KnizhnikZamolodchikov functor for degenerate double affine Hecke - - PowerPoint PPT Presentation

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KnizhnikZamolodchikov functor for degenerate double affine Hecke - - PowerPoint PPT Presentation

RDAHAs dDAHAs Algebraic KZ KnizhnikZamolodchikov functor for degenerate double affine Hecke algebras Wille Liu Universit de Paris 30 June 2020 RDAHAs dDAHAs Algebraic KZ Plan 1 RDAHAs KZ equations RDAHAs KZ functor 2 dDAHAs AKZ


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SLIDE 1

RDAHAs dDAHAs Algebraic KZ

Knizhnik–Zamolodchikov functor for degenerate double affine Hecke algebras

Wille Liu

Université de Paris

30 June 2020

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SLIDE 2

RDAHAs dDAHAs Algebraic KZ

Plan

1 RDAHAs

KZ equations RDAHAs KZ functor

2 dDAHAs

AKZ equations dDAHAs KZ functor Issues

3 Algebraic KZ

Another presentation Blocks of O and block algebras Block algebra Generalisation

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SLIDE 3

Recall rational DAHAs !

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RDAHAs dDAHAs Algebraic KZ

KZ equations for Sn

Sn : symmetric group on n elements, M f.d. CSn-module

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RDAHAs dDAHAs Algebraic KZ

KZ equations for Sn

Sn : symmetric group on n elements, M f.d. CSn-module Knizhnik–Zamolodchikov (KZ) equations for M are the following PDEs for f with values in M : ∂ ∂zi f − h

i−1

  • k=1

1 − si,k zi − zk f + h

n

  • k=i+1

1 − si,k zi − zk f = 0, i ∈ [1, n] (∗) h ∈ C : parameter

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SLIDE 6

RDAHAs dDAHAs Algebraic KZ

KZ equations for Sn

Sn : symmetric group on n elements, M f.d. CSn-module Knizhnik–Zamolodchikov (KZ) equations for M are the following PDEs for f with values in M : ∂ ∂zi f − h

i−1

  • k=1

1 − si,k zi − zk f + h

n

  • k=i+1

1 − si,k zi − zk f = 0, i ∈ [1, n] (∗) h ∈ C : parameter (∗)

Schur–Weyl

= = = = = = = ⇒ KZ equations for GLm on P1 (WZW conformal blocks).

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SLIDE 7

RDAHAs dDAHAs Algebraic KZ

KZ equations for root systems

hR : euclidean vector space, ∆ ⊂ h∗

R reduced root system,

Π ⊂ ∆ base, ∆+ ⊂ ∆ positive roots, h = hR ⊗R C

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SLIDE 8

RDAHAs dDAHAs Algebraic KZ

KZ equations for root systems

hR : euclidean vector space, ∆ ⊂ h∗

R reduced root system,

Π ⊂ ∆ base, ∆+ ⊂ ∆ positive roots, h = hR ⊗R C W : Weyl group of ∆, M : f.d. CW-module

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SLIDE 9

RDAHAs dDAHAs Algebraic KZ

KZ equations for root systems

hR : euclidean vector space, ∆ ⊂ h∗

R reduced root system,

Π ⊂ ∆ base, ∆+ ⊂ ∆ positive roots, h = hR ⊗R C W : Weyl group of ∆, M : f.d. CW-module KZ equations Knizhnik–Zamolodchikov (KZ) equations are the following PDEs for analytic functions f : h∗ → M ∂ξ(f) −

  • α∈∆+

hαξ, α∨1 − sα α∨ f = 0, ξ ∈ h∗ (∗∗) sα ∈ W : reflection w.r.t. α, α∨ ∈ h : dual root of α, hα ∈ C : parameters

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RDAHAs dDAHAs Algebraic KZ

RDAHAs : definition

KZ equations : ∂ξ(f) −

  • α∈∆+

hαξ, α∨1 − sα α∨ f = 0, ξ ∈ h∗

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SLIDE 11

RDAHAs dDAHAs Algebraic KZ

RDAHAs : definition

KZ equations : ∂ξ(f) −

  • α∈∆+

hαξ, α∨1 − sα α∨ f = 0, ξ ∈ h∗ Regular part : h∗

  • = {ξ ∈ h∗ ; ξ, α∨ = 0, ∀α ∈ ∆} ⊂ h∗
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SLIDE 12

RDAHAs dDAHAs Algebraic KZ

RDAHAs : definition

KZ equations : ∂ξ(f) −

  • α∈∆+

hαξ, α∨1 − sα α∨ f = 0, ξ ∈ h∗ Regular part : h∗

  • = {ξ ∈ h∗ ; ξ, α∨ = 0, ∀α ∈ ∆} ⊂ h∗

D(h∗

  • ) : ring of algebraic differential operators on the affine

variety h∗

  • , acted on by W
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SLIDE 13

RDAHAs dDAHAs Algebraic KZ

RDAHAs : definition

KZ equations : ∂ξ(f) −

  • α∈∆+

hαξ, α∨1 − sα α∨ f = 0, ξ ∈ h∗ Regular part : h∗

  • = {ξ ∈ h∗ ; ξ, α∨ = 0, ∀α ∈ ∆} ⊂ h∗

D(h∗

  • ) : ring of algebraic differential operators on the affine

variety h∗

  • , acted on by W

Dunkl operator Dξ ∈ D(h∗

  • ) ⋊ CW for ξ ∈ h∗ :

Dξ := ∂ξ −

  • α∈∆+

hαξ, α∨(α∨)−1(1 − sα) The rational double affine Hecke algebra (RDAHA), is the subalgebra Hrat ⊂ D(h∗

  • ) ⋊ CW generated by C[h∗],CW

and Dξ for ξ ∈ h∗.

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RDAHAs dDAHAs Algebraic KZ

RDAHAs : structure

Dunkl operators : Dξ := ∂ξ −

  • α∈∆+

hαξ, α∨(α∨)−1(1 − sα) ∈ D(h∗

  • ) ⋊ CW
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SLIDE 15

RDAHAs dDAHAs Algebraic KZ

RDAHAs : structure

Dunkl operators : Dξ := ∂ξ −

  • α∈∆+

hαξ, α∨(α∨)−1(1 − sα) ∈ D(h∗

  • ) ⋊ CW

[Dξ, Dξ′] = 0, ∀ξ, ξ′ ∈ h∗. They generate a subalgebra C[h] = Sym h∗ ⊂ Hrat.

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RDAHAs dDAHAs Algebraic KZ

RDAHAs : structure

Dunkl operators : Dξ := ∂ξ −

  • α∈∆+

hαξ, α∨(α∨)−1(1 − sα) ∈ D(h∗

  • ) ⋊ CW

[Dξ, Dξ′] = 0, ∀ξ, ξ′ ∈ h∗. They generate a subalgebra C[h] = Sym h∗ ⊂ Hrat. Triangular decomposition Hrat = C[h∗] ⊗ CW ⊗ C[h]

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RDAHAs dDAHAs Algebraic KZ

KZ functor for RDAHAs : definition

Isomorphism C[h∗

  • ] ⊗C[h∗] Hrat ∼

= D(h∗

  • ) ⋊ CW =: Hrat
  • (∗)
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SLIDE 18

RDAHAs dDAHAs Algebraic KZ

KZ functor for RDAHAs : definition

Isomorphism C[h∗

  • ] ⊗C[h∗] Hrat ∼

= D(h∗

  • ) ⋊ CW =: Hrat
  • (∗)

Given M : coherent Hrat-module

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SLIDE 19

RDAHAs dDAHAs Algebraic KZ

KZ functor for RDAHAs : definition

Isomorphism C[h∗

  • ] ⊗C[h∗] Hrat ∼

= D(h∗

  • ) ⋊ CW =: Hrat
  • (∗)

Given M : coherent Hrat-module M◦ := Hrat

  • ⊗Hrat M : coherent Hrat
  • -module
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SLIDE 20

RDAHAs dDAHAs Algebraic KZ

KZ functor for RDAHAs : definition

Isomorphism C[h∗

  • ] ⊗C[h∗] Hrat ∼

= D(h∗

  • ) ⋊ CW =: Hrat
  • (∗)

Given M : coherent Hrat-module M◦ := Hrat

  • ⊗Hrat M : coherent Hrat
  • -module

Via (∗), M◦ is W-equivariant coherent D(h∗

  • )-module
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RDAHAs dDAHAs Algebraic KZ

KZ functor for RDAHAs : definition

Isomorphism C[h∗

  • ] ⊗C[h∗] Hrat ∼

= D(h∗

  • ) ⋊ CW =: Hrat
  • (∗)

Given M : coherent Hrat-module M◦ := Hrat

  • ⊗Hrat M : coherent Hrat
  • -module

Via (∗), M◦ is W-equivariant coherent D(h∗

  • )-module

Suppose Dξ acts locally nilpotently on M for ξ ∈ h∗.

