Weak point property and sections of Picard bundles on a compactified Jacobian over a nodal curve
|
|
- Allyson Bond
- 5 years ago
- Views:
Transcription
1 Proc. Indian Acad. Sci. (Math. Sci.) Vol. 126, No. 3, August 2016, pp DOI /s Weak point property and sections of Picard bundles on a compactified Jacobian over a nodal curve USHA N BHOSLE 1 and SANJAY SINGH 2, 1 Indian Institute of Science, Bangalore , India 2 Institute of Mathematics, Polish Academy of Sciences, Warsaw, Poland * Corresponding author. usnabh07@gmail.com; sanjayks@iiserb.ac.in MS received 13 December 2014; revised 28 May 2015 Abstract. We show that the compactified Jacobian (and its desingularization) of an integral nodal curve Y satisfies the weak point property and the Jacobian of Y satisfies the diagonal property. We compute some cohomologies of Picard bundles on the compactified Jacobian and its desingularization. Keywords. Weak point property; Picard bundle; compactified Jacobian; nodal curve Mathematics Subject Classification. Primary: 14H60; Secondary: 14D Introduction Debarre had proved that the Jacobian J 0 (X 0 ) of a smooth curve X 0 satisfies the diagonal property (Corollary 2.2 of [6]) i.e., there is a vector bundle of rank equal to the dimension of J 0 (X 0 ) over J 0 (X 0 ) J 0 (X 0 ), having a section whose zero scheme is the diagonal of J 0 (X 0 ) J 0 (X 0 ). In this note, we generalize Debarre s result to a singular curve X k with k ordinary double points (nodes). Following [12] (where the variety is assumed to be smooth), we say that a variety Z of dimension g has a weak point property if there is a vector bundle E of rank g on Z such that E has a section s whose zero scheme is a reduced point. If Z is a group variety, then this implies that Z satisfies the diagonal property. Let J 0 (X k ) be the generalized Jacobian of line bundles (locally free sheaves of rank 1) of degree 0 on X k. The variety J 0 (X k ) has a natural compactification J 0 (X k ),asthe variety of torsion-free sheaves of rank 1 and degree 0 on X k. We denote by J 0 (X k ) the natural desingularization of J 0 (X k ) (see subsection 2.1). Theorem 1.1. Let X k be an integral curve with k nodes (ordinary double points). (1) The variety J 0 (X k ) satisfies the weak point property. (2) The compactified Jacobian J 0 (X k ) satisfies the weak point property. (3) The generalized Jacobian J 0 (X k ) satisfies the diagonal property. (4) If X k is a rational curve, then J 0 (X k ) satisfies the diagonal property. As a corollary, we also prove that generalized Jacobians of some curves with many components satisfy the diagonal property. c Indian Academy of Sciences 329
2 330 Usha N Bhosle and Sanjay Singh Debarre proved the weak point property by computing the cohomology of a Picard bundle (see section 3 for definitions of Picard bundles) tensored with certain line bundles. For this, he used the identification of the Picard bundle on J 0 (X 0 ) with a symmetric product of X 0 in [9]. Unlike Debarre, we prove the weak point property by explicitly constructing suitable sections of Picard bundles on J 0 (X k ) and J 0 (X k ) and computing their zero schemes. Even in the non-singular case, our proof is simpler and more transparent than Debarre s proof. Moreover, Debarre s proof does not extend to nodal curves. On the nodal curve, the Picard bundle is not isomorphic to the symmetric product of the curve. One also uses the g-th Chern class of the Picard bundle to compute the zero scheme. The Chern classes (in the Chow group) of the Picard bundle on the Jacobian of a smooth curve were computed by Mattuck. The Chern classes of the Picard bundle on J 0 (X k ) are not known, those (modulo numerical equivalence) of the Picard bundle on J 0 (X k ) were computed by one of the authors [3]. Using that, we first prove the weak point property for J 0 (X k ) and deduce that for J As a corollary, we determine the first and top Chern classes of the Picard bundles in the Chow group (Corollary 4.4). We also compute all the cohomologies of the Picard bundle on J 0 (X k ) and the 0-th and top cohomologies of the Picard bundles on J 0 (X k ) (Proposition 4.5). 2. Preliminaries 2.1 The compactified Jacobian and its desingularization For a positive integer k, letx k denote an irreducible projective nodal curve with k nodes over an algebraically closed field C. Lety 1,...,y k be the nodes of X k.letg(x k ) be the arithmetic genus of X k. We denote by ω Xk the locally free dualizing sheaf on X k.let p k : X 0 X k be the normalization map. Let p k 1 (y i ) := {x i,z i } X 0 be the inverse image of the nodal point y i in X k. By abuse of notation, we denote by the same x i and z i, the images of these points in X j, for all i>jand y i the nodes in X j for 1 i j. Fix, once and for all, a base point t X 0 different from all x j,y j,j = 1,...,k and sufficiently general. We denote its image in X j again by t.let p k : X k 1 X k be the natural morphism obtained by identifying x k and z k to the node y k. For d Z,letJ d (X k ) be the Jacobian of line bundles (locally free sheaves of rank 1) of degree d on X k. The variety J d (X k ) has a natural compactification J d (X k ), as the variety of torsion-free sheaves of rank 1 and degree d on X k. A natural desingularization J d (X k ) of J d (X k ) can be defined inductively as follows. Let L d k 1 be the Poincaré sheaf on J d (X k 1 ) X k 1 normalised by the condition that its restriction to J d (X k 1 ) t is trivial. Let ( L d k 1 ) x k (respectively ( L d k 1 ) z k ) be the line bundle on J d (X k 1 ) obtained by restricting L d k 1 to J d (X k 1 ) x k (respectively J d (X k 1 ) z k ). Then,by Proposition 12.1, p. 64 of [11], J d (X k ) = P(( L d k 1 ) x k ( L d k 1 ) z k ).
