Algebra and topology of right-angled Artin groups
|
|
- Jeffry Ward
- 5 years ago
- Views:
Transcription
1 Algebra and topology of right-angled Artin groups Alex Suciu Northeastern University Boston, Massachusetts (visiting the University of Warwick) Algebra Seminar University of Leeds October 19, 2009 Alex Suciu (Northeastern University) Right-angled Artin groups University of Leeds, Oct / 31
2 Outline 1 Artin groups The braid groups Serre s realization problem Artin groups associated to labeled graphs Serre s problem for Artin groups Right-angled Artin groups 2 Toric complexes and right-angled Artin groups Partial products of spaces Toric complexes Associated graded Lie algebra Holonomy Lie algebra Chen Lie algebra 3 Resonance varieties The resonance varieties of a space Resonance of toric complexes Resonance of smooth, quasi-projective varieties Serre s problem for right-angled Artin groups revisited Alex Suciu (Northeastern University) Right-angled Artin groups University of Leeds, Oct / 31
3 Artin groups The braid groups The braid group Definition (E. Artin 1926/1947) σ i σ i+1 σ i = σ i+1 σ i σ i+1 1 i n 2 B n = σ 1,..., σ n 1 σ i σ j = σ j σ i i j > 1 Fits into exact sequence 1 P n B n π S n 1, where S n is the symmetric group, π sends a braid to the corresponding permutation, and P n is the group of pure" braids. Alex Suciu (Northeastern University) Right-angled Artin groups University of Leeds, Oct / 31
4 Artin groups Serre s realization problem Serre s realization problem Problem Which finitely presented groups G are (quasi-) projective, i.e., can be realized as G = π 1 (M), with M a connected, smooth, complex (quasi-) projective variety? Theorem (J.-P. Serre 1958) All finite groups are projective. Alex Suciu (Northeastern University) Right-angled Artin groups University of Leeds, Oct / 31
5 Artin groups Serre s realization problem Theorem (Fox Neuwirth 1962) Both P n and B n are quasi-projective groups. P n = π 1 (F(C, n)), where F(C, n) = C n \ {z i = z j } is the configuration space of n ordered points in C, or, the complement of the braid arrangement. B n = π 1 (C(C, n)), where C(C, n) = F(C, n)/s n = C n \ { n = 0} is the configuration space of n unordered points in C, or, the complement of the discriminant hypersurface. Remark As we shall see later, neither P n nor B n is a projective group. Alex Suciu (Northeastern University) Right-angled Artin groups University of Leeds, Oct / 31
6 Artin groups Artin groups associated to labeled graphs Artin groups Let Γ = (V, E) be a finite, simple graph, and l: E Z 2 an edge-labeling. The associated Artin group: G Γ,l = v V } vwv {{ } = wvw }{{ }, for e = {v, w} E. l(e) l(e) E.g.: (Γ, l) Dynkin diagram of type A n 1 G Γ,l = B n The corresponding Coxeter group, W Γ,l = G Γ,l / v 2 = 1 v V fits into exact sequence 1 P Γ,l G π Γ,l W Γ,l 1. Alex Suciu (Northeastern University) Right-angled Artin groups University of Leeds, Oct / 31
7 Artin groups Serre s problem for Artin groups Serre s problem for Artin groups Theorem (Brieskorn 1971) If W Γ,l is finite, then G Γ,l is quasi-projective. Idea: let A Γ,l = reflection arrangement of type W Γ,l (over C) X Γ,l = C n \ H A Γ,l H, where n = A Γ,l P Γ,l = π 1 (X Γ,l ) then: G Γ,l = π 1 (X Γ,l /W Γ,l ) = π 1 (C n \ {δ Γ,l = 0}) Theorem (Kapovich Millson 1998) There exist infinitely many (Γ, l) such that G Γ,l is not quasi-projective. Alex Suciu (Northeastern University) Right-angled Artin groups University of Leeds, Oct / 31
8 Artin groups Right-angled Artin groups Right-angled Artin groups Important particular case: l(e) = 2, for all e E. Simply write: G Γ = v V vw = wv if {v, w} E. Γ = K n (discrete graph) G Γ = F n Γ = K n (complete graph) G Γ = Z n Γ = Γ Γ G Γ = G Γ G Γ Γ = Γ Γ G Γ = G Γ G Γ Theorem (Kim Makar-Limanov Neggers Roush 80/Droms 87) Γ = Γ G Γ = GΓ Alex Suciu (Northeastern University) Right-angled Artin groups University of Leeds, Oct / 31
9 Artin groups Right-angled Artin groups Serre s problem for right-angled Artin groups Theorem (Dimca Papadima S. 2009) The following are equivalent: 1 G Γ is a quasi-projective group 2 Γ = K n1 K nr 3 G Γ = F n1 F nr 1 G Γ is a projective group 2 Γ = K 2r 3 G Γ = Z 2r Alex Suciu (Northeastern University) Right-angled Artin groups University of Leeds, Oct / 31
10 Toric complexes and right-angled Artin groups Partial products of spaces Partial product construction Input: L, a simplicial complex on [n] = {1,..., n}. (X, A), a pair of topological spaces, A. Output: (X, A) L = (X, A) σ X n σ L where (X, A) σ = {x X n x i A if i / σ}. Interpolates between A n and X n. Converts simplicial joins to direct products: (X, A) K L = (X, A) K (X, A) L. Alex Suciu (Northeastern University) Right-angled Artin groups University of Leeds, Oct / 31
11 Toric complexes and right-angled Artin groups Toric complexes Toric complexes Definition The toric complex associated to L is the space T L = (S 1, ) L. In other words: Circle S 1 = e 0 e 1, with basepoint = e 0. Torus T n = (S 1 ) n, with product cell structure: (k 1)-simplex σ = {i 1,..., i k } k-cell e σ = ei 1 1 ei 1 k T L = σ L eσ. Examples: T = T n points = n S 1 T n 1 = (n 1)-skeleton of T n T n 1 = T n Alex Suciu (Northeastern University) Right-angled Artin groups University of Leeds, Oct / 31
