UNIQUE FACTORIZATION DOMAINS
POLYNOMIAL RINGS AND UNIQUE FACTORIZATION DOMAINS RUSS WOODROOFE 1. Unique Factorization Domains Throughout the following, we think of R as sitting inside R[x] as the constant polynomials (of degree 0).
More informationTHREE DIMENSIONAL GEOMETRY
Chapter 8 THREE DIMENSIONAL GEOMETRY 8.1 Introduction In this chapter we present a vector algebra approach to three dimensional geometry. The aim is to present standard properties of lines and planes,
More informationDistributed Coverage Verification in Sensor Networks Without Location Information Alireza Tahbaz-Salehi and Ali Jadbabaie, Senior Member, IEEE
IEEE TRANSACTIONS ON AUTOMATIC CONTROL, VOL. 55, NO. 8, AUGUST 2010 1837 Distributed Coverage Verification in Sensor Networks Without Location Information Alireza Tahbaz-Salehi and Ali Jadbabaie, Senior
More informationSurvey and remarks on Viro s definition of Khovanov homology
RIMS Kôkyûroku Bessatsu B39 (203), 009 09 Survey and remarks on Viro s definition of Khovanov homology By Noboru Ito Abstract This paper reviews and offers remarks upon Viro s definition of the Khovanov
More informationHow To Solve The Group Theory
Chapter 5 Some Basic Techniques of Group Theory 5.1 Groups Acting on Sets In this chapter we are going to analyze and classify groups, and, if possible, break down complicated groups into simpler components.
More informationDiscrete Mathematics & Mathematical Reasoning Chapter 10: Graphs
Discrete Mathematics & Mathematical Reasoning Chapter 10: Graphs Kousha Etessami U. of Edinburgh, UK Kousha Etessami (U. of Edinburgh, UK) Discrete Mathematics (Chapter 6) 1 / 13 Overview Graphs and Graph
More informationSimilarity and Diagonalization. Similar Matrices
MATH022 Linear Algebra Brief lecture notes 48 Similarity and Diagonalization Similar Matrices Let A and B be n n matrices. We say that A is similar to B if there is an invertible n n matrix P such that
More informationModule MA3411: Abstract Algebra Galois Theory Appendix Michaelmas Term 2013
Module MA3411: Abstract Algebra Galois Theory Appendix Michaelmas Term 2013 D. R. Wilkins Copyright c David R. Wilkins 1997 2013 Contents A Cyclotomic Polynomials 79 A.1 Minimum Polynomials of Roots of
More informationCOMMUTATIVITY DEGREE, ITS GENERALIZATIONS, AND CLASSIFICATION OF FINITE GROUPS
COMMUTATIVITY DEGREE, ITS GENERALIZATIONS, AND CLASSIFICATION OF FINITE GROUPS ABSTRACT RAJAT KANTI NATH DEPARTMENT OF MATHEMATICS NORTH-EASTERN HILL UNIVERSITY SHILLONG 793022, INDIA COMMUTATIVITY DEGREE,
More informationMathematical Research Letters 1, 249 255 (1994) MAPPING CLASS GROUPS ARE AUTOMATIC. Lee Mosher
Mathematical Research Letters 1, 249 255 (1994) MAPPING CLASS GROUPS ARE AUTOMATIC Lee Mosher Let S be a compact surface, possibly with the extra structure of an orientation or a finite set of distinguished
More informationON TORI TRIANGULATIONS ASSOCIATED WITH TWO-DIMENSIONAL CONTINUED FRACTIONS OF CUBIC IRRATIONALITIES.
ON TORI TRIANGULATIONS ASSOCIATED WITH TWO-DIMENSIONAL CONTINUED FRACTIONS OF CUBIC IRRATIONALITIES. O. N. KARPENKOV Introduction. A series of properties for ordinary continued fractions possesses multidimensional
More informationOnline publication date: 11 March 2010 PLEASE SCROLL DOWN FOR ARTICLE
This article was downloaded by: [Modoi, George Ciprian] On: 12 March 2010 Access details: Access Details: [subscription number 919828804] Publisher Taylor & Francis Informa Ltd Registered in England and
More informationTest1. Due Friday, March 13, 2015.