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RDAHAs dDAHAs Algebraic KZ

KZ functor for RDAHAs : definition

Isomorphism C[h∗

  • ] ⊗C[h∗] Hrat ∼

= D(h∗

  • ) ⋊ CW =: Hrat
  • (∗)

Given M : coherent Hrat-module M◦ := Hrat

  • ⊗Hrat M : coherent Hrat
  • -module

Via (∗), M◦ is W-equivariant coherent D(h∗

  • )-module

Suppose Dξ acts locally nilpotently on M for ξ ∈ h∗.

M◦ is a W-equivariant local system on h∗

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RDAHAs dDAHAs Algebraic KZ

KZ functor for RDAHAs : definition

Isomorphism C[h∗

  • ] ⊗C[h∗] Hrat ∼

= D(h∗

  • ) ⋊ CW =: Hrat
  • (∗)

Given M : coherent Hrat-module M◦ := Hrat

  • ⊗Hrat M : coherent Hrat
  • -module

Via (∗), M◦ is W-equivariant coherent D(h∗

  • )-module

Suppose Dξ acts locally nilpotently on M for ξ ∈ h∗.

M◦ is a W-equivariant local system on h∗

  • flat sections of M◦ form a π1 (h∗
  • /W)-module, denoted M ∇
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RDAHAs dDAHAs Algebraic KZ

KZ functor for RDAHAs : definition

Isomorphism C[h∗

  • ] ⊗C[h∗] Hrat ∼

= D(h∗

  • ) ⋊ CW =: Hrat
  • (∗)

Given M : coherent Hrat-module M◦ := Hrat

  • ⊗Hrat M : coherent Hrat
  • -module

Via (∗), M◦ is W-equivariant coherent D(h∗

  • )-module

Suppose Dξ acts locally nilpotently on M for ξ ∈ h∗.

M◦ is a W-equivariant local system on h∗

  • flat sections of M◦ form a π1 (h∗
  • /W)-module, denoted M ∇

π1 (h∗

  • /W) ∼

= BW , braid group of W

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RDAHAs dDAHAs Algebraic KZ

KZ functor for RDAHAs : definition

Isomorphism C[h∗

  • ] ⊗C[h∗] Hrat ∼

= D(h∗

  • ) ⋊ CW =: Hrat
  • (∗)

Given M : coherent Hrat-module M◦ := Hrat

  • ⊗Hrat M : coherent Hrat
  • -module

Via (∗), M◦ is W-equivariant coherent D(h∗

  • )-module

Suppose Dξ acts locally nilpotently on M for ξ ∈ h∗.

M◦ is a W-equivariant local system on h∗

  • flat sections of M◦ form a π1 (h∗
  • /W)-module, denoted M ∇

π1 (h∗

  • /W) ∼

= BW , braid group of W BW -action on M ∇ factorises through HW , Iwahori–Hecke algebra of W

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RDAHAs dDAHAs Algebraic KZ

KZ functor for RDAHAs : definition (cont.)

O(Hrat) : category of coherent Hrat-modules on which Dξ acts locally nilpotently for ξ ∈ h∗

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RDAHAs dDAHAs Algebraic KZ

KZ functor for RDAHAs : definition (cont.)

O(Hrat) : category of coherent Hrat-modules on which Dξ acts locally nilpotently for ξ ∈ h∗ KZ functor [Guay–Ginzburg–Opdam–Rouquier ’03] The KZ functor V : O(Hrat) → HW -mod is defined by the assignement O(Hrat) ∋ M → M∇ ∈ HW -mod .

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RDAHAs dDAHAs Algebraic KZ

KZ functor for RDAHAs : definition (cont.)

O(Hrat) : category of coherent Hrat-modules on which Dξ acts locally nilpotently for ξ ∈ h∗ KZ functor [Guay–Ginzburg–Opdam–Rouquier ’03] The KZ functor V : O(Hrat) → HW -mod is defined by the assignement O(Hrat) ∋ M → M∇ ∈ HW -mod . Recall the Iwahori–Hecke algebra HW is

generated by Tα for simple roots α ∈ Π

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RDAHAs dDAHAs Algebraic KZ

KZ functor for RDAHAs : definition (cont.)

O(Hrat) : category of coherent Hrat-modules on which Dξ acts locally nilpotently for ξ ∈ h∗ KZ functor [Guay–Ginzburg–Opdam–Rouquier ’03] The KZ functor V : O(Hrat) → HW -mod is defined by the assignement O(Hrat) ∋ M → M∇ ∈ HW -mod . Recall the Iwahori–Hecke algebra HW is

generated by Tα for simple roots α ∈ Π modulo the braid relations TαTβTα · · · = TβTαTβ · · ·

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RDAHAs dDAHAs Algebraic KZ

KZ functor for RDAHAs : definition (cont.)

O(Hrat) : category of coherent Hrat-modules on which Dξ acts locally nilpotently for ξ ∈ h∗ KZ functor [Guay–Ginzburg–Opdam–Rouquier ’03] The KZ functor V : O(Hrat) → HW -mod is defined by the assignement O(Hrat) ∋ M → M∇ ∈ HW -mod . Recall the Iwahori–Hecke algebra HW is

generated by Tα for simple roots α ∈ Π modulo the braid relations TαTβTα · · · = TβTαTβ · · · and the quadratic relations (Tα − vα)(Tα + v−1

α ) = 0

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RDAHAs dDAHAs Algebraic KZ

KZ functor for RDAHAs : definition (cont.)

O(Hrat) : category of coherent Hrat-modules on which Dξ acts locally nilpotently for ξ ∈ h∗ KZ functor [Guay–Ginzburg–Opdam–Rouquier ’03] The KZ functor V : O(Hrat) → HW -mod is defined by the assignement O(Hrat) ∋ M → M∇ ∈ HW -mod . Recall the Iwahori–Hecke algebra HW is

generated by Tα for simple roots α ∈ Π modulo the braid relations TαTβTα · · · = TβTαTβ · · · and the quadratic relations (Tα − vα)(Tα + v−1

α ) = 0

Parameters are given by vα = exp(π√−1hα)

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RDAHAs dDAHAs Algebraic KZ

KZ functor for RDAHAs : properties

KZ functor V : O(Hrat) → HW -mod V(M) = M∇ Theorem [Guay–Ginzburg–Opdam–Rouquier ’03]

1 O(Hrat) is a highest weight category with index set

Irrep(W)

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RDAHAs dDAHAs Algebraic KZ

KZ functor for RDAHAs : properties

KZ functor V : O(Hrat) → HW -mod V(M) = M∇ Theorem [Guay–Ginzburg–Opdam–Rouquier ’03]

1 O(Hrat) is a highest weight category with index set

Irrep(W)

2 V is a quotient functor of abelian categories, inducing

equivalence O(Hrat)/ ker V ∼ = HW -mod

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RDAHAs dDAHAs Algebraic KZ

KZ functor for RDAHAs : properties

KZ functor V : O(Hrat) → HW -mod V(M) = M∇ Theorem [Guay–Ginzburg–Opdam–Rouquier ’03]

1 O(Hrat) is a highest weight category with index set

Irrep(W)

2 V is a quotient functor of abelian categories, inducing

equivalence O(Hrat)/ ker V ∼ = HW -mod

3 V satisfies the double centraliser property, i.e. V is fully

faithful on projective objects of O(Hrat)

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RDAHAs dDAHAs Algebraic KZ

KZ functor for RDAHAs : properties

KZ functor V : O(Hrat) → HW -mod V(M) = M∇ Theorem [Guay–Ginzburg–Opdam–Rouquier ’03]

1 O(Hrat) is a highest weight category with index set

Irrep(W)

2 V is a quotient functor of abelian categories, inducing

equivalence O(Hrat)/ ker V ∼ = HW -mod

3 V satisfies the double centraliser property, i.e. V is fully

faithful on projective objects of O(Hrat)

4 L ∈ O(Hrat) : simple module,

PL ∈ O(Hrat) : projective cover of L. Then L ∈ ker V ⇔ PL is not injective

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RDAHAs dDAHAs Algebraic KZ

Example : SL2

hR = R · ϵ, ∆ = {±α}, α, ϵ = 1, W = s ; s2 = e.