12 Toric complexes and right-angled Artin groups Toric complexes k-cells in T L (k 1)-simplices in L. C CW (T L ) is a subcomplex of C CW (T n ); thus, all k = 0, and H k (T L, Z) = C simplicial k 1 (L, Z) = Z # (k 1)-simplices of L. H (T L, k) is the exterior Stanley-Reisner ring k L = E/J L, where E = exterior algebra (over k) on generators v1,..., v n in degree 1; J L = ideal generated by all monomials vi 1 vi k corresponding to simplices {i 1,..., i k } / L. Clearly, π 1 (T L ) = G Γ, where Γ = L (1). T L is formal, and so G Γ is 1-formal. (Notbohm Ray 2005) In fact, G Γ,l is 1-formal. (Kapovich Millson) Alex Suciu (Northeastern University) Right-angled Artin groups University of Leeds, Oct / 31
13 Toric complexes and right-angled Artin groups Toric complexes K (G Γ, 1) = T Γ, where Γ is the flag complex of Γ. (Davis Charney 1995, Meier VanWyk 1995) Hence, H (G Γ, k) = k (v 1,..., v n )/J Γ, where J Γ = ideal(vi vj {v i, v j } / E(Γ)) Since J Γ is a quadratic monomial ideal, A = E/J Γ is a Koszul algebra (Fröberg 1975), i.e., Tor A i (k, k) j = 0, for all i j. Alex Suciu (Northeastern University) Right-angled Artin groups University of Leeds, Oct / 31
14 Toric complexes and right-angled Artin groups Associated graded Lie algebra Associated graded Lie algebra Let G be a finitely-generated group. Define: LCS series: G = G 1 G 2 G k, where G k+1 = [G k, G] LCS quotients: gr k G = G k /G k+1 (f.g. abelian groups) LCS ranks: φ k (G) = rank(gr k G) Associated graded Lie algebra: gr(g) = k 1 gr k (G), with Lie bracket [, ]: gr k gr l gr k+l induced by group commutator. Alex Suciu (Northeastern University) Right-angled Artin groups University of Leeds, Oct / 31
15 Toric complexes and right-angled Artin groups Associated graded Lie algebra Example (Witt, Magnus) Let G = F n (free group of rank n). Then gr G = Lie n (free Lie algebra of rank n), with LCS ranks given by Explicitly: φ k (F n ) = 1 k (1 t k ) φ k = 1 nt. k=1 d k µ(d)nk/d, where µ is Möbius function. Example (Kohno 1985) Let G = P n. Then: (1 t k ) φ k = (1 t) (1 (n 1)t) k=1 In other words, φ k (P n ) = φ k (F 1 F n 1 ). Alex Suciu (Northeastern University) Right-angled Artin groups University of Leeds, Oct / 31
16 Toric complexes and right-angled Artin groups Holonomy Lie algebra Holonomy Lie algebra Definition (Chen 1977, Markl Papadima 1992) Let G be a finitely generated group, with H 1 = H 1 (G, Z) torsion-free. The holonomy Lie algebra of G is the quadratic, graded Lie algebra h G = Lie(H 1 )/ideal(im( )), where : H 2 (G, Z) H 1 H 1 = Lie 2 (H 1 ) is the comultiplication map. Let G = π 1 (X) and A = H (X, Q). (Löfwall 1986) U(h G Q) = k 1 Extk A (Q, Q) k. There is a canonical epimorphism h G gr(g). (Sullivan 1977) If G is 1-formal, then h G Q gr(g) Q. Example G = F n, then clearly h G = Lie n, and so h G = gr(g). Alex Suciu (Northeastern University) Right-angled Artin groups University of Leeds, Oct / 31
17 Toric complexes and right-angled Artin groups Holonomy Lie algebra Let Γ = (V, E) graph, and P Γ (t) = k 0 f k(γ)t k its clique polynomial. Theorem (Duchamp Krob 1992, Papadima S. 2006) For G = G Γ : 1 gr(g) = h G. 2 Graded pieces are torsion-free, with ranks given by Idea of proof: (1 t k ) φ k = P Γ ( t). k=1 1 A = k V /J Γ h G k = L Γ := Lie(V)/([v, w] = 0 if {v, w} E). 2 Shelton Yuzvinsky: U(L Γ ) = A! (Koszul dual). 3 Koszul duality: Hilb(A!, t) Hilb(A, t) = 1. 4 Hilb(h G k, t) independent of k h G torsion-free. 5 But h G gr(g) is iso over Q (by 1-formality) iso over Z. 6 LCS formula follows from (3) and PBW. Alex Suciu (Northeastern University) Right-angled Artin groups University of Leeds, Oct / 31
18 Toric complexes and right-angled Artin groups Chen Lie algebra Chen Lie algebras Definition (Chen 1951) The Chen Lie algebra of a finitely generated group G is gr(g/g ), i.e., the assoc. graded Lie algebra of its maximal metabelian quotient. Write θ k (G) = rank gr k (G/G ) for the Chen ranks. Facts: gr(g) gr(g/g ), and so φ k (G) θ k (G), with equality for k 3. The map h G gr(g) induces epimorphism h G /h G gr(g/g ). (P. S. 2004) If G is 1-formal, then h G /h G Q gr(g/g ) Q. Alex Suciu (Northeastern University) Right-angled Artin groups University of Leeds, Oct / 31
19 Toric complexes and right-angled Artin groups Chen Lie algebra Example (Chen 1951) gr(f n /F n ) is torsion-free, with ranks θ 1 = n, and ( ) n + k 2 θ k = (k 1), for k 2. k Example (Cohen S. 1995) gr(p n /P n ) is torsion-free, with ranks θ 1 = ( ) n 2, θ2 = ( n 3), and ( ) n + 1 θ k = (k 1), for k 3. 4 In particular, θ k (P n ) θ k (F 1 F n 1 ), for n 4 and k 4. Alex Suciu (Northeastern University) Right-angled Artin groups University of Leeds, Oct / 31
20 Toric complexes and right-angled Artin groups Chen Lie algebra The Chen Lie algebra of a RAAG Theorem (P. S. 2006) For G = G Γ : 1 gr(g/g ) = h G /h G. 2 Graded pieces are torsion-free, with ranks given by ( t θ k t k = Q Γ 1 t k=2 ), where Q Γ (t) = j 2 c j(γ)t j is the cut polynomial" of Γ, with c j (Γ) = W V: W =j b 0 (Γ W ). Alex Suciu (Northeastern University) Right-angled Artin groups University of Leeds, Oct / 31