1 Abstract Algebra Professor M. Zuker Test1. Due Friday, March 13, 2015. 1. Euclidean algorithm and related. (a) Suppose that a and b are two positive integers and that gcd(a, b) = d. Find all solutions
More informationCHAPTER SIX IRREDUCIBILITY AND FACTORIZATION 1. BASIC DIVISIBILITY THEORY
January 10, 2010 CHAPTER SIX IRREDUCIBILITY AND FACTORIZATION 1. BASIC DIVISIBILITY THEORY The set of polynomials over a field F is a ring, whose structure shares with the ring of integers many characteristics.
More informationAn Introduction to Braid Theory
An Introduction to Braid Theory Maurice Chiodo November 4, 2005 Abstract In this paper we present an introduction to the theory of braids. We lay down some clear definitions of a braid, and proceed to
More informationThe Clar Structure of Fullerenes
The Clar Structure of Fullerenes Liz Hartung Massachusetts College of Liberal Arts June 12, 2013 Liz Hartung (Massachusetts College of Liberal Arts) The Clar Structure of Fullerenes June 12, 2013 1 / 25
More informationMATRIX ALGEBRA AND SYSTEMS OF EQUATIONS
MATRIX ALGEBRA AND SYSTEMS OF EQUATIONS Systems of Equations and Matrices Representation of a linear system The general system of m equations in n unknowns can be written a x + a 2 x 2 + + a n x n b a
More informationIntroduction to Topology
Introduction to Topology Tomoo Matsumura November 30, 2010 Contents 1 Topological spaces 3 1.1 Basis of a Topology......................................... 3 1.2 Comparing Topologies.......................................
More informationTuring Degrees and Definability of the Jump. Theodore A. Slaman. University of California, Berkeley. CJuly, 2005
Turing Degrees and Definability of the Jump Theodore A. Slaman University of California, Berkeley CJuly, 2005 Outline Lecture 1 Forcing in arithmetic Coding and decoding theorems Automorphisms of countable
More informationNotes on Algebraic Structures. Peter J. Cameron
Notes on Algebraic Structures Peter J. Cameron ii Preface These are the notes of the second-year course Algebraic Structures I at Queen Mary, University of London, as I taught it in the second semester
More informationIRREDUCIBLE OPERATOR SEMIGROUPS SUCH THAT AB AND BA ARE PROPORTIONAL. 1. Introduction
IRREDUCIBLE OPERATOR SEMIGROUPS SUCH THAT AB AND BA ARE PROPORTIONAL R. DRNOVŠEK, T. KOŠIR Dedicated to Prof. Heydar Radjavi on the occasion of his seventieth birthday. Abstract. Let S be an irreducible
More informationNOTES ON GROUP THEORY
NOTES ON GROUP THEORY Abstract. These are the notes prepared for the course MTH 751 to be offered to the PhD students at IIT Kanpur. Contents 1. Binary Structure 2 2. Group Structure 5 3. Group Actions
More informationGeometry and Topology from Point Cloud Data
Geometry and Topology from Point Cloud Data Tamal K. Dey Department of Computer Science and Engineering The Ohio State University Dey (2011) Geometry and Topology from Point Cloud Data WALCOM 11 1 / 51
More informationBOUNDED COHOMOLOGY CHARACTERIZES HYPERBOLIC GROUPS
BOUNDED COHOMOLOGY CHARACTERIZES HYPERBOLIC GROUPS by IGOR MINEYEV (University of South Alabama, Department of Mathematics & Statistics, ILB 35, Mobile, AL 36688, USA) [Received June 00] Abstract A finitely
More informationCOMBINATORIAL PROPERTIES OF THE HIGMAN-SIMS GRAPH. 1. Introduction
COMBINATORIAL PROPERTIES OF THE HIGMAN-SIMS GRAPH ZACHARY ABEL 1. Introduction In this survey we discuss properties of the Higman-Sims graph, which has 100 vertices, 1100 edges, and is 22 regular. In fact
More informationWORKSHOP ON TOPOLOGY AND ABSTRACT ALGEBRA FOR BIOMEDICINE
WORKSHOP ON TOPOLOGY AND ABSTRACT ALGEBRA FOR BIOMEDICINE ERIC K. NEUMANN Foundation Medicine, Cambridge, MA 02139, USA Email: eneumann@foundationmedicine.com SVETLANA LOCKWOOD School of Electrical Engineering
More informationMA651 Topology. Lecture 6. Separation Axioms.