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RDAHAs dDAHAs Algebraic KZ

Example : SL2

hR = R · ϵ, ∆ = {±α}, α, ϵ = 1, W = s ; s2 = e. KZ : d dz f − h1 − s z f = 0

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RDAHAs dDAHAs Algebraic KZ

Example : SL2

hR = R · ϵ, ∆ = {±α}, α, ϵ = 1, W = s ; s2 = e. KZ : d dz f − h1 − s z f = 0 Dunkl : D = d

dz − hz−1(1 − s)

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RDAHAs dDAHAs Algebraic KZ

Example : SL2

hR = R · ϵ, ∆ = {±α}, α, ϵ = 1, W = s ; s2 = e. KZ : d dz f − h1 − s z f = 0 Dunkl : D = d

dz − hz−1(1 − s)

RDAHA : Hrat = Cz, s, D / (sz = −zs, sD = −Ds, [D, z] = 1 − 2hs).

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RDAHAs dDAHAs Algebraic KZ

Example : SL2

hR = R · ϵ, ∆ = {±α}, α, ϵ = 1, W = s ; s2 = e. KZ : d dz f − h1 − s z f = 0 Dunkl : D = d

dz − hz−1(1 − s)

RDAHA : Hrat = Cz, s, D / (sz = −zs, sD = −Ds, [D, z] = 1 − 2hs). Iwahori–Hecke HW = C[T]/(T − v)(T + v−1), v = exp(π√−1h). T = monodromy of half-turn around 0 ∈ C.

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RDAHAs dDAHAs Algebraic KZ

Example : SL2

RDAHA : Hrat = Cz, s, D / (sz = −zs, sD = −Ds, [D, z] = 1 − 2hs). Iwahori–Hecke HW = C[T]/(T − v)(T + v−1), v = exp(π√−1h). T = monodromy of half-turn around 0 ∈ C. Consider h = 1/2. Then Hrat has a one-dimensional module

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SLIDE 42

RDAHAs dDAHAs Algebraic KZ

Example : SL2

RDAHA : Hrat = Cz, s, D / (sz = −zs, sD = −Ds, [D, z] = 1 − 2hs). Iwahori–Hecke HW = C[T]/(T − v)(T + v−1), v = exp(π√−1h). T = monodromy of half-turn around 0 ∈ C. Consider h = 1/2. Then Hrat has a one-dimensional module Ltriv = C · u0.

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RDAHAs dDAHAs Algebraic KZ

Example : SL2

RDAHA : Hrat = Cz, s, D / (sz = −zs, sD = −Ds, [D, z] = 1 − 2hs). Iwahori–Hecke HW = C[T]/(T − v)(T + v−1), v = exp(π√−1h). T = monodromy of half-turn around 0 ∈ C. Consider h = 1/2. Then Hrat has a one-dimensional module Ltriv = C · u0. zu0 = Du0 = 0, su0 = u0.

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SLIDE 44

RDAHAs dDAHAs Algebraic KZ

Example : SL2

RDAHA : Hrat = Cz, s, D / (sz = −zs, sD = −Ds, [D, z] = 1 − 2hs). Iwahori–Hecke HW = C[T]/(T − v)(T + v−1), v = exp(π√−1h). T = monodromy of half-turn around 0 ∈ C. Consider h = 1/2. Then Hrat has a one-dimensional module Ltriv = C · u0. zu0 = Du0 = 0, su0 = u0. In this case,

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SLIDE 45

RDAHAs dDAHAs Algebraic KZ

Example : SL2

RDAHA : Hrat = Cz, s, D / (sz = −zs, sD = −Ds, [D, z] = 1 − 2hs). Iwahori–Hecke HW = C[T]/(T − v)(T + v−1), v = exp(π√−1h). T = monodromy of half-turn around 0 ∈ C. Consider h = 1/2. Then Hrat has a one-dimensional module Ltriv = C · u0. zu0 = Du0 = 0, su0 = u0. In this case, v = exp(π√−1h) = √−1

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RDAHAs dDAHAs Algebraic KZ

Example : SL2

RDAHA : Hrat = Cz, s, D / (sz = −zs, sD = −Ds, [D, z] = 1 − 2hs). Iwahori–Hecke HW = C[T]/(T − v)(T + v−1), v = exp(π√−1h). T = monodromy of half-turn around 0 ∈ C. Consider h = 1/2. Then Hrat has a one-dimensional module Ltriv = C · u0. zu0 = Du0 = 0, su0 = u0. In this case, v = exp(π√−1h) = √−1 HW = C[T]/(T − √−1)2

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RDAHAs dDAHAs Algebraic KZ

Example : SL2

RDAHA : Hrat = Cz, s, D / (sz = −zs, sD = −Ds, [D, z] = 1 − 2hs). Iwahori–Hecke HW = C[T]/(T − v)(T + v−1), v = exp(π√−1h). T = monodromy of half-turn around 0 ∈ C. Consider h = 1/2. Then Hrat has a one-dimensional module Ltriv = C · u0. zu0 = Du0 = 0, su0 = u0. In this case, v = exp(π√−1h) = √−1 HW = C[T]/(T − √−1)2 ker V = Ltriv.

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Recall (trigonometrically) degenerate DAHAs !

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RDAHAs dDAHAs Algebraic KZ

AKZ equations for Hgr−aff

n

Hgr−aff

n

: graded affine Hecke algebra for GLn,

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RDAHAs dDAHAs Algebraic KZ

AKZ equations for Hgr−aff

n

Hgr−aff

n

: graded affine Hecke algebra for GLn,

generated by subalgebras C[x1, · · · , xn] and CSn

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SLIDE 51

RDAHAs dDAHAs Algebraic KZ

AKZ equations for Hgr−aff

n

Hgr−aff

n

: graded affine Hecke algebra for GLn,

generated by subalgebras C[x1, · · · , xn] and CSn modulo relations : [si, xj] = 0 for j / ∈ {i, i + 1}, sixi − xi+1si = h and sixi+1 − xisi = −h.

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RDAHAs dDAHAs Algebraic KZ

AKZ equations for Hgr−aff

n

Hgr−aff

n

: graded affine Hecke algebra for GLn,

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SLIDE 53

RDAHAs dDAHAs Algebraic KZ

AKZ equations for Hgr−aff

n

Hgr−aff

n

: graded affine Hecke algebra for GLn, M f.d. Hgr−aff

n

  • module
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RDAHAs dDAHAs Algebraic KZ

AKZ equations for Hgr−aff

n

Hgr−aff

n

: graded affine Hecke algebra for GLn, M f.d. Hgr−aff

n

  • module

Affine Knizhnik–Zamolodchikov (AKZ) equations for M are the following PDEs for f with values in M : zi ∂ ∂zi f + xi · f − h

i−1

  • k=1

1 − si,k 1 − zk/zi f (∗) − h

n

  • k=i+1

1 − si,k 1 − zi/zk f − hρ, ω∨

i = 0,

i ∈ [1, n] h ∈ C : parameter

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SLIDE 55

RDAHAs dDAHAs Algebraic KZ

AKZ equations for Hgr−aff

n

Hgr−aff

n

: graded affine Hecke algebra for GLn, M f.d. Hgr−aff

n

  • module

Affine Knizhnik–Zamolodchikov (AKZ) equations for M are the following PDEs for f with values in M : zi ∂ ∂zi f + xi · f − h

i−1

  • k=1

1 − si,k 1 − zk/zi f (∗) − h

n

  • k=i+1

1 − si,k 1 − zi/zk f − hρ, ω∨

i = 0,

i ∈ [1, n] h ∈ C : parameter (∗)

Schur–Weyl

= = = = = = = ⇒ KZ equations for GLm on P1 (WZW conformal blocks).