21 Idea of proof: Toric complexes and right-angled Artin groups Chen Lie algebra 1 Write A := H (G, k) = E/J Γ, where E = k (v 1,..., v n ). 2 Write h = h G k. 3 By Fröberg and Löfwall (2002) ( h /h ) k = Tor E k 1 (A, k) k, for k 2 4 By Aramova Herzog Hibi & Aramova Avramov Herzog (97-99): dim k Tor E k 1 (E/J Γ, k) k = ( ) t i+1 dim k Tor S i (S/I Γ, k) i+1, 1 t k 2 i 1 where S = k[x 1,..., x n ] and I Γ = ideal x i x j {v i, v j } / E. 5 By Hochster (1977): dim k Tor S i (S/I Γ, k) i+1 = dim k H0 (Γ W, k) = c i+1 (Γ). W V: W =i+1 6 The answer is independent of k h G /h G is torsion-free. 7 Using formality of G Γ, together with h G /h G Q gr(g/g ) Q ends the proof. Alex Suciu (Northeastern University) Right-angled Artin groups University of Leeds, Oct / 31
22 Toric complexes and right-angled Artin groups Chen Lie algebra Example Let Γ be a pentagon, and Γ a square with an edge attached to a vertex. Then: P Γ = P Γ = 1 5t + 5t 2, and so φ k (G Γ ) = φ k (G Γ ), for all k 1. Q Γ = 5t 2 + 5t 3 but Q Γ = 5t 2 + 5t 3 + t 4, and so θ k (G Γ ) θ k (G Γ ), for k 4. Alex Suciu (Northeastern University) Right-angled Artin groups University of Leeds, Oct / 31
23 Resonance varieties The resonance varieties of a space Resonance varieties Let X be a connected CW-complex with finite k-skeleton (k 1). Let k be a field; if char k = 2, assume H 1 (X, Z) has no 2-torsion. Let A = H (X, k). Then: a A 1 a 2 = 0. Thus, get cochain complex (A, a): A 0 a A 1 a A 2 Definition (Falk 1997, Matei S. 2000) The resonance varieties of X (over k) are the algebraic sets R i d (X, k) = {a A1 dim k H i (A, a) d}, defined for all integers 0 i k and d > 0. R i d are homogeneous subvarieties of A1 = H 1 (X, k) R i 1 Ri 2 Ri b i +1 =, where b i = b i (X, k). R 1 d (X, k) depends only on G = π 1(X), so denote it by R d (G, k). Alex Suciu (Northeastern University) Right-angled Artin groups University of Leeds, Oct / 31
24 Resonance varieties Resonance of toric complexes Resonance of toric complexes Recall A = H (T L, k) is the exterior Stanley-Reisner ring of L. Identify A 1 = k V the k-vector space with basis {v v V}. Theorem (Papadima S. 2009) R i d (T L, k) = W V P σ L dim k Hi 1 σ e (lk LW (σ),k) d V\W k W, where L W is the subcomplex induced by L on W, and lk K (σ) is the link of a simplex σ in a subcomplex K L. In particular: R 1 (G Γ, k) = W V Γ W disconnected k W. Alex Suciu (Northeastern University) Right-angled Artin groups University of Leeds, Oct / 31
25 Resonance varieties Resonance of toric complexes Example Let Γ and Γ be the two graphs above. Both have P(t) = 1 + 6t + 9t 2 + 4t 3, and Q(t) = t 2 (6 + 8t + 3t 2 ). Thus, G Γ and G Γ have the same LCS and Chen ranks. Each resonance variety has 3 components, of codimension 2: R 1 (G Γ, k) = k 23 k 25 k 35, R 1 (G Γ, k) = k 15 k 25 k 26. Yet the two varieties are not isomorphic, since dim(k 23 k 25 k 35 ) = 3, but dim(k 15 k 25 k 26 ) = 2. Alex Suciu (Northeastern University) Right-angled Artin groups University of Leeds, Oct / 31
26 Resonance varieties Resonance of smooth, quasi-projective varieties Projective varieties Let M be a connected, smooth, complex projective variety. Then: 1 H (M, Z) admits a Hodge structure 2 Hence, the odd Betti numbers of M are even 3 M is formal (Deligne Griffiths Morgan Sullivan 1975) This puts strong restrictions on G = π 1 (M): 1 b 1 (G) is even 2 G is 1-formal, i.e., its Malcev Lie algebra m(g) is quadratic 3 G cannot split non-trivially as a free product (Gromov 1989) In particular, B n is not a projective group, since b 1 (B n ) = 1. Alex Suciu (Northeastern University) Right-angled Artin groups University of Leeds, Oct / 31
27 Resonance varieties Resonance of smooth, quasi-projective varieties Quasi-projective varieties Let X be a connected, smooth, quasi-projective variety. Then: H (X, Z) has a mixed Hodge structure (Deligne ) X = CP n \ {hyperplane arrangement} X is formal (Brieskorn 1973) W 1 (H 1 (X, C)) = 0 π 1 (X) is 1-formal X = CP n \ {hypersurface} π 1 (X) is 1-formal (Morgan 1978) (Kohno 1983) Alex Suciu (Northeastern University) Right-angled Artin groups University of Leeds, Oct / 31
28 Resonance varieties Resonance of smooth, quasi-projective varieties A structure theorem Theorem (D. P. S. 2009) Let X be a smooth, quasi-projective variety, and G = π 1 (X). Let {L α } α be the non-zero irred components of R 1 (G). If G is 1-formal, then 1 Each L α is a p-isotropic linear subspace of H 1 (G, C), with dim L α 2p + 2, for some p = p(α) {0, 1}. 2 If α β, then L α L β = {0}. 3 R d (G) = {0} α L α, where the union is over all α for which dim L α > d + p(α). Furthermore, 4 If X is compact, then G is 1-formal, and each L α is 1-isotropic. 5 If W 1 (H 1 (X, C)) = 0, then G is 1-formal, and each L α is 0-isotropic. Alex Suciu (Northeastern University) Right-angled Artin groups University of Leeds, Oct / 31
29 Resonance varieties Resonance of smooth, quasi-projective varieties Proof uses two basic ingredients: A structure theorem for Vd i (X, C) the jump loci for cohomology with coefficients in rank 1 local systems on a quasi-projective variety X (Arapura 1997). A tangent cone theorem", equating TC 1 (Vd 1(G, C)) with R1 d (G, C), for G a 1-formal group. Alex Suciu (Northeastern University) Right-angled Artin groups University of Leeds, Oct / 31