3 Picard bundles 331 Let π k : J d (X k ) J d (X k 1 ) be the canonical projection and define π k : J d (X k ) J d (X 0 ), π k := π 1 π k. There is a birational surjective map h : J d (X k ) J d (X k ). We denote by the same letter h such a map for all d (if no confusion arises). The subset J d (X k ) is a smooth open subset of J d (X k ), it is also an open subset of J d (X k ) and h is an isomorphism over J d (X k ). 2.2 Picard bundles on J 0 (X k ) and J(X k ) Let L k be the (normalised) Poincaré sheaf on J 0 (X k ) X k. We denote the two projections of J 0 (X k ) X k by ν k and q k respectively. Let L k(d) denote the Poincaré sheaf twisted by the pullback of the line bundle O Xk (dt), where t X k is the fixed smooth point. We define the direct image sheaves Ē d,k := ν k (L k(d)). These sheaves are vector bundles on J 0 (X k ) if d 2g(X k ) 1 and are called Picard bundles on J Let L k be the pullback of L k to J 0 (X k ) X k by h id. We denote the two projections of J 0 (X k ) X k by ν k and q k respectively. The direct image sheaves E d,k := ν k ( L k (d)) are vector bundles on J 0 (X k ) if d 2g(X k ) 1 and are called Picard bundles on J One has h Ē d,k = Ed,k. We may identify J 0 (X k ) with J d (X k ) by the isomorphism L L(dt) for L J 0 (X k ) and L k (d) with L d k. Then we call the pullback of E d,k to J d (X k ) as the Picard bundle on J d (X k ) (for d 2g(X k ) 1), it is the direct image of L d k on J d (X k ). Recall that J 0 (X k ) = P(( L k 1 ) xk ( L k 1 ) zk ).Letπ k : J 0 (X k ) J 0 (X k 1 ) be the projection map, which is a P 1 bundle. There is an exact sequence i k 0 E d,k πk E d,k 1 OJ 0 (X k ) (1) 0, (Proposition 5.1 of [5]). Dualizing this sequence gives the exact sequence 0 OJ 0 (X k ) ( 1) π k i E k d,k 1 Ed,k 0. (2.1)
4 332 Usha N Bhosle and Sanjay Singh Remark 2.1. Let ψ : J 0 (X k ) J 0 (X k ) be the isomorphism defined by L ω Xk O Xk ( (2g(X k ) 2)t) L, where t X k is a smooth point. Using Serre duality on X k, it is easy to see that Ē d,k = ψ F 2g 2 d,k, where F d,k := R 1 p ν (L k (d)). 3. Sections of Picard bundles Write P k := L k (d) on J The fiber of Ē d,k over L H 0 (X k, L(d)). Hence there is an evaluation map EV k : ν (Ē d,k ) P k, J 0 (X k ) is isomorphic to defined by (L,y,φ) φ(y), for L J 0 (X k ), y X k,φ H 0 (X k, L(d)). Restricting EV k to J 0 (X k ) {t}, we get ev k : Ē d,k P k J 0 (X k ) {t}. By our assumption, we have P k J 0 (X k ) {t} = OJ Hence we have ev k : Ē d,k O J 0 (X k ). Dualizing, we get ev k : O J 0 (X k ) Ē d,k or equivalently, Let σ k H 0 ( J 0 (X k ), Ē d,k ). σ k H 0 ( J 0 (X k ), E d,k ) denote the pull back of σ k. Since h is an isomorphism over J 0 (X k ), we identify J 0 (X k ) with h 1 J Lemma 3.1. Let N be a torsion free sheaf of rank 1 and degree 2g(X k ) 2 on X k. Then dim H 0 (X k,n)= g if and only if N = ω Xk. Proof. For a torsion free sheaf N of rank 1 and degree 2g(X k ) 2, by Riemann Roch theorem, h 0 (X k,n)= g if and only if h 1 (X k,n)= 1. By Serre duality, this is equivalent to h 0 (X k,ω Xk N ) = 1. Thus ω Xk N is a torsion free sheaf of rank 1 and degree 0 with a nonzero section which must be nowhere vanishing and hence generates the trivial line bundle. Thus ω Xk N is the trivial line bundle i.e., ω Xk = N. PROPOSITION 3.2 (1) If d 2g(X k ), then σ k and σ k are nowhere vanishing sections. (2) If d = 2g(X k ) 1, then each of σ k and σ k has its zero set consisting of one point, the point p J 0 (X k ) corresponding to the line bundle ω Xk ( (2g(X k ) 2)t) on X k. Proof. Let L J Then H 1 (X k, L(d)) = 0ford 2g(X k ) 1. The section σ k vanishes at L J 0 (X k ) if and only if the restriction of ev k to the fiber over L is identically
5 Picard bundles 333 zero, or equivalently, the restriction of ev k to the fiber of Ē d,k over L is identically zero, i.e. φ(t) = 0 for all φ H 0 (X k, L(d)). (1) If d 2g(X k ), then H 0 (X k, L(d)) generates the fiber L(d) t at t for all L. Hence φ(t) = 0forsomeφ H 0 (X k, L(d)) and hence σ k does not vanish at L for any L J (2) Note that φ(t) = 0 for all φ H 0 (X k, L(d)) if and only if H 0 (X k, L(d)) = H 0 (X k, L(d) O Xk ( t)) = H 0 (X k,l(d 1)). Ford = 2g(X k ) 1, h 0 (X k, L(d)) = g and H 0 (X k, L(d)) = H 0 (X k,l(d 1)) if and only if h 0 (X k,l(d 1)) = g. By Lemma 3.1, H 0 (X k,l(d 1)) = g if and only if L(d 1) = ω Xk i.e. L = ω Xk (( 2g(X k ) + 2)t). This proves part (2). Recall that for any k, there is an exact sequence (2.1) 0 OJ 0 (X k ) ( 1) π k i E k d,k 1 Ed,k 0. This gives a map on sections H 0 (i k ) : H 0 ( J 0 (X k ), π k E d,k 1 ) H 0 ( J 0 (X k ), E d,k ). Define i k by i k = i 0 i k. Then one has i k : π k E d,0 E d,k. The following lemma shows that σ k is the image of a section coming from a section of E d,0. Lemma 3.3 (1) The map H 0 (i k ) maps π k (σ k 1) to σ k. (2) The map H 0 (i k ) maps π k (σ 0 ) to σ k. Proof. Consider (L 0,Q 1,...,Q k ) J 0 (X k ), L 0 J 0 (X 0 ). Let h(l 0,Q 1,..., Q k 1 ) = L 1,h(L 0,Q 1,...,Q k ) = L. Then there is a commutative diagram D 1 : H 0 (X k,π k L 1 (d)) = H 0 (X k 1,L 1 (d)) ev k 1 C H 0 ev k (X k, L(d)) C The diagram D 1 implies that there is a commutative diagram D 2 : πk (E d,k 1) π k ev k 1 E d,k ev k O J 0 (X k ) O J 0 (X k ). The diagram D 2 implies that π k 1 (σ k 1) is mapped to σ k by H 0 (i k ). The second assertion follows inductively from the first.
6 334 Usha N Bhosle and Sanjay Singh 4. Weak point property and diagonal property Following [12] (where the variety is assumed to be smooth), we make the following definitions. DEFINITION 4.1 A variety Z of dimension n satisfies the weak point property if there is a vector bundle E of rank n on Z such that E has a section s whose zero scheme is a reduced point. DEFINITION 4.2 A variety Z of dimension n satisfies the diagonal property if there is a vector bundle E of rank n on Z Z such that E has a section s whose zero scheme is the diagonal of Z Z. If Z is a group variety, then Z satisfies the diagonal property if it satisfies the weak point property. Let X k be an integral curve with k nodes (ordinary double points). Let σ k be the section of Ed,k defined in Section 3. Theorem 4.3. Let X k be an integral curve with k nodes and d = 2g(X k ) 1. (1) The zero scheme of σ k is the reduced point {p}. Thus J 0 (X k ) satisfies the weak point property. (2) The compactified Jacobian J 0 (X k ) satisfies the weak point property. (3) The