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RDAHAs dDAHAs Algebraic KZ

AKZ equations for root systems

∆ ⊂ h∗

R reduced root system as above,

P ⊂ h∗

R weight

lattice, Q∨ = Z∆∨ dual root lattice, h = hR ⊗R C

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SLIDE 57

RDAHAs dDAHAs Algebraic KZ

AKZ equations for root systems

∆ ⊂ h∗

R reduced root system as above,

P ⊂ h∗

R weight

lattice, Q∨ = Z∆∨ dual root lattice, h = hR ⊗R C T ∨ = P ⊗ C× dual torus, C[T ∨] = C[zµ ; µ ∈ Q∨]

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RDAHAs dDAHAs Algebraic KZ

AKZ equations for root systems

∆ ⊂ h∗

R reduced root system as above,

P ⊂ h∗

R weight

lattice, Q∨ = Z∆∨ dual root lattice, h = hR ⊗R C T ∨ = P ⊗ C× dual torus, C[T ∨] = C[zµ ; µ ∈ Q∨] W : Weyl group of ∆, Hgr−aff : graded affine Hecke algebra for ∆, M : f.d. Hgr−aff-module

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SLIDE 59

RDAHAs dDAHAs Algebraic KZ

AKZ equations for root systems

∆ ⊂ h∗

R reduced root system as above,

P ⊂ h∗

R weight

lattice, Q∨ = Z∆∨ dual root lattice, h = hR ⊗R C T ∨ = P ⊗ C× dual torus, C[T ∨] = C[zµ ; µ ∈ Q∨] W : Weyl group of ∆, Hgr−aff : graded affine Hecke algebra for ∆, M : f.d. Hgr−aff-module AKZ equations Affine Knizhnik–Zamolodchikov (AKZ) equations are the following PDEs for analytic functions f : T ∨ → M ∂ξ(f) + ξ · f −

  • α∈∆+

hαξ, α∨ 1 − sα 1 − z−α∨ f − ξ, ρ∨

h f = 0

for ξ ∈ h∗. hα ∈ C : parameters, ρ∨

h = (1/2) α∈∆+ hαα∨

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SLIDE 60

RDAHAs dDAHAs Algebraic KZ

dDAHAs : definition

AKZ equations : ∂ξ(f) + ξ · f −

  • α∈∆+

hαξ, α∨ 1 − sα 1 − z−α∨ f − ξ, ρ∨

h f = 0

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SLIDE 61

RDAHAs dDAHAs Algebraic KZ

dDAHAs : definition

AKZ equations : ∂ξ(f) + ξ · f −

  • α∈∆+

hαξ, α∨ 1 − sα 1 − z−α∨ f − ξ, ρ∨

h f = 0

Regular part : T ∨

  • =
  • z ∈ T ∨ ; zα∨ = 1, ∀α ∈ ∆
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SLIDE 62

RDAHAs dDAHAs Algebraic KZ

dDAHAs : definition

AKZ equations : ∂ξ(f) + ξ · f −

  • α∈∆+

hαξ, α∨ 1 − sα 1 − z−α∨ f − ξ, ρ∨

h f = 0

Regular part : T ∨

  • =
  • z ∈ T ∨ ; zα∨ = 1, ∀α ∈ ∆
  • D(T ∨
  • ) : ring of algebraic differential operators on the affine

variety T ∨

  • , acted on by W
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SLIDE 63

RDAHAs dDAHAs Algebraic KZ

dDAHAs : definition

AKZ equations : ∂ξ(f) + ξ · f −

  • α∈∆+

hαξ, α∨ 1 − sα 1 − z−α∨ f − ξ, ρ∨

h f = 0

Regular part : T ∨

  • =
  • z ∈ T ∨ ; zα∨ = 1, ∀α ∈ ∆
  • D(T ∨
  • ) : ring of algebraic differential operators on the affine

variety T ∨

  • , acted on by W

Dunkl operator Dξ ∈ D(T ∨

  • ) ⋊ CW for ξ ∈ h∗ :

Dξ := ∂ξ −

  • α∈∆+

hαξ, α∨(1 − z−α∨)−1(1 − sα) + ξ, ρ∨

h

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SLIDE 64

RDAHAs dDAHAs Algebraic KZ

dDAHAs : definition

AKZ equations : ∂ξ(f) + ξ · f −

  • α∈∆+

hαξ, α∨ 1 − sα 1 − z−α∨ f − ξ, ρ∨

h f = 0

Regular part : T ∨

  • =
  • z ∈ T ∨ ; zα∨ = 1, ∀α ∈ ∆
  • D(T ∨
  • ) : ring of algebraic differential operators on the affine

variety T ∨

  • , acted on by W

Dunkl operator Dξ ∈ D(T ∨

  • ) ⋊ CW for ξ ∈ h∗ :

Dξ := ∂ξ −

  • α∈∆+

hαξ, α∨(1 − z−α∨)−1(1 − sα) + ξ, ρ∨

h

The degenerate double affine Hecke algebra (dDAHA), is the subalgebra Htrig ⊂ D(T ∨

  • ) ⋊ CW generated by

C[T ∨],CW and Dξ for ξ ∈ h∗.

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SLIDE 65

RDAHAs dDAHAs Algebraic KZ

dDAHAs : structure

Dunkl operator : Dξ := ∂ξ−

  • α∈∆+

hαξ, α∨(1−z−α∨)−1(1−sα)+ξ, ρ∨

h ∈ D(T ∨

  • )⋊CW
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SLIDE 66

RDAHAs dDAHAs Algebraic KZ

dDAHAs : structure

Dunkl operator : Dξ := ∂ξ−

  • α∈∆+

hαξ, α∨(1−z−α∨)−1(1−sα)+ξ, ρ∨

h ∈ D(T ∨

  • )⋊CW

[Dξ, Dξ′] = 0, ∀ξ, ξ′ ∈ h∗. They generate a subalgebra C[h] = Sym h∗ ⊂ Htrig.

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SLIDE 67

RDAHAs dDAHAs Algebraic KZ

dDAHAs : structure

Dunkl operator : Dξ := ∂ξ−

  • α∈∆+

hαξ, α∨(1−z−α∨)−1(1−sα)+ξ, ρ∨

h ∈ D(T ∨

  • )⋊CW

[Dξ, Dξ′] = 0, ∀ξ, ξ′ ∈ h∗. They generate a subalgebra C[h] = Sym h∗ ⊂ Htrig. There is a subalgebra Hgr−aff ∼ = CW ⊗ C[h] ⊂ Htrig

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SLIDE 68

RDAHAs dDAHAs Algebraic KZ

dDAHAs : structure

Dunkl operator : Dξ := ∂ξ−

  • α∈∆+

hαξ, α∨(1−z−α∨)−1(1−sα)+ξ, ρ∨

h ∈ D(T ∨

  • )⋊CW

[Dξ, Dξ′] = 0, ∀ξ, ξ′ ∈ h∗. They generate a subalgebra C[h] = Sym h∗ ⊂ Htrig. There is a subalgebra Hgr−aff ∼ = CW ⊗ C[h] ⊂ Htrig Triangular decomposition Htrig = C[T ∨] ⊗ CW ⊗ C[h]

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SLIDE 69

RDAHAs dDAHAs Algebraic KZ

KZ functor for dDAHAs : definition

Isomorphism C[T ∨

  • ] ⊗C[T ∨] Htrig ∼

= D(T ∨

  • ) ⋊ CW =: Htrig
  • (∗)
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SLIDE 70

RDAHAs dDAHAs Algebraic KZ

KZ functor for dDAHAs : definition

Isomorphism C[T ∨

  • ] ⊗C[T ∨] Htrig ∼

= D(T ∨

  • ) ⋊ CW =: Htrig
  • (∗)

Given M : coherent Htrig-module

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SLIDE 71

RDAHAs dDAHAs Algebraic KZ

KZ functor for dDAHAs : definition

Isomorphism C[T ∨

  • ] ⊗C[T ∨] Htrig ∼

= D(T ∨

  • ) ⋊ CW =: Htrig
  • (∗)

Given M : coherent Htrig-module M◦ := Htrig

  • ⊗Htrig M : coherent Htrig
  • module
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SLIDE 72

RDAHAs dDAHAs Algebraic KZ

KZ functor for dDAHAs : definition

Isomorphism C[T ∨

  • ] ⊗C[T ∨] Htrig ∼

= D(T ∨

  • ) ⋊ CW =: Htrig
  • (∗)

Given M : coherent Htrig-module M◦ := Htrig

  • ⊗Htrig M : coherent Htrig
  • module

Via (∗), M◦ is W-equivariant coherent D(T ∨

  • )-module
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SLIDE 73

RDAHAs dDAHAs Algebraic KZ

KZ functor for dDAHAs : definition

Isomorphism C[T ∨

  • ] ⊗C[T ∨] Htrig ∼

= D(T ∨

  • ) ⋊ CW =: Htrig
  • (∗)

Given M : coherent Htrig-module M◦ := Htrig

  • ⊗Htrig M : coherent Htrig
  • module

Via (∗), M◦ is W-equivariant coherent D(T ∨

  • )-module

Suppose Dξ acts locally finitely on M for ξ ∈ h∗.