30 Resonance varieties Serre s problem for right-angled Artin groups revisited Serre s problem for RAAGs revisited Using this theorem, together with the computation of R 1 (G Γ, C), the characterization of those graphs Γ for which G Γ can be realized as a (quasi-) projective fundamental group follows. Example Let Γ be the graph above. The maximal disconnected subgraphs are Γ {134} and Γ {124}. Thus: R 1 (G Γ, C) = C {134} C {124}. But C {134} C {124} = C {14}, which is a non-zero subspace. But recall G Γ is 1-formal. Thus, G Γ is not a quasi-projective group. Alex Suciu (Northeastern University) Right-angled Artin groups University of Leeds, Oct / 31
31 Resonance varieties Serre s problem for right-angled Artin groups revisited References A. Dimca, S. Papadima, A. Suciu, Topology and geometry of cohomology jump loci, Duke Math. Journal 148 (2009), no. 3, S. Papadima, A. Suciu, Algebraic invariants for right-angled Artin groups, Math. Annalen 334 (2006), no. 3, , Toric complexes and Artin kernels, Advances in Math. 220 (2009), no. 2, Alex Suciu (Northeastern University) Right-angled Artin groups University of Leeds, Oct / 31
Partial products of circles
Partial products of circles Alex Suciu Northeastern University Boston, Massachusetts Algebra and Geometry Seminar Vrije University Amsterdam October 13, 2009 Alex Suciu (Northeastern University) Partial
More informationFUNDAMENTAL GROUPS IN ALGEBRAIC GEOMETRY. Alex Suciu AND THREE-DIMENSIONAL TOPOLOGY. Colloquium University of Fribourg June 7, 2016
FUNDAMENTAL GROUPS IN ALGEBRAIC GEOMETRY AND THREE-DIMENSIONAL TOPOLOGY Alex Suciu Northeastern University Colloquium University of Fribourg June 7, 2016 ALEX SUCIU (NORTHEASTERN) FUNDAMENTAL GROUPS IN
More informationPROPAGATION OF RESONANCE. Alex Suciu. Northeastern University. Joint work with Graham Denham and Sergey Yuzvinsky
COMBINATORIAL COVERS, ABELIAN DUALITY, AND PROPAGATION OF RESONANCE Alex Suciu Northeastern University Joint work with Graham Denham and Sergey Yuzvinsky Algebra, Topology and Combinatorics Seminar University
More informationLower central series, free resolutions, and homotopy Lie algebras of arrangements Alex Suciu
Lower central series, free resolutions, and homotopy Lie algebras of arrangements Alex Suciu Northeastern University www.math.neu.edu/~suciu NSF-CBMS Regional Research Conference on Arrangements and Mathematical
More informationBetti numbers of abelian covers
Betti numbers of abelian covers Alex Suciu Northeastern University Geometry and Topology Seminar University of Wisconsin May 6, 2011 Alex Suciu (Northeastern University) Betti numbers of abelian covers
More informationALGEBRAIC MODELS, DUALITY, AND RESONANCE. Alex Suciu. Topology Seminar. MIT March 5, Northeastern University
ALGEBRAIC MODELS, DUALITY, AND RESONANCE Alex Suciu Northeastern University Topology Seminar MIT March 5, 2018 ALEX SUCIU (NORTHEASTERN) MODELS, DUALITY, AND RESONANCE MIT TOPOLOGY SEMINAR 1 / 24 DUALITY
More informationResonance varieties and Dwyer Fried invariants
Resonance varieties and Dwyer Fried invariants Alexander I. Suciu Abstract. The Dwyer Fried invariants of a finite cell complex X are the subsets Ω i r (X) of the Grassmannian of r-planes in H 1 (X, Q)
More informationQUASI-KÄHLER BESTVINA-BRADY GROUPS
J. ALGEBRAIC GEOMETRY 00 (XXXX) 000 000 S 1056-3911(XX)0000-0 QUASI-KÄHLER BESTVINA-BRADY GROUPS ALEXANDRU DIMCA, STEFAN PAPADIMA 1, AND ALEXANDER I. SUCIU 2 Abstract A finite simple graph Γ determines
More informationOn the topology of matrix configuration spaces
On the topology of matrix configuration spaces Daniel C. Cohen Department of Mathematics Louisiana State University Daniel C. Cohen (LSU) Matrix configuration spaces Summer 2013 1 Configuration spaces
More informationFUNDAMENTAL GROUPS. Alex Suciu. Northeastern University. Joint work with Thomas Koberda (U. Virginia) arxiv:
RESIDUAL FINITENESS PROPERTIES OF FUNDAMENTAL GROUPS Alex Suciu Northeastern University Joint work with Thomas Koberda (U. Virginia) arxiv:1604.02010 Number Theory and Algebraic Geometry Seminar Katholieke
More informationThe rational cohomology of real quasi-toric manifolds
The rational cohomology of real quasi-toric manifolds Alex Suciu Northeastern University Joint work with Alvise Trevisan (VU Amsterdam) Toric Methods in Homotopy Theory Queen s University Belfast July
More informationPOLYHEDRAL PRODUCTS. Alex Suciu. Northeastern University
REPRESENTATION VARIETIES AND POLYHEDRAL PRODUCTS Alex Suciu Northeastern University Special Session Representation Spaces and Toric Topology AMS Spring Eastern Sectional Meeting Hunter College, New York
More informationHomotopy types of the complements of hyperplane arrangements, local system homology and iterated integrals
Homotopy types of the complements of hyperplane arrangements, local system homology and iterated integrals Toshitake Kohno The University of Tokyo August 2009 Plan Part 1 : Homotopy types of the complements
More informationPOLYHEDRAL PRODUCTS, TORIC MANIFOLDS, AND. Alex Suciu TWISTED COHOMOLOGY. Princeton Rider workshop Homotopy theory and toric spaces.