generalized Jacobian J 0 (X k ) satisfies the diagonal property. (4) If X k is a rational curve, then J 0 (X k ) satisfies the diagonal property. Proof. (1) Let Z(σ k ) denote the zero scheme of σ k and A 0 (Z(σ k )) the Chow group of zero cycles on Z(σ k ) modulo rational equivalence. We associate to Z(σ k ) the local top Chern class Z(σ k ) A 0 (Z(σ k )) of Ed,k with respect to σ k (Chapter 14 of [8]). Since J 0 (X k ) is Cohen Macaulay and the dimension of the zero scheme of σ k equals dimension J 0 (X k ) r(ed,k ), by Example of [8], the section σ k is regular, and Z(σ k ) =[Z(σ k )], the cycle defined by the natural scheme structure on Z(σ k ). By Proposition 14.1 of [8], the image of Z(σ k ) in A 0 ( J 0 (X k )) is i Z(σ k ) [X], where i : Z(σ k ) J 0 (X k ) is the inclusion and [X] denotes the fundamental class of X. This implies that the degree of the top Chern class (i.e., the top Chern class evaluated at the fundamental cycle of J 0 (X k ))ofed,k equals the degree of the cycle associated with the zero scheme of σ k. Since c g (Ed,k ) equals the class of a (reduced) point in cycles modulo numerical equivalence (Theorem 1.1 of [3]), the degree of the cycle associated to the zero scheme of σ k is 1. Therefore it must be a reduced point. Thus σ k has a simple zero at p. (2) Since h is an isomorphism over the open set J 0 (X k ), it follows that σ k has a simple zero at p. Thus both J 0 (X k ) and J 0 (X k ) satisfy the weak point property. (3) The proofs of (1) and (2) show that, in particular, J 0 (X k ) satisfies the weak point property. Since J 0 (X k ) is a group variety and the diagonal property is equivalent to the weak point property for group varieties (Proposition 13 of [12]), it follows that
7 Picard bundles 335 J 0 (X k ) satisfies the diagonal property. More precisely, if m and i respectively denote the multiplication and inverse on J 0 (X k ) and f : J 0 (X k ) J 0 (X k ) J 0 (X k ) is the map defined by (a, b) m(m(a, i(b)), p) then the section f (σ k ) of f (Ed,k ) has zero scheme precisely the diagonal. (4) If X k is a rational curve, then J 0 (X k ) = P 1 P 1, a k-fold product (Section 9 of [3]). Since P 1 satisfies the diagonal property, its k-fold product also satisfies the diagonal property proving part (4). COROLLARY 4.4 Let d = 2g(X k ) 1. (1) The g-th Chern class c g (Ed,k ) = W 0 in the Chow group of J (2) The g-th Chern class c g (Ēd,k ) = W 0 in the Chow group of J (3) The first Chern class c 1 (E d,k ) = c 1(det E d,k ) = θ k,c 1 (Ē d,k ) = c 1(det Ē d,k ) in the Chow group. Here θ k is the pull back of the theta divisor on J 0 (X k ) to J det E d,k = O J 0 (X k ) (θ k), the line bundle associated to the divisor θ k. Proof. Since J 0 (X k ) satisfies the weak point property (Theorem 4.3), one has c g (E d,k ) =[p] CHg ( J 0 (X k )), c 1 (E d,k ) = c 1(det E d,k ) CH1 ( J 0 (X k )) (subsection 4.2 of [12]). Under the isomorphism J 0 (X k ) J 0 (X k ) defined by L ω Xk O Xk ( (2g(X k ) 2)t) L, the point W 0 J 0 (X k ) corresponding to O Xk maps to p, hence part (1) follows. Part (2) follows similarly from the fact that σ k has a simple zero at p. We shall prove part (3) by induction on k, the number of nodes. The result is true for k = 0 [9, Corollary to Theorem 3]. Assume the result for X k 1. For 0 m g, letw m,k J 0 (X k ) denote the cycle determined by the Brill-Noether locus of L J 0 (X k ) such that h 0 (X k, L(m)) > 0. We denote by W m,k its pull back to J From the proof of Lemma 3.7 of [4], for 1 m g(x k ) one has W m,k = πk 1 ( W m,k 1 ) S xk + πk 1 ( W m 1,k 1 ), where S xk is a divisor defined by a section of OJ 0 (X k ) (1). Form = g(x k) 1, using the facts that g(x k 1 ) = g(x k ) 1 and W g(xk 1 ),k 1 = J 0 (X k 1 ), one has W g(xk ) 1,k = S xk + π 1 k W g(xk 1 ) 1,k 1.
8 336 Usha N Bhosle and Sanjay Singh By induction, c 1 (Ed,k 1 ) = W g(xk 1 ) 1,k 1. Hence W g(xk ) 1,k = S xk + πk c 1(Ed,k 1 ). From the exact sequence (2.1), we have c 1 (Ed,k ) = S x k +πk c 1(Ed,k 1 ). Thus c 1(Ed,k ) = W g(xk ) 1,k = θ k. Since rational equivalence coincides with linear equivalence for divisors on normal varieties, c 1 (det Ed,k ) = θ k CH 1 ( J 0 (X k )) implies the last statement in part (3). The Chern classes of the Picard bundle E d,k,d 2g(X k) 1, modulo numerical equivalence were computed in Theorem 1.1 of [3]. It was believed that they were the same in the Chow group also. This is taken up by the first named author in a subsequent paper. The following proposition shows, in particular, that if the curve X k is not rational then the section σ k is unique up to a scalar. PROPOSITION 4.5 Let d 2g(X k ) 1. (1) π k Ed,k = Ed,k 1,πk E d,k = Ed,0,(Ri π k ) Ed,k = 0 for i>0. (2) For g(x 0 ) 1, h 0 ( J 0 (X k ), Ed,k ) = 1. (3) Let g(x 0 ) 1. Then h i ( J 0 (X k ), Ed,k ) = (g(x 0 ) 1)C i for 1 i<g(x 0 ), h i ( J 0 (X k ), Ed,k ) = 0 for i g(x 0). (4) For g(x 0 ) 1, h 0 ( J 0 (X k ), Ēd,k ) = 1. (5) For g(x 0 ) = 0, h 0 ( J 0 (X k ), Ed,k ) = d + 1, h0 ( J 0 (X k ), E d,k ) = d 2k + 1. (6) h g ( J 0 (X k ), Ēd,k ) = 0, h0 ( J 0 (X k ), Ē d,k ) = 0. Proof. (1) By taking the direct image of the exact sequence (2.1) and using the facts that π k πk E d,k = Ed,k, Ri π k O Pk ( 1) = 0 for all i 0, we have π k Ed,k = Ed,k 1, (Ri π k ) Ed,k = 0fori > 0. Since π k = π 0 π k, inductively we get π ke d,k = Ed,0,(Ri π k ) Ed,k = 0 for all i>0. (2) and (3) There is a Leray spectral sequence with Ep,q 2 = H p ( J 0 (X k ), (R q π k ) Ed,k ) which abuts to H p+q ( J 0 (X k ), Ed,k ). By Part (1), π k Ed,k = Ed,k 1, (Ri π k ) Ed,k = 0fori > 0. Hence the Leray spectral sequence gives H i ( J 0 (X k ), Ed,k ) = H i ( J 0 (X k 1 ), Ed,k 1 ) for all non-negative i and positive k. By induction on k, one has H i ( J 0 (X k ), Ed,k ) = H i ( J 0 (X 0 ), Ed,0 ), i 0. If g(x 0 ) 2, by Proposition 4.4 of [10], h 0 ( J 0 (X 0 ), Ed,0 ) = 1 and hi ( J 0 (X 0 ), Ed,0 ) = (g(x 0 ) 1)C i for 1 i < g(x 0 ),h g(x0) ( J 0 (X 0 ), Ed,0 ) = 0. Certainly, h i ( J 0 (X 0 ), Ed,0 ) = 0fori>g(X 0). If g(x 0 ) = 1, one has J 0 (X 0 ) = X 0. Since k 1,g(X k ) 2 and hence d 3. By the main theorem of [7], for d 2 the Picard bundle Ed,0 is a stable vector bundle of rank d, slope 1/d > 2g(X 0 ) 2. Hence h i ( J 0 (X 0 ), Ed,0 ) = 0, i > 0. Then by Riemann Roch theorem, h 0 ( J 0 (X 0 ), E d,0 ) = 1. It follows that h0 ( J 0 (X k ), E d,k ) = 1 and h i ( J 0 (X k ), E d,k ) = 0fori>0.