MA651 Topology. Lecture 6. Separation Axioms. This text is based on the following books: Fundamental concepts of topology by Peter O Neil Elements of Mathematics: General Topology by Nicolas Bourbaki Counterexamples
More informationit is easy to see that α = a
21. Polynomial rings Let us now turn out attention to determining the prime elements of a polynomial ring, where the coefficient ring is a field. We already know that such a polynomial ring is a UF. Therefore
More informationGROUP ACTIONS KEITH CONRAD
GROUP ACTIONS KEITH CONRAD 1. Introduction The symmetric groups S n, alternating groups A n, and (for n 3) dihedral groups D n behave, by their very definition, as permutations on certain sets. The groups
More informationIdeal Class Group and Units
Chapter 4 Ideal Class Group and Units We are now interested in understanding two aspects of ring of integers of number fields: how principal they are (that is, what is the proportion of principal ideals
More informationState of Stress at Point
State of Stress at Point Einstein Notation The basic idea of Einstein notation is that a covector and a vector can form a scalar: This is typically written as an explicit sum: According to this convention,
More informationF. ABTAHI and M. ZARRIN. (Communicated by J. Goldstein)
Journal of Algerian Mathematical Society Vol. 1, pp. 1 6 1 CONCERNING THE l p -CONJECTURE FOR DISCRETE SEMIGROUPS F. ABTAHI and M. ZARRIN (Communicated by J. Goldstein) Abstract. For 2 < p
More informationFixed Point Theory. With 14 Illustrations. %1 Springer
Andrzej Granas James Dugundji Fixed Point Theory With 14 Illustrations %1 Springer Contents Preface vii 0. Introduction 1 1. Fixed Point Spaces 1 2. Forming New Fixed Point Spaces from Old 3 3. Topological
More informationSplit Nonthreshold Laplacian Integral Graphs
Split Nonthreshold Laplacian Integral Graphs Stephen Kirkland University of Regina, Canada kirkland@math.uregina.ca Maria Aguieiras Alvarez de Freitas Federal University of Rio de Janeiro, Brazil maguieiras@im.ufrj.br
More informationFactoring Polynomials
UNIT 11 Factoring Polynomials You can use polynomials to describe framing for art. 396 Unit 11 factoring polynomials A polynomial is an expression that has variables that represent numbers. A number can
More informationFUNCTIONAL ANALYSIS LECTURE NOTES: QUOTIENT SPACES
FUNCTIONAL ANALYSIS LECTURE NOTES: QUOTIENT SPACES CHRISTOPHER HEIL 1. Cosets and the Quotient Space Any vector space is an abelian group under the operation of vector addition. So, if you are have studied
More informationMATH 4330/5330, Fourier Analysis Section 11, The Discrete Fourier Transform
MATH 433/533, Fourier Analysis Section 11, The Discrete Fourier Transform Now, instead of considering functions defined on a continuous domain, like the interval [, 1) or the whole real line R, we wish
More informationSets of Fibre Homotopy Classes and Twisted Order Parameter Spaces
Communications in Mathematical Physics Manuscript-Nr. (will be inserted by hand later) Sets of Fibre Homotopy Classes and Twisted Order Parameter Spaces Stefan Bechtluft-Sachs, Marco Hien Naturwissenschaftliche
More information