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SLIDE 74

RDAHAs dDAHAs Algebraic KZ

KZ functor for dDAHAs : definition

Isomorphism C[T ∨

  • ] ⊗C[T ∨] Htrig ∼

= D(T ∨

  • ) ⋊ CW =: Htrig
  • (∗)

Given M : coherent Htrig-module M◦ := Htrig

  • ⊗Htrig M : coherent Htrig
  • module

Via (∗), M◦ is W-equivariant coherent D(T ∨

  • )-module

Suppose Dξ acts locally finitely on M for ξ ∈ h∗.

M◦ is a W-equivariant local system on T ∨

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SLIDE 75

RDAHAs dDAHAs Algebraic KZ

KZ functor for dDAHAs : definition

Isomorphism C[T ∨

  • ] ⊗C[T ∨] Htrig ∼

= D(T ∨

  • ) ⋊ CW =: Htrig
  • (∗)

Given M : coherent Htrig-module M◦ := Htrig

  • ⊗Htrig M : coherent Htrig
  • module

Via (∗), M◦ is W-equivariant coherent D(T ∨

  • )-module

Suppose Dξ acts locally finitely on M for ξ ∈ h∗.

M◦ is a W-equivariant local system on T ∨

  • flat sections of M◦ form a π1 ([T ∨
  • /W])-module, denoted

M ∇

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SLIDE 76

RDAHAs dDAHAs Algebraic KZ

KZ functor for dDAHAs : definition

Isomorphism C[T ∨

  • ] ⊗C[T ∨] Htrig ∼

= D(T ∨

  • ) ⋊ CW =: Htrig
  • (∗)

Given M : coherent Htrig-module M◦ := Htrig

  • ⊗Htrig M : coherent Htrig
  • module

Via (∗), M◦ is W-equivariant coherent D(T ∨

  • )-module

Suppose Dξ acts locally finitely on M for ξ ∈ h∗.

M◦ is a W-equivariant local system on T ∨

  • flat sections of M◦ form a π1 ([T ∨
  • /W])-module, denoted

M ∇

  • rbifold fundamental group π1 ([T ∨
  • /W]) ∼

= ˜ BW , (extended) affine braid group

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SLIDE 77

RDAHAs dDAHAs Algebraic KZ

KZ functor for dDAHAs : definition

Isomorphism C[T ∨

  • ] ⊗C[T ∨] Htrig ∼

= D(T ∨

  • ) ⋊ CW =: Htrig
  • (∗)

Given M : coherent Htrig-module M◦ := Htrig

  • ⊗Htrig M : coherent Htrig
  • module

Via (∗), M◦ is W-equivariant coherent D(T ∨

  • )-module

Suppose Dξ acts locally finitely on M for ξ ∈ h∗.

M◦ is a W-equivariant local system on T ∨

  • flat sections of M◦ form a π1 ([T ∨
  • /W])-module, denoted

M ∇

  • rbifold fundamental group π1 ([T ∨
  • /W]) ∼

= ˜ BW , (extended) affine braid group ˜ BW -action on M ∇ factorises through Haff, (extended) affine Hecke algebra for ∆

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SLIDE 78

RDAHAs dDAHAs Algebraic KZ

KZ functor for dDAHAs : definition (cont.)

O(Htrig) : category of coherent Htrig-modules on which Dξ acts locally finitely for ξ ∈ h∗

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SLIDE 79

RDAHAs dDAHAs Algebraic KZ

KZ functor for dDAHAs : definition (cont.)

O(Htrig) : category of coherent Htrig-modules on which Dξ acts locally finitely for ξ ∈ h∗ O(Haff) : category of f.d. Haff-modules

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SLIDE 80

RDAHAs dDAHAs Algebraic KZ

KZ functor for dDAHAs : definition (cont.)

O(Htrig) : category of coherent Htrig-modules on which Dξ acts locally finitely for ξ ∈ h∗ O(Haff) : category of f.d. Haff-modules KZ functor [Varagnolo–Vasserot ’04] The KZ functor V : O(Htrig) → O(Haff) is defined by the assignement O(Htrig) ∋ M → M∇ ∈ O(Haff).

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SLIDE 81

RDAHAs dDAHAs Algebraic KZ

KZ functor for dDAHAs : definition (cont.)

O(Htrig) : category of coherent Htrig-modules on which Dξ acts locally finitely for ξ ∈ h∗ O(Haff) : category of f.d. Haff-modules KZ functor [Varagnolo–Vasserot ’04] The KZ functor V : O(Htrig) → O(Haff) is defined by the assignement O(Htrig) ∋ M → M∇ ∈ O(Haff). Parameters are given by vα = exp(π√−1hα)

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SLIDE 82

RDAHAs dDAHAs Algebraic KZ

KZ functor for dDAHAs : definition (cont.)

O(Htrig) : category of coherent Htrig-modules on which Dξ acts locally finitely for ξ ∈ h∗ O(Haff) : category of f.d. Haff-modules KZ functor [Varagnolo–Vasserot ’04] The KZ functor V : O(Htrig) → O(Haff) is defined by the assignement O(Htrig) ∋ M → M∇ ∈ O(Haff). Parameters are given by vα = exp(π√−1hα) This also works for non-reduced root systems

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SLIDE 83

RDAHA v.s. dDAHA

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SLIDE 84

RDAHAs dDAHAs Algebraic KZ

Recapitulation

Hrat Htrig

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SLIDE 85

RDAHAs dDAHAs Algebraic KZ

Recapitulation

Hrat Htrig KZ eq ∂ξ(f) −

α hαξ, α∨1−sα α∨ f = 0

∂ξ(f) + ξ · f −

α hαξ, α∨ 1−sα 1−z−α∨ f

+ξ, ρ∨

h f = 0

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SLIDE 86

RDAHAs dDAHAs Algebraic KZ

Recapitulation

Hrat Htrig KZ eq ∂ξ(f) −

α hαξ, α∨1−sα α∨ f = 0

∂ξ(f) + ξ · f −

α hαξ, α∨ 1−sα 1−z−α∨ f

+ξ, ρ∨

h f = 0

coeffs f.d. CW-mod f.d. Hgr−aff-mod

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SLIDE 87

RDAHAs dDAHAs Algebraic KZ

Recapitulation

Hrat Htrig KZ eq ∂ξ(f) −

α hαξ, α∨1−sα α∨ f = 0

∂ξ(f) + ξ · f −

α hαξ, α∨ 1−sα 1−z−α∨ f

+ξ, ρ∨

h f = 0

coeffs f.d. CW-mod f.d. Hgr−aff-mod

  • ver

h∗

  • /W

[T ∨

  • /W]
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SLIDE 88

RDAHAs dDAHAs Algebraic KZ

Recapitulation

Hrat Htrig KZ eq ∂ξ(f) −

α hαξ, α∨1−sα α∨ f = 0

∂ξ(f) + ξ · f −

α hαξ, α∨ 1−sα 1−z−α∨ f

+ξ, ρ∨

h f = 0

coeffs f.d. CW-mod f.d. Hgr−aff-mod

  • ver

h∗

  • /W

[T ∨

  • /W]

mndrmy f.d. HW -mod f.d. Haff-mod

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SLIDE 89

RDAHAs dDAHAs Algebraic KZ

Recapitulation

Hrat Htrig KZ eq ∂ξ(f) −

α hαξ, α∨1−sα α∨ f = 0

∂ξ(f) + ξ · f −

α hαξ, α∨ 1−sα 1−z−α∨ f

+ξ, ρ∨

h f = 0

coeffs f.d. CW-mod f.d. Hgr−aff-mod

  • ver

h∗

  • /W

[T ∨

  • /W]

mndrmy f.d. HW -mod f.d. Haff-mod O h∗-loc. nilp. h∗-loc. fin.