9 Picard bundles 337 This completes the proof of Parts (2) and (3). (4) Recall that Ed,k = h Ēd,k. Since J 0 (X k ) is irreducible and h is a surjective birational map, it follows that the map H 0 ( J 0 (X k ), Ēd,k ) H 0 ( J 0 (X k ), Ed,k ), defined by pull back of sections, is injective. Since 0 = σ k H 0 ( J 0 (X k ), Ēd,k ),itfollowsfrompart(2) that H 0 ( J 0 (X k ), Ẽd,k ) = 1. (5) By Proposition 9.1 of [5], E d,k = I d 2k+1 i O Pi (1), where I n denotes the trivial vector bundle of rank n for any positive integer n. Since h 0 (I n ) = n, h 0 ( J 0 (X k ), O Pi (1)) = 2, Part (5) follows. Note that d 2g(X k ) 1 = 2k 1sothath 0 ( J 0 (X k ), E d,k ) = d + 1 2k 0. (6) Since ωj 0 (X k ) = OJ 0 (X k ) [1], to prove Part (6) it suffices to show that h0 ( J 0 (X k ), Ē d,k ) = 0. For convenience, we work on J d (X k ) rather than J For every L J d 1 (X k ), we have an embedding of X k in J d (X k ) defined by x L Ix, where I x is the ideal sheaf of x. LetX k,l denote the image of X k under this embedding. If g(x 0 ) 1, then by the proof of Theorem 8.10 of [5] (or equivalently, Proposition 6.1, Lemmas 8.7, 8.8, 8.9 of [5]), the vector bundle Ē d,k Xk,L is stable if d 2g(X k ) and it is semistable if d = 2g(X k ) 1. If X k is a rational nodal curve, then by the proof of Theorem 9.3 of [5], Ē d,k Xk,L is stable. By Proposition 8.8(1) of [5], Ē d,k (t) Xk,L,t being a fixed smooth point, has degree d + 1 2g(X k ) and rank d + 1 g(x k ). Hence Ē d,k Xk,L has degree g(x k )<0. It follows that h 0 (X k,l, Ē d,k Xk,L ) = 0. Thus any section of Ē d,k vanishes on X k,l for all L J d 1 (X k ).IfN J d (X k ), then N X k,l where L = N O( t). Hence any section s of Ē d,k vanishes over J d (X k ). Since J d (X k ) is an open dense subset of J d (X k ), it follows that s = 0. Lemma 4.6. Let X be a Gorenstein projective variety of dimension g. Let E be a vector bundle of rank g on X with a section s such that the zero scheme of s is a reduced smooth point. Then all (non-zero) sections of det(e) ω X vanish at x. Proof. This follows exactly as Proposition 3.1 of [6] using the fact that ω X is locally free. COROLLARY 4.7 All (non-zero) sections of det(ē d,k ), d = 2g(X k) 1, vanish at p. Proof. Since the singularities of X k are of embedding dimension 2, by the main result of [2], the variety J 0 (X k ) is a local complete intersection and hence Gorenstein. Therefore the result follows from Theorem 4.3 and Lemma 4.6 using the fact that ω J 0 (X k ) = OJ 0 (X k ) (Lemma 4.2 of [1]). Lemma 4.8. The line bundle (det Ed,k ) ω J 0 (X k ) has no non-zero sections.
10 338 Usha N Bhosle and Sanjay Singh Proof. From the exact sequence of Proposition 5.2 of [5], taking determinants, we get det E d,k = π k (det E d,0 ) i O Pi (1).Since ω J 0 (X k ) = i O Pi ( 2), wehave (det E d,k ) ω J 0 (X k ) = π k (det E d,0 ) i O Pi ( 1). Taking direct image on J 0 (X k ), we get π k (det E d,k ω J 0 (X k ) ) = (det E d,0 ) π k ( io Pi ( 1)) = 0. Hence H 0 ( J 0 (X k ), (det Ed,k ) ω J 0 (X k ) ) = H 0 ( J 0 (X 0 ), π k(det E d,k ω J 0 (X k ) )) = Curves with many components Consider a connected reduced curve Y with many irreducible components Y i,i I such that Y has only ordinary double points as singularities. The dual graph of such a curve is a graph whose vertices v i I correspond to the Y i s and the edges e j correspond to the singular points y j. Two vertices v i and v i are connected by an edge e j if and only if Y i and Y i have y j as a node. Then a node y j lying on a single component Y i corresponds to a loop at v i. Suppose that the graph obtained by forgetting such loops in the graph of Y is a tree, or equivalently, the graph of the curve obtained by blowing up all nodes of Y, which lie on a single irreducible component (and no other component), is a tree. Simple examples of such Y are chains of smooth curves, or more generally a tree-like curve i.e., a curve whose dual graph is a tree. COROLLARY 4.9 Suppose that Y is a curve as in subsection 4.1. Then the diagonal property holds for the generalized Jacobian of Y. Proof. This follows from Theorem 4.3 as the generalized Jacobian of Y is isomorphic to the product of generalized Jacobians of Y i,i I. Acknowledgements The authors would like to thank the referee for useful comments, one of which led to improvement of results in Proposition 4.5(3). This work was done during the tenure of the first author in Indian Institute of Science, Bangalore, as a Raja Ramanna Fellow. The second author (SS) thanks Prof. Piotr Pragacz for motivating to study the diagonal and the point property, and is supported by the Post-Doctoral Research Fellowship of Institute of Mathematics, Polish Academy of Sciences. References [1] Alexeev V and Nakamura I, Mumford s construction of degenerating Abelian varieties, Tohoku Math. J. 51 (1999) [2] Altman A, Iarrobino A and Kleiman S, Irreducibility of the compactified Jacobian, Real and complex singularities, in: Proc. 9th Nordic Summer School (1977) (Oslo: Sijthoff and Noordhoff) pp
11 Picard bundles 339 [3] Bhosle Usha N, Maps into projective spaces, Proc. Indian Acad. Sci. (Math. Sci.) 123(3) (2013) [4] Bhosle Usha N and Parameswaran A J, On the Poincaré formula and Riemann singularity theorem over nodal curves, Math. Ann. 342(4) (2008) [5] Bhosle Usha N and Parameswaran A J, Picard bundles and Brill-Noether loci on the compactified Jacobian of a nodal curve, IMRN 2014(15) (2014) doi: /imrn/rnt069 [6] Debarre O, The diagonal property for abelian varieties, Curves and abelian varieties, in: Contemp. Math., 465 (2008) (Providence, RI: Amer. Math. Soc.) pp [7] Ein L and Lazarsfeld R, Stability and restrictions of Picard bundles with an application to the normal bundles of elliptic curves, in: Complex projective geometry (ed) Ellingsrud, Peskine et al LMS 179 (1992) (Cambridge University Press) [8] Fulton, Intersection theory, 2nd ed. (1998) (Berlin Heidelberg: Springer-Verlag) [9] Mattuck A, Symmetric products and Jacobians, Amer. J. Math. 83 (1961) [10] Mukai S, Duality between D(X) and D( ˆX) with its applications to Picard sheaves, Nagoya Math. J. 81 (1981) [11] Oda T and Seshadri C S, Compactifications of the generalised Jacobian variety, Transactions of the Amer. Math. Soc. 253 (1979) 1 90 [12] Pragacz P, Srinivas V and Pati V, Diagonal subschemes and vector bundles, Pure Appl. Math. Quart. 4 (2008) COMMUNICATING EDITOR: Nitin Nitsure
The diagonal property for abelian varieties
The diagonal property for abelian varieties Olivier Debarre Dedicated to Roy Smith on his 65th birthday. Abstract. We study complex abelian varieties of dimension g that have a vector bundle of rank g
More informationPorteous s Formula for Maps between Coherent Sheaves
Michigan Math. J. 52 (2004) Porteous s Formula for Maps between Coherent Sheaves Steven P. Diaz 1. Introduction Recall what the Thom Porteous formula for vector bundles tells us (see [2, Sec. 14.4] for
More informationPacific Journal of Mathematics
Pacific Journal of Mathematics STABLE REFLEXIVE SHEAVES ON SMOOTH PROJECTIVE 3-FOLDS PETER VERMEIRE Volume 219 No. 2 April 2005 PACIFIC JOURNAL OF MATHEMATICS Vol. 219, No. 2, 2005 STABLE REFLEXIVE SHEAVES
More informationON DEGENERATIONS OF MODULI OF HITCHIN PAIRS
ELECRONIC RESEARCH ANNOUNCEMENS IN MAHEMAICAL SCIENCES Volume 20, Pages 105 110 S 1935-9179 AIMS (2013) doi:10.3934/era.2013.20.105 ON DEGENERAIONS OF MODULI OF HICHIN PAIRS V. BALAJI, P. BARIK, AND D.S.