POLYHEDRAL PRODUCTS, TORIC MANIFOLDS, AND TWISTED COHOMOLOGY Alex Suciu Northeastern University Princeton Rider workshop Homotopy theory and toric spaces February 23, 2012 ALEX SUCIU (NORTHEASTERN) POLYHEDRAL
More informationMilnor Fibers of Line Arrangements
Milnor Fibers of Line Arrangements Alexandru Dimca Université de Nice, France Lib60ber Topology of Algebraic Varieties Jaca, Aragón June 25, 2009 Outline Outline 1 Anatoly and me, the true story... 2 Definitions,
More informationMath 797W Homework 4
Math 797W Homework 4 Paul Hacking December 5, 2016 We work over an algebraically closed field k. (1) Let F be a sheaf of abelian groups on a topological space X, and p X a point. Recall the definition
More informationarxiv: v2 [math.at] 17 Sep 2009
ALGEBRAIC MONODROMY AND OBSTRUCTIONS TO FORMALITY arxiv:0901.0105v2 [math.at] 17 Sep 2009 STEFAN PAPADIMA 1 AND ALEXANDER I. SUCIU 2 Abstract. Given a fibration over the circle, we relate the eigenspace
More informationTOPOLOGY OF LINE ARRANGEMENTS. Alex Suciu. Northeastern University. Workshop on Configuration Spaces Il Palazzone di Cortona September 1, 2014
TOPOLOGY OF LINE ARRANGEMENTS Alex Suciu Northeastern University Workshop on Configuration Spaces Il Palazzone di Cortona September 1, 2014 ALEX SUCIU (NORTHEASTERN) TOPOLOGY OF LINE ARRANGEMENTS CORTONA,
More informationCoxeter Groups and Artin Groups
Chapter 1 Coxeter Groups and Artin Groups 1.1 Artin Groups Let M be a Coxeter matrix with index set S. defined by M is given by the presentation: A M := s S sts }{{ } = tst }{{ } m s,t factors m s,t The
More informationGeneralized Alexander duality and applications. Osaka Journal of Mathematics. 38(2) P.469-P.485
Title Generalized Alexander duality and applications Author(s) Romer, Tim Citation Osaka Journal of Mathematics. 38(2) P.469-P.485 Issue Date 2001-06 Text Version publisher URL https://doi.org/10.18910/4757
More informationHodge theory for combinatorial geometries
Hodge theory for combinatorial geometries June Huh with Karim Adiprasito and Eric Katz June Huh 1 / 48 Three fundamental ideas: June Huh 2 / 48 Three fundamental ideas: The idea of Bernd Sturmfels that
More informationTOPOLOGY HYPERPLANE ARRANGEMENTS. Alex Suciu. Northeastern University.
TOPOLOGY OF HYPERPLANE ARRANGEMENTS Alex Suciu Northeastern University www.math.neu.edu/~suciu A.M.S. Fall Eastern Section Meeting Columbia University, New York, NY November 5, 2000 1 Hyperplane arrangements
More informationGeneralized Moment-Angle Complexes, Lecture 3
Generalized Moment-Angle Complexes, Lecture 3 Fred Cohen 1-5 June 2010 joint work with Tony Bahri, Martin Bendersky, and Sam Gitler Outline of the lecture: This lecture addresses the following points.
More informationCohomology jump loci of local systems
Cohomology jump loci of local systems Botong Wang Joint work with Nero Budur University of Notre Dame June 28 2013 Introduction Given a topological space X, we can associate some homotopy invariants to
More informationA short introduction to arrangements of hyperplanes
A short introduction to arrangements of hyperplanes survey Sergey Yuzvinsky University of Oregon Pisa, May 2010 Setup and notation By a hyperplane arrangement we understand the set A of several hyperplanes
More informationModel categories and homotopy colimits in toric topology
Model categories and homotopy colimits in toric topology Taras Panov Moscow State University joint work with Nigel Ray 1 1. Motivations. Object of study of toric topology : torus actions on manifolds or
More informationFREE RESOLUTION OF POWERS OF MONOMIAL IDEALS AND GOLOD RINGS
FREE RESOLUTION OF POWERS OF MONOMIAL IDEALS AND GOLOD RINGS N. ALTAFI, N. NEMATI, S. A. SEYED FAKHARI, AND S. YASSEMI Abstract. Let S = K[x 1,..., x n ] be the polynomial ring over a field K. In this
More informationLecture 1. Toric Varieties: Basics
Lecture 1. Toric Varieties: Basics Taras Panov Lomonosov Moscow State University Summer School Current Developments in Geometry Novosibirsk, 27 August1 September 2018 Taras Panov (Moscow University) Lecture
More informationAnnihilators of Orlik Solomon Relations
Advances in Applied Mathematics 28, 231 249 (2002) doi:10.1006/aama.2001.0779, available online at http://www.idealibrary.com on Annihilators of Orlik Solomon Relations Graham Denham 1 and Sergey Yuzvinsky
More informationGeneric section of a hyperplane arrangement and twisted Hurewicz maps
arxiv:math/0605643v2 [math.gt] 26 Oct 2007 Generic section of a hyperplane arrangement and twisted Hurewicz maps Masahiko Yoshinaga Department of Mathematice, Graduate School of Science, Kobe University,
More informationABELIAN ARRANGEMENTS
ABELIAN ARRANGEMENTS by CHRISTIN BIBBY A DISSERTATION Presented to the Department of Mathematics and the Graduate School of the University of Oregon in partial fulfillment of the requirements for the degree
More informationALGEBRAIC PROPERTIES OF BIER SPHERES
LE MATEMATICHE Vol. LXVII (2012 Fasc. I, pp. 91 101 doi: 10.4418/2012.67.1.9 ALGEBRAIC PROPERTIES OF BIER SPHERES INGA HEUDTLASS - LUKAS KATTHÄN We give a classification of flag Bier spheres, as well as
More informationMathematisches Forschungsinstitut Oberwolfach. Miniworkshop: Cohomology Jumping Loci
Mathematisches Forschungsinstitut Oberwolfach Report No. 11/2002 Miniworkshop: Cohomology Jumping Loci March 3rd March 9th, 2002 1. Overview This Mini-Workshop was organized by A. Suciu (Boston) and S.
More informationThe surprising thing about Theorem 1.1 is that Artin groups look very similar to the fundamental groups of smooth complex quasi-projective varieties.