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SLIDE 90

RDAHAs dDAHAs Algebraic KZ

Recapitulation

Hrat Htrig KZ eq ∂ξ(f) −

α hαξ, α∨1−sα α∨ f = 0

∂ξ(f) + ξ · f −

α hαξ, α∨ 1−sα 1−z−α∨ f

+ξ, ρ∨

h f = 0

coeffs f.d. CW-mod f.d. Hgr−aff-mod

  • ver

h∗

  • /W

[T ∨

  • /W]

mndrmy f.d. HW -mod f.d. Haff-mod O h∗-loc. nilp. h∗-loc. fin. V : O(Hrat) → HW -mod O(Htrig) → O(Haff)

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SLIDE 91

Coming back to dDAHAs...

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SLIDE 92

RDAHAs dDAHAs Algebraic KZ

KZ functor for dDAHAs : properties

KZ functor V : O(Htrig) → O(Haff) V(M) = M∇

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SLIDE 93

RDAHAs dDAHAs Algebraic KZ

KZ functor for dDAHAs : properties

KZ functor V : O(Htrig) → O(Haff) V(M) = M∇ Theorem [L.]

1 V is a quotient functor of abelian categories, inducing

equivalence O(Htrig)/ ker V ∼ = O(Haff)

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SLIDE 94

RDAHAs dDAHAs Algebraic KZ

KZ functor for dDAHAs : properties

KZ functor V : O(Htrig) → O(Haff) V(M) = M∇ Theorem [L.]

1 V is a quotient functor of abelian categories, inducing

equivalence O(Htrig)/ ker V ∼ = O(Haff)

2 V satisfies the double centraliser property, i.e. V is fully

faithful on projective objects of O(Htrig)

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SLIDE 95

RDAHAs dDAHAs Algebraic KZ

KZ functor for dDAHAs : properties

KZ functor V : O(Htrig) → O(Haff) V(M) = M∇ Theorem [L.]

1 V is a quotient functor of abelian categories, inducing

equivalence O(Htrig)/ ker V ∼ = O(Haff)

2 V satisfies the double centraliser property, i.e. V is fully

faithful on projective objects of the completion of O(Htrig)

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SLIDE 96

RDAHAs dDAHAs Algebraic KZ

KZ functor for dDAHAs : properties

KZ functor V : O(Htrig) → O(Haff) V(M) = M∇ Theorem [L.]

1 V is a quotient functor of abelian categories, inducing

equivalence O(Htrig)/ ker V ∼ = O(Haff)

2 V satisfies the double centraliser property, i.e. V is fully

faithful on projective objects of the completion of O(Htrig)

3 L ∈ O(Htrig) : simple module,

PL ∈ O(Htrig) : projective cover of L. Then L ∈ ker V ⇔ PL is not injective

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SLIDE 97

RDAHAs dDAHAs Algebraic KZ

KZ functor for dDAHAs : properties

KZ functor V : O(Htrig) → O(Haff) V(M) = M∇ Theorem [L.]

1 V is a quotient functor of abelian categories, inducing

equivalence O(Htrig)/ ker V ∼ = O(Haff)

2 V satisfies the double centraliser property, i.e. V is fully

faithful on projective objects of the completion of O(Htrig)

3 L ∈ O(Htrig) : simple module,

PL ∈ Pro O(Htrig) : projective cover of L. Then L ∈ ker V ⇔ PL is not relatively injective / categorical centre

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SLIDE 98

RDAHAs dDAHAs Algebraic KZ

Example : SL2

hR = R · ϵ, ∆ = {±α}, α, ϵ = 1, W = s ; s2 = e.

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SLIDE 99

RDAHAs dDAHAs Algebraic KZ

Example : SL2

hR = R · ϵ, ∆ = {±α}, α, ϵ = 1, W = s ; s2 = e. P = Z · (α/2), Q∨ = Z · (2ϵ), T ∨ = C[z±2ϵ].

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SLIDE 100

RDAHAs dDAHAs Algebraic KZ

Example : SL2

hR = R · ϵ, ∆ = {±α}, α, ϵ = 1, W = s ; s2 = e. P = Z · (α/2), Q∨ = Z · (2ϵ), T ∨ = C[z±2ϵ]. Let y = z2ϵ. AKZ : y d dyf + α · f − 2h 1 − s 1 − y−1 f − h · f = 0

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SLIDE 101

RDAHAs dDAHAs Algebraic KZ

Example : SL2

hR = R · ϵ, ∆ = {±α}, α, ϵ = 1, W = s ; s2 = e. P = Z · (α/2), Q∨ = Z · (2ϵ), T ∨ = C[z±2ϵ]. Let y = z2ϵ. AKZ : y d dyf + α · f − 2h 1 − s 1 − y−1 f − h · f = 0 Dunkl : D = y d

dy − h(1 − y−1)−1(1 − s) + h/2

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SLIDE 102

RDAHAs dDAHAs Algebraic KZ

Example : SL2

hR = R · ϵ, ∆ = {±α}, α, ϵ = 1, W = s ; s2 = e. P = Z · (α/2), Q∨ = Z · (2ϵ), T ∨ = C[z±2ϵ]. Let y = z2ϵ. AKZ : y d dyf + α · f − 2h 1 − s 1 − y−1 f − h · f = 0 Dunkl : D = y d

dy − h(1 − y−1)−1(1 − s) + h/2

dDAHA : Htrig = Cy, s, D / (sy = y−1s, sD + Ds = h, [D, y] = y − h(y + 1)).

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SLIDE 103

RDAHAs dDAHAs Algebraic KZ

Example : SL2

hR = R · ϵ, ∆ = {±α}, α, ϵ = 1, W = s ; s2 = e. P = Z · (α/2), Q∨ = Z · (2ϵ), T ∨ = C[z±2ϵ]. Let y = z2ϵ. AKZ : y d dyf + α · f − 2h 1 − s 1 − y−1 f − h · f = 0 Dunkl : D = y d

dy − h(1 − y−1)−1(1 − s) + h/2

dDAHA : Htrig = Cy, s, D / (sy = y−1s, sD + Ds = h, [D, y] = y − h(y + 1)). Affine Hecke Haff = CT, X/((T − v)(T + v−1) = 0, TX − X−1T = (v − v−1)X), v = exp(π√−1h). T = monodromy of half-turn around 1 ∈ C, X = monodromy around 0.

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SLIDE 104

RDAHAs dDAHAs Algebraic KZ

Example : SL2

dDAHA : Htrig = Cy, s, D / (sy = y−1s, sD + Ds = h, [D, y] = y − h(y + 1)). Affine Hecke Haff = CT, X/((T − v)(T + v−1) = 0, TX − X−1T = (v − v−1)X), v = exp(π√−1h). T = monodromy of half-turn around 1 ∈ C, X = monodromy around 0. Consider h = 1/2. Then Htrig has a one-dimensional module Ltriv = C · u0.

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SLIDE 105

RDAHAs dDAHAs Algebraic KZ

Example : SL2

dDAHA : Htrig = Cy, s, D / (sy = y−1s, sD + Ds = h, [D, y] = y − h(y + 1)). Affine Hecke Haff = CT, X/((T − v)(T + v−1) = 0, TX − X−1T = (v − v−1)X), v = exp(π√−1h). T = monodromy of half-turn around 1 ∈ C, X = monodromy around 0. Consider h = 1/2. Then Htrig has a one-dimensional module Ltriv = C · u0. yu0 = u0, Du0 = u0/4, su0 = u0.