More informationLECTURE 7: STABLE RATIONALITY AND DECOMPOSITION OF THE DIAGONAL
LECTURE 7: STABLE RATIONALITY AND DECOMPOSITION OF THE DIAGONAL In this lecture we discuss a criterion for non-stable-rationality based on the decomposition of the diagonal in the Chow group. This criterion
More informationTheta divisors and the Frobenius morphism
Theta divisors and the Frobenius morphism David A. Madore Abstract We introduce theta divisors for vector bundles and relate them to the ordinariness of curves in characteristic p > 0. We prove, following
More informationDUALITY SPECTRAL SEQUENCES FOR WEIERSTRASS FIBRATIONS AND APPLICATIONS. 1. Introduction
DUALITY SPECTRAL SEQUENCES FOR WEIERSTRASS FIBRATIONS AND APPLICATIONS JASON LO AND ZIYU ZHANG Abstract. We study duality spectral sequences for Weierstraß fibrations. Using these spectral sequences, we
More informationAPPENDIX 3: AN OVERVIEW OF CHOW GROUPS
APPENDIX 3: AN OVERVIEW OF CHOW GROUPS We review in this appendix some basic definitions and results that we need about Chow groups. For details and proofs we refer to [Ful98]. In particular, we discuss
More informationALGEBRAIC HYPERBOLICITY OF THE VERY GENERAL QUINTIC SURFACE IN P 3
ALGEBRAIC HYPERBOLICITY OF THE VERY GENERAL QUINTIC SURFACE IN P 3 IZZET COSKUN AND ERIC RIEDL Abstract. We prove that a curve of degree dk on a very general surface of degree d 5 in P 3 has geometric
More informationNon-uniruledness results for spaces of rational curves in hypersurfaces
Non-uniruledness results for spaces of rational curves in hypersurfaces Roya Beheshti Abstract We prove that the sweeping components of the space of smooth rational curves in a smooth hypersurface of degree
More informationGeometry of the theta divisor of a compactified jacobian
J. Eur. Math. Soc. 11, 1385 1427 c European Mathematical Society 2009 Lucia Caporaso Geometry of the theta divisor of a compactified jacobian Received October 16, 2007 and in revised form February 21,
More informationAbelian Varieties and the Fourier Mukai transformations (Foschungsseminar 2005)
Abelian Varieties and the Fourier Mukai transformations (Foschungsseminar 2005) U. Bunke April 27, 2005 Contents 1 Abelian varieties 2 1.1 Basic definitions................................. 2 1.2 Examples
More informationIf F is a divisor class on the blowing up X of P 2 at n 8 general points p 1,..., p n P 2,
Proc. Amer. Math. Soc. 124, 727--733 (1996) Rational Surfaces with K 2 > 0 Brian Harbourne Department of Mathematics and Statistics University of Nebraska-Lincoln Lincoln, NE 68588-0323 email: bharbourne@unl.edu
More informationOn a theorem of Ziv Ran
INSTITUTUL DE MATEMATICA SIMION STOILOW AL ACADEMIEI ROMANE PREPRINT SERIES OF THE INSTITUTE OF MATHEMATICS OF THE ROMANIAN ACADEMY ISSN 0250 3638 On a theorem of Ziv Ran by Cristian Anghel and Nicolae
More informationSERRE FINITENESS AND SERRE VANISHING FOR NON-COMMUTATIVE P 1 -BUNDLES ADAM NYMAN
SERRE FINITENESS AND SERRE VANISHING FOR NON-COMMUTATIVE P 1 -BUNDLES ADAM NYMAN Abstract. Suppose X is a smooth projective scheme of finite type over a field K, E is a locally free O X -bimodule of rank
More informationStable maps and Quot schemes
Stable maps and Quot schemes Mihnea Popa and Mike Roth Contents 1. Introduction........................................ 1 2. Basic Setup........................................ 4 3. Dimension Estimates
More informationLECTURES ON SINGULARITIES AND ADJOINT LINEAR SYSTEMS
LECTURES ON SINGULARITIES AND ADJOINT LINEAR SYSTEMS LAWRENCE EIN Abstract. 1. Singularities of Surfaces Let (X, o) be an isolated normal surfaces singularity. The basic philosophy is to replace the singularity
More informationDiagonal Subschemes and Vector Bundles
Pure and Applied Mathematics Quarterly Volume 4, Number 4 (Special Issue: In honor of Jean-Pierre Serre, Part 1 of 2 ) 1233 1278, 2008 Diagonal Subschemes and Vector Bundles Piotr Pragacz, Vasudevan Srinivas
More informationAlgebraic Geometry Spring 2009
MIT OpenCourseWare http://ocw.mit.edu 18.726 Algebraic Geometry Spring 2009 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms. 18.726: Algebraic Geometry
More informationSegre classes of tautological bundles on Hilbert schemes of surfaces
Segre classes of tautological bundles on Hilbert schemes of surfaces Claire Voisin Abstract We first give an alternative proof, based on a simple geometric argument, of a result of Marian, Oprea and Pandharipande
More informationSPACES OF RATIONAL CURVES IN COMPLETE INTERSECTIONS
SPACES OF RATIONAL CURVES IN COMPLETE INTERSECTIONS ROYA BEHESHTI AND N. MOHAN KUMAR Abstract. We prove that the space of smooth rational curves of degree e in a general complete intersection of multidegree
More informationARITHMETICALLY COHEN-MACAULAY BUNDLES ON THREE DIMENSIONAL HYPERSURFACES
ARITHMETICALLY COHEN-MACAULAY BUNDLES ON THREE DIMENSIONAL HYPERSURFACES N. MOHAN KUMAR, A. P. RAO, AND G. V. RAVINDRA Abstract. We prove that any rank two arithmetically Cohen- Macaulay vector bundle
More informationA CRITERION FOR A DEGREE-ONE HOLOMORPHIC MAP TO BE A BIHOLOMORPHISM. 1. Introduction
A CRITERION FOR A DEGREE-ONE HOLOMORPHIC MAP TO BE A BIHOLOMORPHISM GAUTAM BHARALI, INDRANIL BISWAS, AND GEORG SCHUMACHER Abstract. Let X and Y be compact connected complex manifolds of the same dimension
More informationAFFINE PUSHFORWARD AND SMOOTH PULLBACK FOR PERVERSE SHEAVES
AFFINE PUSHFORWARD AND SMOOTH PULLBACK FOR PERVERSE SHEAVES YEHAO ZHOU Conventions In this lecture note, a variety means a separated algebraic variety over complex numbers, and sheaves are C-linear. 1.
