Arithmetic and physics of Higgs moduli spaces

Transcription

1 Arithmetic and physics of Higgs moduli spaces Tamás Hausel IST Austria Geometry working seminar March, 2017

2 Diffeomorphic spaces in non-abelian Hodge theory C genus g curve; fix group GL n M d Dol := M d B := {A 1, B 1,.., A g, B g GL n moduli space of semistable rank n degree d Higgs bundles (E, φ) φ H 0 (C, End(E) K) Higgs field g i=1 A 1 i B 1 i A i B i = e 2πid n Id}/PGLn when (d, n) = 1 these are smooth non-compact varieties Non-Abelian Hodge Theorem: M d diff M d Dol B (Hitchin, Donaldson, Corlette, Simpson) g = 1 Stone-von Neumann M d B (C ) 2 T Jac(C) M d Dol Problem: what is Poincaré polynomial P(M d Dol ; t) = P(Md B ; t)?

3 Mixed Hodge polynomials (Deligne 1971) proved the existence of W 0 W i W 2k = H k (X; Q) for any complex algebraic variety X H(X; q, t) = dim(w i /W i 1 (H k (X)))t k q i 2, mixed Hodge polynomial P(X; t) = H(X; 1, t), Poincaré polynomial E(X; q) = q d H(1/q, 1), E-polynomial of X. Theorem (Katz 2008) If M is a smooth quasi-projective variety defined over Z and #{M(F q )} = E(q) is a polynomial in q, then E(M; q) = E(q).

4 Mixed Hodge polynomials (Hausel-Villegas 2008) calculates E(M d B ; q) = Md B (F q) = χ Irr(GL n (F q )) GL n (F q ) 2g 2 χ(ξn d ) χ(1) 2g 2 χ(1) E(M d B ; q) = E(Md B ; q) when (d, n) = (d, n) = 1 M d B and Md B Galois conjugate H(Md B ; q, t) = H(Md B ; q, t) Conjecture (Hausel-Villegas, 2008) (z 2l+1 w 2a+1 ) 2g λ (z 2l+2 w 2a )(z 2l w 2a+2 ) T λ = exp n,k H(M d B ;w2k, (zw) 2k )(zw) dn (z 2k 1)(1 w 2k ) T nk k when g = 1 M d B = (C ) 2 by Stone-von Neumann HV (z 2l+1 w 2a+1 ) 2 λ (z 2l+2 w 2a )(z 2l w 2a+2 ) T λ (z = exp k w k ) 2 (z 2k 1)(1 w 2k )(1 T k ) k 1 T k k

5 Sketch of approach by [Chuang Diaconescu Pan 2010] study moduli spaces of ADHM sheaves on C ADHM sheaf: (E, φ 1, φ 2, s 1, s 2 ); a rank r vector bundle E Higgs fields φ 1 H 0 (End(E)), φ 2 H 0 (End(E) K) sections s 1 H 0 (E), s 2 H 0 (E K) satisfying [φ 1, φ 2 ] = s1 s2 there is a stability condition depending on δ R some refined Donaldson-Thomas invariants of the moduli spaces for given δ-stability condition gives polynomials A δ (t) A ± computed by (conjectural) geometric engineering wall-crossing formula for A δc + A δc contains the Poincaré polynomials of lower rank Higgs moduli spaces recursive formula for P t (M r,d Dol ) [Mozgovoy 2011] proved that the recursion is only solved by the conjectured P t (M r,d ) provided the conjectured formula for Dol H(M d,r B ) is a polynomial this integrality is proved by [Mellit 2016] [Maulik-Pixton 2016< ] announce rigorous proofs of the CDP program our conjecture for P t (M r,d ) should be true! Dol

6 Curious Hard Lefschetz (Hausel-Villegas 2008) calculates E(M d B ; q) = Md B (F q) = χ Irr(GL n (F q )) GL n (F q ) 2g 2 χ(ξn d ) χ(1) 2g 2 χ(1) we find E(M d B ; q) = qd n E(M d B ; 1/q) palindromic by Alvis-Curtis duality q n(n 1) 2 χ(1)(1/q) = χ (1)(q) for dual pair χ, χ Irr(GL n (F q )) Curious Hard Lefschetz Conjecture (theorem when n = 2): L l : Gr W d n 2l (Hi l (M d B )) GrW d n +2l Hi+l (M d B ) x x α l, where α W 4 H 2 (M d B ) The implied functional equation on the conjectured H(M d B ; q, t) = (qt)d n H(M d B ; 1 qt 2, t) holds

7 Perverse filtration f : X Y a proper map between complex algebraic varieties of relative dimension d (de Cataldo-Migliorini 2005) introduce perverse filtration P 0 P i... P k (X) H k (X) from the study of the Beilinson-Bernstein-Deligne-Gabber decomposition theorem for Rf (Q X ) into perverse sheaves recipe (de Cataldo-Migliorini, 2008) for perverse filtration when X smooth and Y affine: take Y 0 Y i... Y d = Y s.t. Y i generic with dim(y i ) = i then P k i 1 H k (X) = ker(h k (X) H k (f 1 (Y i ))) the Relative Hard Lefschetz Theorem holds: L l : Gr P d l (H (X)) Gr P d+l H +2l (X) x x α l where α H 2 (X) is a relative ample class