On representation varieties of Artin groups, projective arrangements and the fundamental groups of smooth complex algebraic varieties Michael Kapovich and John J. Millson y November 17, 1997 Abstract We
More informationCombinatorics and geometry of E 7
Combinatorics and geometry of E 7 Steven Sam University of California, Berkeley September 19, 2012 1/24 Outline Macdonald representations Vinberg representations Root system Weyl group 7 points in P 2
More informationNotes on p-divisible Groups
Notes on p-divisible Groups March 24, 2006 This is a note for the talk in STAGE in MIT. The content is basically following the paper [T]. 1 Preliminaries and Notations Notation 1.1. Let R be a complete
More informationCohomology jump loci of quasi-projective varieties
Cohomology jump loci of quasi-projective varieties Botong Wang joint work with Nero Budur University of Notre Dame June 27 2013 Motivation What topological spaces are homeomorphic (or homotopy equivalent)
More informationarxiv: v2 [math.gr] 8 Jul 2012
GEOMETRIC AND HOMOLOGICAL FINITENESS IN FREE ABELIAN COVERS ALEXANDER I. SUCIU arxiv:1112.0948v2 [math.gr] 8 Jul 2012 Abstract. We describe some of the connections between the Bieri Neumann Strebel Renz
More informationHomotopy types of moment-angle complexes
Homotopy types of moment-angle complexes based on joint work with Jelena Grbic, Stephen Theriault and Jie Wu Taras Panov Lomonosov Moscow State University The 39th Symposium on Transformation Groups Tokyo
More informationH A A}. ) < k, then there are constants c t such that c t α t = 0. j=1 H i j
M ath. Res. Lett. 16 (2009), no. 1, 171 182 c International Press 2009 THE ORLIK-TERAO ALGEBRA AND 2-FORMALITY Hal Schenck and Ştefan O. Tohǎneanu Abstract. The Orlik-Solomon algebra is the cohomology
More informationFORMALITY OF THE COMPLEMENTS OF SUBSPACE ARRANGEMENTS WITH GEOMETRIC LATTICES
FORMALITY OF THE COMPLEMENTS OF SUBSPACE ARRANGEMENTS WITH GEOMETRIC LATTICES EVA MARIA FEICHTNER AND SERGEY YUZVINSKY Abstract. We show that, for an arrangement of subspaces in a complex vector space
More information7.3 Singular Homology Groups
184 CHAPTER 7. HOMOLOGY THEORY 7.3 Singular Homology Groups 7.3.1 Cycles, Boundaries and Homology Groups We can define the singular p-chains with coefficients in a field K. Furthermore, we can define the
More informationOn the isotropic subspace theorems
Bull. Math. Soc. Sci. Math. Roumanie Tome 51(99) No. 4, 2008, 307 324 On the isotropic subspace theorems by Alexandru Dimca Abstract In this paper we explore the Isotropic Subspace Theorems of Catanese
More informationMath 6510 Homework 10
2.2 Problems 9 Problem. Compute the homology group of the following 2-complexes X: a) The quotient of S 2 obtained by identifying north and south poles to a point b) S 1 (S 1 S 1 ) c) The space obtained
More informationJUMP LOCI. Alex Suciu. Northeastern University. Intensive research period on Algebraic Topology, Geometric and Combinatorial Group Theory
ALGEBRAIC MODELS AND COHOMOLOGY JUMP LOCI Alex Suciu Northeastern University Intensive research period on Algebraic Topology, Geometric and Combinatorial Group Theory Centro di Ricerca Matematica Ennio
More informationFree Loop Cohomology of Complete Flag Manifolds
June 12, 2015 Lie Groups Recall that a Lie group is a space with a group structure where inversion and group multiplication are smooth. Lie Groups Recall that a Lie group is a space with a group structure
More informationCW-complexes. Stephen A. Mitchell. November 1997
CW-complexes Stephen A. Mitchell November 1997 A CW-complex is first of all a Hausdorff space X equipped with a collection of characteristic maps φ n α : D n X. Here n ranges over the nonnegative integers,
More informationJournal of Algebra 226, (2000) doi: /jabr , available online at on. Artin Level Modules.
Journal of Algebra 226, 361 374 (2000) doi:10.1006/jabr.1999.8185, available online at http://www.idealibrary.com on Artin Level Modules Mats Boij Department of Mathematics, KTH, S 100 44 Stockholm, Sweden
More informationRIGHT-ANGLED ARTIN GROUPS AND THEIR SUBGROUPS. March 7, 2013
RIGHT-ANGLED ARTIN GROUPS AND THEIR SUBGROUPS THOMAS KOBERDA Abstract. These are notes for a course offered at Yale University in the spring semester of 2013. March 7, 2013 Contents 1. Introduction 2 1.1.
More informationConnected Sums of Simplicial Complexes
Connected Sums of Simplicial Complexes Tomoo Matsumura 1 W. Frank Moore 2 1 KAIST 2 Department of Mathematics Wake Forest University October 15, 2011 Let R,S,T be commutative rings, and let V be a T -module.
More informationLINEAR RESOLUTIONS OF QUADRATIC MONOMIAL IDEALS. 1. Introduction. Let G be a simple graph (undirected with no loops or multiple edges) on the vertex
LINEAR RESOLUTIONS OF QUADRATIC MONOMIAL IDEALS NOAM HORWITZ Abstract. We study the minimal free resolution of a quadratic monomial ideal in the case where the resolution is linear. First, we focus on
More informationMirror Reflections on Braids and the Higher Homotopy Groups of the 2-sphere
Mirror Reflections on Braids and the Higher Homotopy Groups of the 2-sphere A gift to Professor Jiang Bo Jü Jie Wu Department of Mathematics National University of Singapore www.math.nus.edu.sg/ matwujie
More informationThree Descriptions of the Cohomology of Bun G (X) (Lecture 4)
Three Descriptions of the Cohomology of Bun G (X) (Lecture 4) February 5, 2014 Let k be an algebraically closed field, let X be a algebraic curve over k (always assumed to be smooth and complete), and
More informationPseudo symmetric monomial curves
Pseudo symmetric monomial curves Mesut Şahin HACETTEPE UNIVERSITY Joint work with Nil Şahin (Bilkent University) Supported by Tubitak No: 114F094 IMNS 2016, July 4-8, 2016 Mesut Şahin (HACETTEPE UNIVERSITY)
More informationDemushkin s Theorem in Codimension One
Universität Konstanz Demushkin s Theorem in Codimension One Florian Berchtold Jürgen Hausen Konstanzer Schriften in Mathematik und Informatik Nr. 176, Juni 22 ISSN 143 3558 c Fachbereich Mathematik und
More informationarxiv:math/ v1 [math.ag] 19 Jul 1999
ARRANGEMENTS AND LOCAL SYSTEMS DANIEL C. COHEN AND PETER ORLIK arxiv:math/9907117v1 [math.ag] 19 Jul 1999 Abstract. We use stratified Morse theory to construct a complex to compute the cohomology of the
More informationCombinatorics for algebraic geometers
Combinatorics for algebraic geometers Calculations in enumerative geometry Maria Monks March 17, 214 Motivation Enumerative geometry In the late 18 s, Hermann Schubert investigated problems in what is
More informationExercises on characteristic classes
Exercises on characteristic classes April 24, 2016 1. a) Compute the Stiefel-Whitney classes of the tangent bundle of RP n. (Use the method from class for the tangent Chern classes of complex projectives
More informationPolytopes and Algebraic Geometry. Jesús A. De Loera University of California, Davis
Polytopes and Algebraic Geometry Jesús A. De Loera University of California, Davis Outline of the talk 1. Four classic results relating polytopes and algebraic geometry: (A) Toric Geometry (B) Viro s Theorem
More informationAutomorphisms of RAAGs and Partially symmetric automorphisms of free groups. Karen Vogtmann joint work with R. Charney November 30, 2007
Automorphisms of RAAGs and Partially symmetric automorphisms of free groups Karen Vogtmann joint work with R. Charney November 30, 2007 Right-angled Artin groups! = simplicial graph The right-angled Artin
More informationA manifestation of the Grothendieck-Teichmueller group in geometry
A manifestation of the Grothendieck-Teichmueller group in geometry Vasily Dolgushev Temple University Vasily Dolgushev (Temple University) GRT in geometry 1 / 14 Kontsevich s conjecture on the action of
More information1. Algebraic vector bundles. Affine Varieties
0. Brief overview Cycles and bundles are intrinsic invariants of algebraic varieties Close connections going back to Grothendieck Work with quasi-projective varieties over a field k Affine Varieties 1.