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SLIDE 106

RDAHAs dDAHAs Algebraic KZ

Example : SL2

dDAHA : Htrig = Cy, s, D / (sy = y−1s, sD + Ds = h, [D, y] = y − h(y + 1)). Affine Hecke Haff = CT, X/((T − v)(T + v−1) = 0, TX − X−1T = (v − v−1)X), v = exp(π√−1h). T = monodromy of half-turn around 1 ∈ C, X = monodromy around 0. Consider h = 1/2. Then Htrig has a one-dimensional module Ltriv = C · u0. yu0 = u0, Du0 = u0/4, su0 = u0. In this case,

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SLIDE 107

RDAHAs dDAHAs Algebraic KZ

Example : SL2

dDAHA : Htrig = Cy, s, D / (sy = y−1s, sD + Ds = h, [D, y] = y − h(y + 1)). Affine Hecke Haff = CT, X/((T − v)(T + v−1) = 0, TX − X−1T = (v − v−1)X), v = exp(π√−1h). T = monodromy of half-turn around 1 ∈ C, X = monodromy around 0. Consider h = 1/2. Then Htrig has a one-dimensional module Ltriv = C · u0. yu0 = u0, Du0 = u0/4, su0 = u0. In this case, v = exp(π√−1h) = √−1

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SLIDE 108

RDAHAs dDAHAs Algebraic KZ

Example : SL2

dDAHA : Htrig = Cy, s, D / (sy = y−1s, sD + Ds = h, [D, y] = y − h(y + 1)). Affine Hecke Haff = CT, X/((T − v)(T + v−1) = 0, TX − X−1T = (v − v−1)X), v = exp(π√−1h). T = monodromy of half-turn around 1 ∈ C, X = monodromy around 0. Consider h = 1/2. Then Htrig has a one-dimensional module Ltriv = C · u0. yu0 = u0, Du0 = u0/4, su0 = u0. In this case, v = exp(π√−1h) = √−1 Haff = CX, T/((T − √−1)2 = 0, TX − X−1T = 2√−1X)

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SLIDE 109

RDAHAs dDAHAs Algebraic KZ

Example : SL2

dDAHA : Htrig = Cy, s, D / (sy = y−1s, sD + Ds = h, [D, y] = y − h(y + 1)). Affine Hecke Haff = CT, X/((T − v)(T + v−1) = 0, TX − X−1T = (v − v−1)X), v = exp(π√−1h). T = monodromy of half-turn around 1 ∈ C, X = monodromy around 0. Consider h = 1/2. Then Htrig has a one-dimensional module Ltriv = C · u0. yu0 = u0, Du0 = u0/4, su0 = u0. In this case, v = exp(π√−1h) = √−1 Haff = CX, T/((T − √−1)2 = 0, TX − X−1T = 2√−1X) ker V = Ltriv.

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Issues

There are several issues :

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Issues

There are several issues : Unlike O(Hrat), we need to complete O(Htrig) to get projective objects.

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Issues

There are several issues : Unlike O(Hrat), we need to complete O(Htrig) to get projective objects. The construction of V is analytic.

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Issues

There are several issues : Unlike O(Hrat), we need to complete O(Htrig) to get projective objects. The construction of V is analytic. The monodromy representation of Haff on M∇ is not easily computable.

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Issues

There are several issues : Unlike O(Hrat), we need to complete O(Htrig) to get projective objects. The construction of V is analytic. The monodromy representation of Haff on M∇ is not easily computable. − → A more algebraic approach to O(Htrig) and V is needed.

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Algebraic approach

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Another presentation of Htrig

Recall triangular decomposition Htrig = C[T ∨] ⊗ CW ⊗ C[h].

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Another presentation of Htrig

Recall triangular decomposition Htrig = C[T ∨] ⊗ CW ⊗ C[h]. We have C[T ∨] = CQ∨ ; Q∨ ⊂ hR : dual root lattice

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Another presentation of Htrig

Recall triangular decomposition Htrig = C[T ∨] ⊗ CW ⊗ C[h]. We have C[T ∨] = CQ∨ ; Q∨ ⊂ hR : dual root lattice C W = C[T ∨] ⊗ CW ⊂ Htrig ;

  • W affine Weyl group
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Another presentation of Htrig

Recall triangular decomposition Htrig = C[T ∨] ⊗ CW ⊗ C[h]. We have C[T ∨] = CQ∨ ; Q∨ ⊂ hR : dual root lattice C W = C[T ∨] ⊗ CW ⊂ Htrig ;

  • W affine Weyl group
  • W = sα ; α ∈

Π ;

  • Π ⊂

∆ base of affine root system

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Another presentation of Htrig

Recall triangular decomposition Htrig = C[T ∨] ⊗ CW ⊗ C[h]. We have C[T ∨] = CQ∨ ; Q∨ ⊂ hR : dual root lattice C W = C[T ∨] ⊗ CW ⊂ Htrig ;

  • W affine Weyl group
  • W = sα ; α ∈

Π ;

  • Π ⊂

∆ base of affine root system

  • W acts properly on hR by affine reflections
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Another presentation of Htrig

Recall triangular decomposition Htrig = C[T ∨] ⊗ CW ⊗ C[h]. We have C[T ∨] = CQ∨ ; Q∨ ⊂ hR : dual root lattice C W = C[T ∨] ⊗ CW ⊂ Htrig ;

  • W affine Weyl group
  • W = sα ; α ∈

Π ;

  • Π ⊂

∆ base of affine root system

  • W acts properly on hR by affine reflections

Another presentation of dDAHA Htrig = C W ⊗ C[h] satisfies the following relations for f ∈ C[h] and α ∈ Π : sα f − sα(f) sα = hα f − sα(f) α .

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Blocks of O(Htrig)

Let M ∈ O(Htrig), so that Dξ acts locally finitely for ξ ∈ h∗

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Blocks of O(Htrig)

Let M ∈ O(Htrig), so that Dξ acts locally finitely for ξ ∈ h∗ M decomposes into generalised eigenspaces of C[h] : M =

  • λ∈h

Mλ, Mλ =

  • ξ∈h∗
  • k≥0
  • x ∈ M ; (Dξ − ξ, λ)kx = 0
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Blocks of O(Htrig)

Let M ∈ O(Htrig), so that Dξ acts locally finitely for ξ ∈ h∗ M decomposes into generalised eigenspaces of C[h] : M =

  • λ∈h

Mλ, Mλ =

  • ξ∈h∗
  • k≥0
  • x ∈ M ; (Dξ − ξ, λ)kx = 0
  • For λ0 ∈ h, let

Wλ0 ⊂ h denote the W-orbit of λ0. Define Oλ0(Htrig) =

  • M ∈ O(Htrig) ; M =
  • λ∈

Wλ0

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Blocks of O(Htrig)

Let M ∈ O(Htrig), so that Dξ acts locally finitely for ξ ∈ h∗ M decomposes into generalised eigenspaces of C[h] : M =

  • λ∈h

Mλ, Mλ =

  • ξ∈h∗
  • k≥0
  • x ∈ M ; (Dξ − ξ, λ)kx = 0
  • For λ0 ∈ h, let

Wλ0 ⊂ h denote the W-orbit of λ0. Define Oλ0(Htrig) =

  • M ∈ O(Htrig) ; M =
  • λ∈

Wλ0

  • Decomposition into blocks :

O(Htrig) =

  • λ0∈h/

W

Oλ0(Htrig).

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Block Oλ0(Htrig)

We want to study the block Oλ0(Htrig) =

  • M ∈ O(Htrig) ; M =
  • λ∈

Wλ0

  • for a fixed λ0 ∈ h.
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Block Oλ0(Htrig)

We want to study the block Oλ0(Htrig) =

  • M ∈ O(Htrig) ; M =
  • λ∈

Wλ0

  • for a fixed λ0 ∈ h.

A result of Rouquier and Brundan–Kleshchev : each block

  • f a graded affine Hecke algebras of type A is equivalent to

a quiver Hecke algebra for the linear quiver

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Block Oλ0(Htrig)

We want to study the block Oλ0(Htrig) =

  • M ∈ O(Htrig) ; M =
  • λ∈

Wλ0

  • for a fixed λ0 ∈ h.

A result of Rouquier and Brundan–Kleshchev : each block

  • f a graded affine Hecke algebras of type A is equivalent to

a quiver Hecke algebra for the linear quiver This result has a double-affine analogue.

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Block Oλ0(Htrig) (cont.)

For a fixed λ0 ∈ h, we want to study the block Oλ0(Htrig) =

  • M ∈ O(Htrig) ; M =
  • λ∈

Wλ0

  • .
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Block Oλ0(Htrig) (cont.)