8 Main conjecture recall Hitchin map χ : Md Dol A := n i=1 H0 (C; K i ) (E, φ) charpol(φ) (Hitchin 1987) completely integrable Hamiltonian system and proper Conjecture ( P=W, de Cataldo-Hausel-Migliorini 2008) P k (M d Dol ) W 2k (M d B ) under the isomorphism H (M d Dol ) H (M d B ) from non-abelian Hodge theory. In particular CHL RHL Theorem (de Cataldo-Hausel-Migliorini 2010) P = W for n = 2. proof mirroring Ngô s proof of the fundamental lemma evidence for n > 2?

9 Refined Gopakumar-Vafa conjecture for local curves we follow (Chuang-Diaconescu-Pan 2011) Y total space of O C K C over C Y CY 3-fold, local curve conjectural quantum Pandharipande-Thomas invariants Z ref PT := β H 2 (Y) n Z T β q e E virt (P(Y, β, e); y) Gopakumar-Vafa generating function of refined BPS invariants: F ref GV := T kβ k ( 1)j L +l N (j L,l) (q kj L + +q kj L )q k y l β k 1 β H 2 (Y) j L, l 0 (1 (qy) k )(1 (q/y) k ) Conjecture ( refined BPS, Chuang-Diaconescu-Pan 2011) Z ref PT = exp ( ) F ref GV

10 F ref GV via Relative Hard Lefschetz Gopakumar-Vafa s BPS invariants N j L,j R β heuristically arise from decomposing the cohomology H (M e β ) of the space of D-branes via a putative action of (sl 2 ) L (sl 2 ) R for local curve Y, (Chuang-Diaconescu-Pan 2011) argue that M e β Md where β = n[c] and d = e + n(g 1) Dol recall χ : M d Dol A induces perverse filtration P on H (M d Dol ) with RHL RHL on Gr P (H (M d Dol )) (sl 2) L action on Gr P (H (M d Dol )) the corresponding primitive decomposition H m (M d Dol ) i,jq i,j;m gives at least a (gl 1 ) R action Chuang-Diaconescu-Pan define N j L ;l β := dim(q j L,0;l )

11 Z ref PT via geometric engineering λ geometric engineering Z ref PT = Z gauge Z gauge partition function of certain gauge theory Chuang-Diaconescu-Pan argue that it should be a U(1)-gauge theory on X = R 4 C 2 Z gauge = k 0 Q k χ T2 y ( det(vk ) 1 g (T X [k] ) g) V k is the tautological bundle on the Hilbert scheme X [k] T 2 acts on X and so on X [k] with isolated fixed points Z gauge is defined by localizing to the fixed points after changes of variables we have g.e. Z gauge = Z ref CDP = exp(f PT GV ) P=W (z 2l+1 w 2a+1 ) 2g (z 2l+2 w 2a )(z 2l w 2a+2 ) T λ HV = exp n,k conclusion: HV, CDP + g.e. P = W H(M d B ;w2k, (zw) 2k )(zw) dn (z 2k 1)(1 w 2k ) T nk k

12 g = 1 via geometric engineering when g = 1 M d B = (C ) 2 by Stone-von Neumann HV (z 2l+1 w 2a+1 ) 2 λ (z 2l+2 w 2a )(z 2l w 2a+2 ) T λ (z = exp k w k ) 2 (z 2k 1)(1 w 2k )(1 T k ) k 1 after geometric engineering this formula becomes χ T2 y (X [n] )T n = χ T2 y,st (X n /S n )T n n (Waelder, 2008) proves geometrically a more general DMVV formula for equivariant elliptic genus our g = 1 formula follows! recently [Carlsson, Villegas 2016] and [Rains, Warnaar 2016] found alternative proofs of this g = 1 formula using Nekrasov Okounkov formalism n T k k

13 Mathematical outlook (Chuang-Diaconescu-Pan 2011) refined BPS conjecture (Hausel-Villegas 2008) conjecture on H(M d B ; q, t) provided P = W of (de Cataldo-Hausel-Migliorini 2010) studying wall-crossing for the stability condition for Z ref (Y) PT recursive formulas (Chuang-Diaconescu-Pan 2010) for P t (M d ) studied by (Mozgovoy 2011) Dol mathematically geometric engineering proposes a deep connection between K T 2((C 2 ) [n] ) and H (M d Dol ) may lead to connections between (Haiman 2002) and (Hausel-Letellier-Villegas 2008) explaining the appearance of Macdonald polynomials in both DAHA acts on K T 2((C 2 ) [n] ) by (Gordon-Stafford 2004) it is expected that DAHA acts on H (M d Dol ) from (Yun 2009) are these DAHA actions related by geometric engineering?