More informationLECTURE 6: THE ARTIN-MUMFORD EXAMPLE
LECTURE 6: THE ARTIN-MUMFORD EXAMPLE In this chapter we discuss the example of Artin and Mumford [AM72] of a complex unirational 3-fold which is not rational in fact, it is not even stably rational). As
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 informationSPACES OF RATIONAL CURVES ON COMPLETE INTERSECTIONS
SPACES OF RATIONAL CURVES ON COMPLETE INTERSECTIONS ROYA BEHESHTI AND N. MOHAN KUMAR Abstract. We prove that the space of smooth rational curves of degree e on a general complete intersection of multidegree
More informationmult V f, where the sum ranges over prime divisor V X. We say that two divisors D 1 and D 2 are linearly equivalent, denoted by sending
2. The canonical divisor In this section we will introduce one of the most important invariants in the birational classification of varieties. Definition 2.1. Let X be a normal quasi-projective variety
More informationARITHMETICALLY COHEN-MACAULAY BUNDLES ON HYPERSURFACES
ARITHMETICALLY COHEN-MACAULAY BUNDLES ON HYPERSURFACES N. MOHAN KUMAR, A. P. RAO, AND G. V. RAVINDRA Abstract. We prove that any rank two arithmetically Cohen- Macaulay vector bundle on a general hypersurface
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 informationGeometry of the Theta Divisor of a compactified Jacobian
Geometry of the Theta Divisor of a compactified Jacobian Lucia Caporaso 1 Abstract. The object of this paper is the theta divisor of the compactified Jacobian of a nodal curve. We determine its irreducible
More informationarxiv: v1 [math.ag] 3 Mar 2018
CLASSIFICATION AND SYZYGIES OF SMOOTH PROJECTIVE VARIETIES WITH 2-REGULAR STRUCTURE SHEAF SIJONG KWAK AND JINHYUNG PARK arxiv:1803.01127v1 [math.ag] 3 Mar 2018 Abstract. The geometric and algebraic properties
More informationCOMPLEX ALGEBRAIC SURFACES CLASS 9
COMPLEX ALGEBRAIC SURFACES CLASS 9 RAVI VAKIL CONTENTS 1. Construction of Castelnuovo s contraction map 1 2. Ruled surfaces 3 (At the end of last lecture I discussed the Weak Factorization Theorem, Resolution
More informationChern numbers and Hilbert Modular Varieties
Chern numbers and Hilbert Modular Varieties Dylan Attwell-Duval Department of Mathematics and Statistics McGill University Montreal, Quebec attwellduval@math.mcgill.ca April 9, 2011 A Topological Point
More informationMath 248B. Applications of base change for coherent cohomology
Math 248B. Applications of base change for coherent cohomology 1. Motivation Recall the following fundamental general theorem, the so-called cohomology and base change theorem: Theorem 1.1 (Grothendieck).
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 informationRESEARCH STATEMENT: COMPACTIFYING RELATIVE PICARD SCHEMES
RESEARCH STATEMENT: COMPACTIFYING RELATIVE PICARD SCHEMES ATOSHI CHOWDHURY 1. Introduction 1.1. Moduli spaces and compactification. My research is in the area of algebraic geometry concerned with moduli
More informationMODULI SPACES OF CURVES
MODULI SPACES OF CURVES SCOTT NOLLET Abstract. My goal is to introduce vocabulary and present examples that will help graduate students to better follow lectures at TAGS 2018. Assuming some background
More informationCOMPACTIFYING THE RELATIVE PICARD FUNCTOR OVER DEGENERATIONS OF VARIETIES
COMPACTIFYING THE RELATIVE PICARD FUNCTOR OVER DEGENERATIONS OF VARIETIES ATOSHI CHOWDHURY Contents 1. Introduction 1 1.1. Overview of problem 1 1.2. Background and context 2 1.3. Outline of paper 3 1.4.
More informationON A THEOREM OF CAMPANA AND PĂUN
ON A THEOREM OF CAMPANA AND PĂUN CHRISTIAN SCHNELL Abstract. Let X be a smooth projective variety over the complex numbers, and X a reduced divisor with normal crossings. We present a slightly simplified
More informationFourier Mukai transforms II Orlov s criterion
Fourier Mukai transforms II Orlov s criterion Gregor Bruns 07.01.2015 1 Orlov s criterion In this note we re going to rely heavily on the projection formula, discussed earlier in Rostislav s talk) and
More informationSingularities of hypersurfaces and theta divisors
Singularities of hypersurfaces and theta divisors Gregor Bruns 09.06.2015 These notes are completely based on the book [Laz04] and the course notes [Laz09] and contain no original thought whatsoever by
More informationChern classes à la Grothendieck
Chern classes à la Grothendieck Theo Raedschelders October 16, 2014 Abstract In this note we introduce Chern classes based on Grothendieck s 1958 paper [4]. His approach is completely formal and he deduces
More informationarxiv: v1 [math.ag] 1 Mar 2017
BIRATIONAL GEOMETRY OF THE MODULI SPACE OF PURE SHEAVES ON QUADRIC SURFACE KIRYONG CHUNG AND HAN-BOM MOON arxiv:1703.00230v1 [math.ag] 1 Mar 2017 ABSTRACT. We study birational geometry of the moduli space
More informationProjections of Veronese surface and morphisms from projective plane to Grassmannian
Proc. Indian Acad. Sci. (Math. Sci.) Vol. 127, No. 1, February 2017, pp. 59 67. DOI 10.1007/s12044-016-0303-6 Projections of Veronese surface and morphisms from projective plane to Grassmannian A EL MAZOUNI
More informationRIMS-1743 K3 SURFACES OF GENUS SIXTEEN. Shigeru MUKAI. February 2012 RESEARCH INSTITUTE FOR MATHEMATICAL SCIENCES. KYOTO UNIVERSITY, Kyoto, Japan
RIMS-1743 K3 SURFACES OF GENUS SIXTEEN By Shigeru MUKAI February 2012 RESEARCH INSTITUTE FOR MATHEMATICAL SCIENCES KYOTO UNIVERSITY, Kyoto, Japan K3 SURFACES OF GENUS SIXTEEN SHIGERU MUKAI Abstract. The
More informationALGEBRAIC GEOMETRY I, FALL 2016.
ALGEBRAIC GEOMETRY I, FALL 2016. DIVISORS. 1. Weil and Cartier divisors Let X be an algebraic variety. Define a Weil divisor on X as a formal (finite) linear combination of irreducible subvarieties of
More informationINTERSECTION THEORY CLASS 6
INTERSECTION THEORY CLASS 6 RAVI VAKIL CONTENTS 1. Divisors 2 1.1. Crash course in Cartier divisors and invertible sheaves (aka line bundles) 3 1.2. Pseudo-divisors 3 2. Intersecting with divisors 4 2.1.
More informationarxiv: v1 [math.ag] 16 Aug 2017
AN EFFECTIVE DIVISOR IN M g DEFINED BY RAMIFICATION CONDITIONS Gabriel Muñoz Abstract arxiv:1708.05086v1 [math.ag] 16 Aug 2017 We define an effective divisor of the moduli space of stable curves M g, which
More informationAnother proof of the global F -regularity of Schubert varieties
Another proof of the global F -regularity of Schubert varieties Mitsuyasu Hashimoto Abstract Recently, Lauritzen, Raben-Pedersen and Thomsen proved that Schubert varieties are globally F -regular. We give
More informationCharacteristic classes in the Chow ring
arxiv:alg-geom/9412008v1 10 Dec 1994 Characteristic classes in the Chow ring Dan Edidin and William Graham Department of Mathematics University of Chicago Chicago IL 60637 Let G be a reductive algebraic
More informationA SHORT PROOF OF ROST NILPOTENCE VIA REFINED CORRESPONDENCES
A SHORT PROOF OF ROST NILPOTENCE VIA REFINED CORRESPONDENCES PATRICK BROSNAN Abstract. I generalize the standard notion of the composition g f of correspondences f : X Y and g : Y Z to the case that X
More information1 Existence of the Néron model
Néron models Setting: S a Dedekind domain, K its field of fractions, A/K an abelian variety. A model of A/S is a flat, separable S-scheme of finite type X with X K = A. The nicest possible model over S
More informationBott vanishing for algebraic surfaces
Bott vanishing for algebraic surfaces Burt Totaro For William Fulton on his eightieth birthday A smooth projective variety X over a field is said to satisfy Bott vanishing if H j (X, Ω i X L) = 0 for all
More informationBoundary of Cohen-Macaulay cone and asymptotic behavior of system of ideals
Boundary of Cohen-Macaulay cone and asymptotic behavior of system of ideals Kazuhiko Kurano Meiji University 1 Introduction On a smooth projective variety, we can define the intersection number for a given
More informationDIVISOR CLASSES AND THE VIRTUAL CANONICAL BUNDLE FOR GENUS 0 MAPS
DIVISOR CLASSES AND THE VIRTUAL CANONICAL BUNDLE FOR GENUS 0 MAPS A. J. DE JONG AND JASON STARR Abstract. We prove divisor class relations for families of genus 0 curves and used them to compute the divisor
More informationh : P 2[n] P 2(n). The morphism h is birational and gives a crepant desingularization of the symmetric product P 2(n).