For a fixed λ0 ∈ h, we want to study the block Oλ0(Htrig) =

  • M ∈ O(Htrig) ; M =
  • λ∈

Wλ0

  • .

There is a non-unital associative algebra Hλ0 generated by

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Block Oλ0(Htrig) (cont.)

For a fixed λ0 ∈ h, we want to study the block Oλ0(Htrig) =

  • M ∈ O(Htrig) ; M =
  • λ∈

Wλ0

  • .

There is a non-unital associative algebra Hλ0 generated by

  • rthogonal idempotents e(λ) ∈ Hλ0 for λ ∈

Wλ0,

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Block Oλ0(Htrig) (cont.)

For a fixed λ0 ∈ h, we want to study the block Oλ0(Htrig) =

  • M ∈ O(Htrig) ; M =
  • λ∈

Wλ0

  • .

There is a non-unital associative algebra Hλ0 generated by

  • rthogonal idempotents e(λ) ∈ Hλ0 for λ ∈

Wλ0, a polynomial subalgebra C[h]e(λ) ⊂ Hλ0 for each λ ∈ Wλ0,

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Block Oλ0(Htrig) (cont.)

For a fixed λ0 ∈ h, we want to study the block Oλ0(Htrig) =

  • M ∈ O(Htrig) ; M =
  • λ∈

Wλ0

  • .

There is a non-unital associative algebra Hλ0 generated by

  • rthogonal idempotents e(λ) ∈ Hλ0 for λ ∈

Wλ0, a polynomial subalgebra C[h]e(λ) ⊂ Hλ0 for each λ ∈ Wλ0, for α ∈ Π, a Hecke operator ταe(λ) = e(sαλ)τα ∈ Hλ0 for each λ ∈ Wλ0.

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Block Oλ0(Htrig) (cont.)

For a fixed λ0 ∈ h, we want to study the block Oλ0(Htrig) =

  • M ∈ O(Htrig) ; M =
  • λ∈

Wλ0

  • .

There is a non-unital associative algebra Hλ0 generated by

  • rthogonal idempotents e(λ) ∈ Hλ0 for λ ∈

Wλ0, a polynomial subalgebra C[h]e(λ) ⊂ Hλ0 for each λ ∈ Wλ0, for α ∈ Π, a Hecke operator ταe(λ) = e(sαλ)τα ∈ Hλ0 for each λ ∈ Wλ0. Hλ0 satisfies relations similar to those of the quiver Hecke algebras (Khovanov–Lauda–Rouquier algebras)

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Block Oλ0(Htrig) (cont.)

Let Hλ0 -mod0 be the category of Hλ0-modules M such that

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Block Oλ0(Htrig) (cont.)

Let Hλ0 -mod0 be the category of Hλ0-modules M such that M =

λ∈ Wλ0 Mλ

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Block Oλ0(Htrig) (cont.)

Let Hλ0 -mod0 be the category of Hλ0-modules M such that M =

λ∈ Wλ0 Mλ

dim Mλ < ∞ for all λ ∈ Wλ0.

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Block Oλ0(Htrig) (cont.)

Let Hλ0 -mod0 be the category of Hλ0-modules M such that M =

λ∈ Wλ0 Mλ

dim Mλ < ∞ for all λ ∈ Wλ0. Generalisation of [Rouquier ’08] and [Brundan–Kleshchev ’09] There is an equivalence of categories Oλ0(Htrig) ∼ = Hλ0 -mod0

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Block Oλ0(Htrig) (cont.)

Let Hλ0 -mod0 be the category of Hλ0-modules M such that M =

λ∈ Wλ0 Mλ

dim Mλ < ∞ for all λ ∈ Wλ0. Generalisation of [Rouquier ’08] and [Brundan–Kleshchev ’09] There is an equivalence of categories Oλ0(Htrig) ∼ = Hλ0 -mod0 Thus Hλ0 is the “block algebra” of Oλ0(Htrig).

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The block algebra Hλ0

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Block algebra Hλ0

Advantages of Hλ0 over Htrig :

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Block algebra Hλ0

Advantages of Hλ0 over Htrig : As Hλ0 has a Z-grading, we can consider its graded modules.

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Block algebra Hλ0

Advantages of Hλ0 over Htrig : As Hλ0 has a Z-grading, we can consider its graded modules. Hλ0 has enough graded projective modules.

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Block algebra Hλ0

Advantages of Hλ0 over Htrig : As Hλ0 has a Z-grading, we can consider its graded modules. Hλ0 has enough graded projective modules. The centre of Hλ0 is a graded polynomial ring.

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Block algebra Hλ0

Advantages of Hλ0 over Htrig : As Hλ0 has a Z-grading, we can consider its graded modules. Hλ0 has enough graded projective modules. The centre of Hλ0 is a graded polynomial ring. Hλ0 has a lot of idempotents.

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Idempotent subalgebra of Hλ0

Similarly, there is a block decomposition for affine Hecke algebras O(Haff) =

  • ℓ0∈T/W

Oℓ0(Haff)

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Idempotent subalgebra of Hλ0

Similarly, there is a block decomposition for affine Hecke algebras O(Haff) =

  • ℓ0∈T/W

Oℓ0(Haff) and a graded algebra Kℓ0 with an equivalence of category Oℓ0(Haff) ∼ = Kℓ0 -mod0 .

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Idempotent subalgebra of Hλ0

Similarly, there is a block decomposition for affine Hecke algebras O(Haff) =

  • ℓ0∈T/W

Oℓ0(Haff) and a graded algebra Kℓ0 with an equivalence of category Oℓ0(Haff) ∼ = Kℓ0 -mod0 . Theorem [L.] There exists an idempotent e ∈ Hλ0 of degree 0 and a graded ring isomorphism eHλ0e ∼ = Kℓ0 with ℓ0 = exp(λ0) ∈ T.

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Algebraic KZ functor

Using the isomorphism eHλ0e ∼ = Kℓ0, we define a functor on ungraded modules V : Hλ0 -mod0 → Kλ0 -mod0, M → eM.

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Algebraic KZ functor

Using the isomorphism eHλ0e ∼ = Kℓ0, we define a functor on ungraded modules V : Hλ0 -mod0 → Kλ0 -mod0, M → eM. Question Does the following diagram commutes ? Oλ0(Htrig) Oℓ0(Haff) Hλ0 -mod0 Kλ0 -mod0

V ∼ = ∼ = V

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Algebraic KZ functor

Using the isomorphism eHλ0e ∼ = Kℓ0, we define a functor on ungraded modules V : Hλ0 -mod0 → Kλ0 -mod0, M → eM. Question Does the following diagram commutes ? Oλ0(Htrig) Oℓ0(Haff) Hλ0 -mod0 Kλ0 -mod0

V ∼ = ∼ = V

Proposition [L.] ker V = ker V

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Generalisation

Hλ0 and Kℓ0 have are defined in a similar way as quiver Hecke algebras

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Generalisation

Hλ0 and Kℓ0 have are defined in a similar way as quiver Hecke algebras The definition can be easily generalised, just as the quiver Hecke algebras are defined for all quivers.

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Generalisation

Hλ0 and Kℓ0 have are defined in a similar way as quiver Hecke algebras The definition can be easily generalised, just as the quiver Hecke algebras are defined for all quivers. The isomorphism eHλ0e ∼ = Kℓ0 generalises.

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Generalisation

Hλ0 and Kℓ0 have are defined in a similar way as quiver Hecke algebras The definition can be easily generalised, just as the quiver Hecke algebras are defined for all quivers. The isomorphism eHλ0e ∼ = Kℓ0 generalises. The KZ functor V : M → eM satisfies the double centraliser property : it is fully faithful on graded projective modules

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Generalisation

Hλ0 and Kℓ0 have are defined in a similar way as quiver Hecke algebras The definition can be easily generalised, just as the quiver Hecke algebras are defined for all quivers. The isomorphism eHλ0e ∼ = Kℓ0 generalises. The KZ functor V : M → eM satisfies the double centraliser property : it is fully faithful on graded projective modules The kernel ker V is characterised as follows : L ∈ Hλ0 -gmod : simple module, PL ∈ Hλ0 -gmod : projective cover of L. Then L ∈ ker V ⇔ PL is not relatively injective over Z(Hλ0)

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FIN