More informationarxiv: v2 [math.ac] 29 Sep 2013
FREE RESOLUTION OF POWERS OF MONOMIAL IDEALS AND GOLOD RINGS arxiv:1309.6351v2 [math.ac] 29 Sep 2013 N. ALTAFI, N. NEMATI, S. A. SEYED FAKHARI, AND S. YASSEMI Abstract. Let S = K[x 1,...,x n ] be the polynomial
More informationGorenstein rings through face rings of manifolds.
Gorenstein rings through face rings of manifolds. Isabella Novik Department of Mathematics, Box 354350 University of Washington, Seattle, WA 98195-4350, USA, novik@math.washington.edu Ed Swartz Department
More informationarxiv: v1 [math.ac] 11 Dec 2013
A KOSZUL FILTRATION FOR THE SECOND SQUAREFREE VERONESE SUBRING arxiv:1312.3076v1 [math.ac] 11 Dec 2013 TAKAYUKI HIBI, AYESHA ASLOOB QURESHI AND AKIHIRO SHIKAMA Abstract. The second squarefree Veronese
More informationExtensions of Stanley-Reisner theory: Cell complexes and be
: Cell complexes and beyond February 1, 2012 Polyhedral cell complexes Γ a bounded polyhedral complex (or more generally: a finite regular cell complex with the intersection property). Polyhedral cell
More informationPERVERSE SHEAVES ON A TRIANGULATED SPACE
PERVERSE SHEAVES ON A TRIANGULATED SPACE A. POLISHCHUK The goal of this note is to prove that the category of perverse sheaves constructible with respect to a triangulation is Koszul (i.e. equivalent to
More informationAlgebraic Topology exam
Instituto Superior Técnico Departamento de Matemática Algebraic Topology exam June 12th 2017 1. Let X be a square with the edges cyclically identified: X = [0, 1] 2 / with (a) Compute π 1 (X). (x, 0) (1,
More informationHomogeneous Coordinate Ring
Students: Kaiserslautern University Algebraic Group June 14, 2013 Outline Quotients in Algebraic Geometry 1 Quotients in Algebraic Geometry 2 3 4 Outline Quotients in Algebraic Geometry 1 Quotients in
More informationON COHERENCE OF GRAPH PRODUCTS AND COXETER GROUPS
ON COHERENCE OF GRAPH PRODUCTS AND COXETER GROUPS OLGA VARGHESE Abstract. Graph products and Coxeter groups are defined via vertex-edge-labeled graphs. We show that if the graph has a special shape, then
More informationON THE ISOMORPHISM CONJECTURE FOR GROUPS ACTING ON TREES
ON THE ISOMORPHISM CONJECTURE FOR GROUPS ACTING ON TREES S.K. ROUSHON Abstract. We study the Fibered Isomorphism conjecture of Farrell and Jones for groups acting on trees. We show that under certain conditions
More informationON THE CLASSIFICATION OF RANK 1 GROUPS OVER NON ARCHIMEDEAN LOCAL FIELDS
ON THE CLASSIFICATION OF RANK 1 GROUPS OVER NON ARCHIMEDEAN LOCAL FIELDS LISA CARBONE Abstract. We outline the classification of K rank 1 groups over non archimedean local fields K up to strict isogeny,
More informationarxiv: v1 [math.ac] 8 Jun 2010
REGULARITY OF CANONICAL AND DEFICIENCY MODULES FOR MONOMIAL IDEALS arxiv:1006.1444v1 [math.ac] 8 Jun 2010 MANOJ KUMMINI AND SATOSHI MURAI Abstract. We show that the Castelnuovo Mumford regularity of the
More informationGEOMETRY FINAL CLAY SHONKWILER
GEOMETRY FINAL CLAY SHONKWILER 1 Let X be the space obtained by adding to a 2-dimensional sphere of radius one, a line on the z-axis going from north pole to south pole. Compute the fundamental group and
More informationThe Real Grassmannian Gr(2, 4)
The Real Grassmannian Gr(2, 4) We discuss the topology of the real Grassmannian Gr(2, 4) of 2-planes in R 4 and its double cover Gr + (2, 4) by the Grassmannian of oriented 2-planes They are compact four-manifolds
More informationLOWER CENTRAL SERIES AND FREE RESOLUTIONS OF HYPERPLANE ARRANGEMENTS
TRANSACTIONS OF THE AMERICAN MATHEMATICAL SOCIETY Volume 54, Number 9, Pages 409 4 S 000-9947(0001-0 Article electronically published on May 8, 00 LOWER CENTRAL SERIES AND FREE RESOLUTIONS OF HYPERPLANE
More informationIntersections of Leray Complexes and Regularity of Monomial Ideals
Intersections of Leray Complexes and Regularity of Monomial Ideals Gil Kalai Roy Meshulam Abstract For a simplicial complex X and a field K, let h i X) = dim H i X; K). It is shown that if X,Y are complexes
More informationClifford Algebras and Spin Groups
Clifford Algebras and Spin Groups Math G4344, Spring 2012 We ll now turn from the general theory to examine a specific class class of groups: the orthogonal groups. Recall that O(n, R) is the group of
More informationOn the singular elements of a semisimple Lie algebra and the generalized Amitsur-Levitski Theorem
On the singular elements of a semisimple Lie algebra and the generalized Amitsur-Levitski Theorem Bertram Kostant, MIT Conference on Representations of Reductive Groups Salt Lake City, Utah July 10, 2013
More informationOn the Alexander invariants of hypersurface complements
1 On the Alexander invariants of hypersurface complements Laurentiu Maxim Department of Mathematics, University of Illinois at Chicago, 851 S. Morgan St., Chicago, Illinois, 60607, USA E-mail: lmaxim@math.uic.edu
More informationON COSTELLO S CONSTRUCTION OF THE WITTEN GENUS: L SPACES AND DG-MANIFOLDS
ON COSTELLO S CONSTRUCTION OF THE WITTEN GENUS: L SPACES AND DG-MANIFOLDS RYAN E GRADY 1. L SPACES An L space is a ringed space with a structure sheaf a sheaf L algebras, where an L algebra is the homotopical
More informationMOTIVES ASSOCIATED TO SUMS OF GRAPHS
MOTIVES ASSOCIATED TO SUMS OF GRAPHS SPENCER BLOCH 1. Introduction In quantum field theory, the path integral is interpreted perturbatively as a sum indexed by graphs. The coefficient (Feynman amplitude)
More informationEtale homotopy theory (after Artin-Mazur, Friedlander et al.)