THE MINIMAL MODEL PROGRAM FOR THE HILBERT SCHEME OF POINTS ON P AND BRIDGELAND STABILITY IZZET COSKUN 1. Introduction This is joint work with Daniele Arcara, Aaron Bertram and Jack Huizenga. I will describe
More informationGAUSSIAN MAPS OF PLANE CURVES WITH NINE SINGULAR POINTS. Dedicated with gratitude to the memory of Sacha Lascu
GAUSSIAN MAPS OF PLANE CURVES WITH NINE SINGULAR POINTS EDOARDO SERNESI Dedicated with gratitude to the memory of Sacha Lascu Abstract. We consider nonsingular curves which are the normalization of plane
More informationthe complete linear series of D. Notice that D = PH 0 (X; O X (D)). Given any subvectorspace V H 0 (X; O X (D)) there is a rational map given by V : X
2. Preliminaries 2.1. Divisors and line bundles. Let X be an irreducible complex variety of dimension n. The group of k-cycles on X is Z k (X) = fz linear combinations of subvarieties of dimension kg:
More informationProjective Images of Kummer Surfaces
Appeared in: Math. Ann. 299, 155-170 (1994) Projective Images of Kummer Surfaces Th. Bauer April 29, 1993 0. Introduction The aim of this note is to study the linear systems defined by the even resp. odd
More informationSTABLE BASE LOCUS DECOMPOSITIONS OF KONTSEVICH MODULI SPACES
STABLE BASE LOCUS DECOMPOSITIONS OF KONTSEVICH MODULI SPACES DAWEI CHEN AND IZZET COSKUN Abstract. In this paper, we determine the stable base locus decomposition of the Kontsevich moduli spaces of degree
More informationarxiv:alg-geom/ v1 21 Mar 1996
AN INTERSECTION NUMBER FOR THE PUNCTUAL HILBERT SCHEME OF A SURFACE arxiv:alg-geom/960305v 2 Mar 996 GEIR ELLINGSRUD AND STEIN ARILD STRØMME. Introduction Let S be a smooth projective surface over an algebraically
More informationVERY STABLE BUNDLES AND PROPERNESS OF THE HITCHIN MAP
VERY STABLE BUNDLES AND PROPERNESS OF THE HITCHIN MAP CHRISTIAN PAULY AND ANA PEÓN-NIETO Abstract. Let X be a smooth complex projective curve of genus g 2 and let K be its canonical bundle. In this note
More informationHolomorphic line bundles
Chapter 2 Holomorphic line bundles In the absence of non-constant holomorphic functions X! C on a compact complex manifold, we turn to the next best thing, holomorphic sections of line bundles (i.e., rank
More informationON VARIETIES OF MAXIMAL ALBANESE DIMENSION
ON VARIETIES OF MAXIMAL ALBANESE DIMENSION ZHI JIANG A smooth projective complex variety X has maximal Albanese dimension if its Albanese map X Alb(X) is generically finite onto its image. These varieties
More informationBRILL-NOETHER THEOREMS AND GLOBALLY GENERATED VECTOR BUNDLES ON HIRZEBRUCH SURFACES
BRILL-NOETHER THEOREMS AND GLOBALLY GENERATED VECTOR BUNDLES ON HIRZEBRUCH SURFACES IZZET COSKUN AND JACK HUIZENGA Abstract. In this paper, we show that the cohomology of a general stable bundle on a Hirzebruch
More informationThe Pfaffian-Grassmannian derived equivalence
The Pfaffian-Grassmannian derived equivalence Lev Borisov, Andrei Căldăraru Abstract We argue that there exists a derived equivalence between Calabi-Yau threefolds obtained by taking dual hyperplane sections
More informationSEPARABLE RATIONAL CONNECTEDNESS AND STABILITY
SEPARABLE RATIONAL CONNECTEDNESS AND STABILIT ZHIU TIAN Abstract. In this short note we prove that in many cases the failure of a variety to be separably rationally connected is caused by the instability
More informationSTABLE BASE LOCUS DECOMPOSITIONS OF KONTSEVICH MODULI SPACES
STABLE BASE LOCUS DECOMPOSITIONS OF KONTSEVICH MODULI SPACES DAWEI CHEN AND IZZET COSKUN Contents 1. Introduction 1 2. Preliminary definitions and background 3 3. Degree two maps to Grassmannians 4 4.
More informationA RECONSTRUCTION THEOREM IN QUANTUM COHOMOLOGY AND QUANTUM K-THEORY
A RECONSTRUCTION THEOREM IN QUANTUM COHOMOLOGY AND QUANTUM K-THEORY Y.-P. LEE AND R. PANDHARIPANDE Abstract. A reconstruction theorem for genus 0 gravitational quantum cohomology and quantum K-theory is
More informationMINIMAL MODELS FOR ELLIPTIC CURVES
MINIMAL MODELS FOR ELLIPTIC CURVES BRIAN CONRAD 1. Introduction In the 1960 s, the efforts of many mathematicians (Kodaira, Néron, Raynaud, Tate, Lichtenbaum, Shafarevich, Lipman, and Deligne-Mumford)
More informationON THE INTERSECTION THEORY OF QUOT SCHEMES AND MODULI OF BUNDLES WITH SECTIONS
ON THE INTERSECTION THEORY OF QUOT SCHEMES AND MODULI OF BUNDLES WITH SECTIONS ALINA MARIAN Abstract. We consider a class of tautological top intersection products on the moduli space of stable pairs consisting
More informationDedicated to Mel Hochster on his 65th birthday. 1. Introduction
GLOBAL DIVISION OF COHOMOLOGY CLASSES VIA INJECTIVITY LAWRENCE EIN AND MIHNEA POPA Dedicated to Mel Hochster on his 65th birthday 1. Introduction The aim of this note is to remark that the injectivity
More informationHodge Theory of Maps
Hodge Theory of Maps Migliorini and de Cataldo June 24, 2010 1 Migliorini 1 - Hodge Theory of Maps The existence of a Kähler form give strong topological constraints via Hodge theory. Can we get similar
More informationIn a series of papers that N. Mohan Kumar and M.P. Murthy ([MK2], [Mu1], [MKM]) wrote, the final theorem was the following.