Etale homotopy theory (after Artin-Mazur, Friedlander et al.) Heidelberg March 18-20, 2014 Gereon Quick Lecture 1: Motivation March 18, 2014 Riemann, Poincare, Lefschetz: Until the early 20th century,
More informationINVARIANT DISTRIBUTIONS ON PROJECTIVE SPACES OVER LOCAL FIELDS
INVARIANT DISTRIBUTIONS ON PROJECTIVE SPACES OVER LOCAL FIELDS GUYAN ROBERTSON Abstract Let Γ be an Ãn subgroup of PGL n+1(k), with n 2, where K is a local field with residue field of order q and let P
More informationwhere m is the maximal ideal of O X,p. Note that m/m 2 is a vector space. Suppose that we are given a morphism
8. Smoothness and the Zariski tangent space We want to give an algebraic notion of the tangent space. In differential geometry, tangent vectors are equivalence classes of maps of intervals in R into the
More informationHYPERPLANE ARRANGEMENTS AND LINEAR STRANDS IN RESOLUTIONS
TRANSACTIONS OF THE AMERICAN MATHEMATICAL SOCIETY Volume 355, Number 2, Pages 609 618 S 0002-9947(02)03128-8 Article electronically published on September 6, 2002 HYPERPLANE ARRANGEMENTS AND LINEAR STRANDS
More informationGeometric Chevalley-Warning conjecture
Geometric Chevalley-Warning conjecture June Huh University of Michigan at Ann Arbor June 23, 2013 June Huh Geometric Chevalley-Warning conjecture 1 / 54 1. Chevalley-Warning type theorems June Huh Geometric
More informationNEW CLASSES OF SET-THEORETIC COMPLETE INTERSECTION MONOMIAL IDEALS
NEW CLASSES OF SET-THEORETIC COMPLETE INTERSECTION MONOMIAL IDEALS M. R. POURNAKI, S. A. SEYED FAKHARI, AND S. YASSEMI Abstract. Let be a simplicial complex and χ be an s-coloring of. Biermann and Van
More informationQUALIFYING EXAMINATION Harvard University Department of Mathematics Tuesday September 21, 2004 (Day 1)
QUALIFYING EXAMINATION Harvard University Department of Mathematics Tuesday September 21, 2004 (Day 1) Each of the six questions is worth 10 points. 1) Let H be a (real or complex) Hilbert space. We say
More informationREPRESENTATIONS OF FINITE GROUPS OF LIE TYPE: EXERCISES. Notation. 1. GL n
REPRESENTATIONS OF FINITE GROUPS OF LIE TYPE: EXERCISES ZHIWEI YUN Fix a prime number p and a power q of p. k = F q ; k d = F q d. ν n means ν is a partition of n. Notation Conjugacy classes 1. GL n 1.1.
More informationArtin-Schelter regular algebras and the Steenrod algebra
Artin-Schelter regular algebras and the Steenrod algebra J. H. Palmieri and J. J. Zhang University of Washington Los Angeles, 10 October 2010 Exercise Let A(1) be the sub-hopf algebra of the mod 2 Steenrod
More informationOral exam practice problems: Algebraic Geometry
Oral exam practice problems: Algebraic Geometry Alberto García Raboso TP1. Let Q 1 and Q 2 be the quadric hypersurfaces in P n given by the equations f 1 x 2 0 + + x 2 n = 0 f 2 a 0 x 2 0 + + a n x 2 n
More informationALEXANDER INVARIANTS OF HYPERSURFACE COMPLEMENTS
ALEXANDER INVARIANTS OF HYPERSURFACE COMPLEMENTS LAURENTIU MAXIM Abstract. These are notes I wrote for a series of lectures I gave at Tokyo University of Sciences and The University of Tokyo, Tokyo, Japan,
More informationKähler manifolds and variations of Hodge structures
Kähler manifolds and variations of Hodge structures October 21, 2013 1 Some amazing facts about Kähler manifolds The best source for this is Claire Voisin s wonderful book Hodge Theory and Complex Algebraic
More informationHomework 4: Mayer-Vietoris Sequence and CW complexes
Homework 4: Mayer-Vietoris Sequence and CW complexes Due date: Friday, October 4th. 0. Goals and Prerequisites The goal of this homework assignment is to begin using the Mayer-Vietoris sequence and cellular
More informationPart II. Algebraic Topology. Year
Part II Year 2017 2016 2015 2014 2013 2012 2011 2010 2009 2008 2007 2006 2005 2017 Paper 3, Section II 18I The n-torus is the product of n circles: 5 T n = } S 1. {{.. S } 1. n times For all n 1 and 0
More informationCharacteristic Classes, Chern Classes and Applications to Intersection Theory
Characteristic Classes, Chern Classes and Applications to Intersection Theory HUANG, Yifeng Aug. 19, 2014 Contents 1 Introduction 2 2 Cohomology 2 2.1 Preliminaries................................... 2
More informationL E C T U R E N O T E S O N H O M O T O P Y T H E O R Y A N D A P P L I C AT I O N S
L A U R E N T I U M A X I M U N I V E R S I T Y O F W I S C O N S I N - M A D I S O N L E C T U R E N O T E S O N H O M O T O P Y T H E O R Y A N D A P P L I C AT I O N S i Contents 1 Basics of Homotopy
More informationarxiv: v1 [math.ag] 28 Sep 2016
LEFSCHETZ CLASSES ON PROJECTIVE VARIETIES JUNE HUH AND BOTONG WANG arxiv:1609.08808v1 [math.ag] 28 Sep 2016 ABSTRACT. The Lefschetz algebra L X of a smooth complex projective variety X is the subalgebra
More informationTHE BNS-INVARIANT FOR THE PURE BRAID GROUPS
THE BNS-INVARIANT FOR THE PURE BRAID GROUPS NIC KOBAN, JON MCCAMMOND, AND JOHN MEIER Abstract. In 1987 Bieri, Neumann and Strebel introduced a geometric invariant for discrete groups. In this article we
More information