EULER CYCLES SATYA MANDAL I will talk on the following three papers: (1) A Riemann-Roch Theorem ([DM1]), (2) Euler Class Construction ([DM2]) (3) Torsion Euler Cycle ([BDM]) In a series of papers that
More informationMODULI OF MATHEMATICAL INSTANTON VECTOR BUNDLES WITH ODD c 2 ON PROJECTIVE SPACE
Dedicated to the memory of Andrei Nikolaevich Tyurin MODULI OF MATHEMATICAL INSTANTON VECTOR BUNDLES WITH ODD c 2 ON PROJECTIVE SPACE ALEXANDER S. TIKHOMIROV 1. Introduction By a mathematical n-instanton
More informationMaterial for a series of talks at the ICTP, Trieste, 2000
POSITIVITY OF DIRECT IMAGE SHEAVES AND APPLICATIONS TO FAMILIES OF HIGHER DIMENSIONAL MANIFOLDS ECKART VIEHWEG Material for a series of talks at the ICTP, Trieste, 2000 Let Y be a projective algebraic
More informationTHE MOTIVE OF THE FANO SURFACE OF LINES. 1. Introduction
THE MOTIVE OF THE FANO SURFACE OF LINES HUMBERTO A. DIAZ Abstract. The purpose of this note is to prove that the motive of the Fano surface of lines on a smooth cubic threefold is finite-dimensional in
More informationMODULAR COMPACTIFICATIONS OF THE SPACE OF POINTED ELLIPTIC CURVES I
MODULAR COMPACTIFICATIONS OF THE SPACE OF POINTED ELLIPTIC CURVES I DAVID ISHII SMYTH Abstract. We introduce a sequence of isolated curve singularities, the elliptic m-fold points, and an associated sequence
More informationLINKED ALTERNATING FORMS AND LINKED SYMPLECTIC GRASSMANNIANS
LINKED ALTERNATING FORMS AND LINKED SYMPLECTIC GRASSMANNIANS BRIAN OSSERMAN AND MONTSERRAT TEIXIDOR I BIGAS Abstract. Motivated by applications to higher-rank Brill-Noether theory and the Bertram-Feinberg-Mukai
More informationCoherent sheaves on elliptic curves.
Coherent sheaves on elliptic curves. Aleksei Pakharev April 5, 2017 Abstract We describe the abelian category of coherent sheaves on an elliptic curve, and construct an action of a central extension of
More informationVector bundles in Algebraic Geometry Enrique Arrondo. 1. The notion of vector bundle
Vector bundles in Algebraic Geometry Enrique Arrondo Notes(* prepared for the First Summer School on Complex Geometry (Villarrica, Chile 7-9 December 2010 1 The notion of vector bundle In affine geometry,
More informationSome Remarks on Prill s Problem
AFFINE ALGEBRAIC GEOMETRY pp. 287 292 Some Remarks on Prill s Problem Abstract. N. Mohan Kumar If f : X Y is a non-constant map of smooth curves over C and if there is a degree two map π : X C where C
More informationarxiv: v1 [math.ag] 30 Apr 2018
QUASI-LOG CANONICAL PAIRS ARE DU BOIS OSAMU FUJINO AND HAIDONG LIU arxiv:1804.11138v1 [math.ag] 30 Apr 2018 Abstract. We prove that every quasi-log canonical pair has only Du Bois singularities. Note that
More informationMODULI OF VECTOR BUNDLES ON CURVES AND GENERALIZED THETA DIVISORS
MODULI OF VECTOR BUNDLES ON CURVES AND GENERALIZED THETA DIVISORS MIHNEA POPA 1. Lecture II: Moduli spaces and generalized theta divisors 1.1. The moduli space. Back to the boundedness problem: we want
More informationThe Riemann-Roch Theorem
The Riemann-Roch Theorem TIFR Mumbai, India Paul Baum Penn State 7 August, 2015 Five lectures: 1. Dirac operator 2. Atiyah-Singer revisited 3. What is K-homology? 4. Beyond ellipticity 5. The Riemann-Roch
More informationarxiv:math/ v1 [math.ag] 17 Oct 2006
Remark on a conjecture of Mukai Arnaud BEAUVILLE Introduction arxiv:math/0610516v1 [math.ag] 17 Oct 2006 The conjecture mentioned in the title appears actually as a question in [M] (Problem 4.11): Conjecture.
More informationAn Abel map to the compactified Picard scheme realizes Poincaré duality
An Abel map to the compactified Picard scheme realizes Poincaré duality JESSE LEO KASS KIRSTEN WICKELGREN For a smooth algebraic curve X over a field, applying H 1 to the Abel map X Pic X/ X to the Picard
More informationON THE ISOMORPHISM BETWEEN THE DUALIZING SHEAF AND THE CANONICAL SHEAF
ON THE ISOMORPHISM BETWEEN THE DUALIZING SHEAF AND THE CANONICAL SHEAF MATTHEW H. BAKER AND JÁNOS A. CSIRIK Abstract. We give a new proof of the isomorphism between the dualizing sheaf and the canonical
More informationSome remarks on symmetric correspondences
Some remarks on symmetric correspondences H. Lange Mathematisches Institut Universitat Erlangen-Nurnberg Bismarckstr. 1 1 2 D-91054 Erlangen (Germany) E. Sernesi Dipartimento di Matematica Università Roma
More information3. Lecture 3. Y Z[1/p]Hom (Sch/k) (Y, X).
3. Lecture 3 3.1. Freely generate qfh-sheaves. We recall that if F is a homotopy invariant presheaf with transfers in the sense of the last lecture, then we have a well defined pairing F(X) H 0 (X/S) F(S)
More information7. Classification of Surfaces The key to the classification of surfaces is the behaviour of the canonical
7. Classification of Surfaces The key to the classification of surfaces is the behaviour of the canonical divisor. Definition 7.1. We say that a smooth projective surface is minimal if K S is nef. Warning:
More informationCOUNTING ELLIPTIC PLANE CURVES
PROCEEDINGS OF THE AMERICAN MATHEMATICAL SOCIETY Volume 125, Number 12, December 1997, Pages 3471 3479 S 0002-9939(97)04136-1 COUNTING ELLIPTIC PLANE CURVES WITH FIXED j-invariant RAHUL PANDHARIPANDE (Communicated
More informationALGEBRAIC CYCLES ON THE FANO VARIETY OF LINES OF A CUBIC FOURFOLD arxiv: v2 [math.ag] 18 Apr INTRODUCTION
ALGEBRAIC CYCLES ON THE FANO VARIETY OF LINES OF A CUBIC FOURFOLD arxiv:1609.05627v2 [math.ag] 18 Apr 2018 KALYAN BANERJEE ABSTRACT. In this text we prove that if a smooth cubic in P 5 has its Fano variety
More informationRepresentations and Linear Actions
Representations and Linear Actions Definition 0.1. Let G be an S-group. A representation of G is a morphism of S-groups φ G GL(n, S) for some n. We say φ is faithful if it is a monomorphism (in the category
More informationarxiv: v1 [math.ag] 15 Apr 2013
ON ISOLATED LOG CANONICAL CENTERS arxiv:1304.4173v1 [math.ag] 15 Apr 2013 CHIH-CHI CHOU Abstract. In this paper, we show that the depth of an isolated log canonical center is determined by the cohomology
More informationOrdinary Flops. CHIN-LUNG WANG (NCU and NCTS) (Joint work with H.-W. Lin)
Ordinary Flops CHIN-LUNG WANG (NCU and NCTS) (Joint work with H.-W. Lin) September 6, 2004 CONTENTS 1. Ordinary flips/flops and local models 2. Chow motives and Poincaré pairing 3. Ordinary/quantum product
More informationThe Cone Theorem. Stefano Filipazzi. February 10, 2016
The Cone Theorem Stefano Filipazzi February 10, 2016 These notes are supposed to be a handout for the student seminar in algebraic geometry at the University of Utah. In this seminar, we will give an overview
More informationarxiv: v1 [math.ag] 14 Mar 2019
ASYMPTOTIC CONSTRUCTIONS AND INVARIANTS OF GRADED LINEAR SERIES ariv:1903.05967v1 [math.ag] 14 Mar 2019 CHIH-WEI CHANG AND SHIN-YAO JOW Abstract. Let be a complete variety of dimension n over an algebraically
More informationarxiv:math/ v1 [math.ag] 18 Oct 2003
Proc. Indian Acad. Sci. (Math. Sci.) Vol. 113, No. 2, May 2003, pp. 139 152. Printed in India The Jacobian of a nonorientable Klein surface arxiv:math/0310288v1 [math.ag] 18 Oct 2003 PABLO ARÉS-GASTESI
More information