Hopf代数的双交叉积
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391Vol.39,No.1 19961ACTA MATHEMATICA SINICA Jan.,1996Hopf(100083):HopfYang-Baxter Hopf Drinfeld D(H)[8]D(H)S.Majid D(H)Smash S.Majid Smash Smash ()“”Smashk Hopf1HopfHopf Hopf.H Hopf C H Cβ:C→H⊗C;β(c)=Σc(1)⊗c(2),∀c∈C(1)Σc(1)⊗(c(2))1⊗(c(2))2=Σc(1)1c(1)2⊗c(2)1⊗c(2)2;(2)Σc(1)ε(c(2))=ε(c)1;(3)Σε(c(1))c(2)=c.ψ:C→H⊗Hψ(c)=Σc ⊗c ,C⊗H∆(c⊗h)=Σc1⊗c(1)2c 3h1⊗c(2)2⊗c 3h2,ε(c⊗h)=ε(c)ε(h).1.1H Cβ,ψ,∆,ε(C⊗H,∆,ε)β,ψ∀c∈C(i)(1⊗ε)ψ(c)=(ε⊗1)ψ(c)=ε(c)1;(ii)Σc(1)1c 2⊗c(2)(1)1c 2⊗c(2)(2)1=Σc 1c(1)21⊗c 1c(1)22⊗c(2)2;(iii)Σc(1)1c 2⊗c(2)1(c 2)1⊗c(2)1(c 2)2=Σc 1(c 2)1⊗c 1(c 2)2⊗c 2.199365199411281Hopf109(C ⊗H,∆,ε)C β[ψ] H .(C ⊗H,∆,ε)(1⊗ε)∆(c ⊗1)=c ⊗1=(ε⊗1)∆(c ⊗1).ε⊗1(i).(1⊗∆)∆(c ⊗1)=(∆⊗1)∆(c ⊗1),ε⊗1⊗ε⊗1⊗1⊗ε,ε⊗1⊗ε⊗1⊗ε⊗1(ii)(iii).(i),(ii)(iii)∀c ∈C ,h ∈H ,(1⊗∆)∆(c ⊗h )=Σc 1⊗c (1)2c 3h 1⊗∆ c (2)2⊗c3h 2 =Σc 1⊗c (1)2c 3h 1⊗ c (2)2 1⊗ c (2)2 (1)2 c (2)2 3 c3 1h 2⊗ c (2)2 (2)2⊗ c (2)2 3(c 3)2h 3=Σc 1⊗c (1)2c (1)3c 4h 1⊗ c (2)2 1⊗ c (2)2 (1)2 c (2)3 (c 4)1h 2⊗ c (2)2 (2)2⊗ c (2)3 2(c 4)2h 3=Σc 1⊗c (1)2c 3(c4)1h 1⊗ c (2)2 1⊗ c (2)2 (1)2c 3(c 4)2h 2⊗ c (2)2 (2)2⊗c 4h 3=Σc 1⊗c (1)2c (1)3c 4(c5)1h 1⊗c (2)2⊗ c (2)3(1)c 4(c 5)2h 2⊗ c (2)3 (2)⊗c 5h 3=Σc 1⊗c (1)2c 3 c (1)4 1(c 5)1h 1⊗c (2)2⊗c 3 c (1)4 2(c 5)2h 2⊗c (2)4⊗c 5h 3=(∆⊗1)∆(c ⊗h ).(ii)(iii),1.1GkGG“group-like”(∆(g )=g ⊗g,∀g ∈G ).HHopfβ:kG →H ⊗kG ;β(g )=Σg (1)⊗g (2);ψ:G →H ⊗H ;ψ(g )=Σg ⊗g .β,ψkG ⊗H(1)Σg (1)⊗(g (2))1⊗(g (2))2=Σg (1)g (1)⊗g (2)⊗g (2);(2)Σg (1)ε(g (2))=1;(3)Σε(g (1))g (2)=g .(i)(1⊗ε)ψ(g )=(ε⊗1)ψ(g )=1;(ii)Σg (1)g ⊗g (2)(1)g ⊗g (2)(2)=Σg (g (1))1⊗g (g (1))2⊗g (2);(iii)Σg (1)g ⊗(g (2)) (g )1⊗(g (2)) (g )2=Σg (g )1⊗g (g )2⊗g .∆(g ⊗h )=Σg ⊗g (1)g h 1⊗g (2)⊗g h 2,ε(g ⊗h )=ε(h )1.2ψψ(c )=ε(c )(1⊗1),∀c ∈C ,(iii)(ii)CH -C β[ψ] H Smash1.3HCβ(c )=1⊗c ,∀c ∈C ,(ii)Σψ(c 1)⊗c 2=Σψ(c 2)⊗c 1,(i)(iii)∆(c ⊗h )=Σc 1⊗c 3h 1⊗c 2⊗c3h 2.110391.4u∈Hom k(C,H)(convolution)u−1=v.εu=ε,∀c∈Cβ:C→H⊗C;β(c)=Σu(c1)v(c3)⊗c2;ψ:C→H⊗H;ψ(c)=Σ(u(c1)⊗u(c2))∆v(c3).1.1Cβ[ψ] H.u u−1=su,ψ(c)=Σ(u(c1)⊗u(c2))∆su(c3)=ε(c)(1⊗1).1.2Smash C H,C H∼=C⊗H(C⊗H).Φ:C H→C⊗H;Φ(c⊗h)=Σc1⊗v(c2)h,ΦΦ (c⊗h)=Σc1⊗u(c2)h,Φ Φ()ΦC H∼=C⊗H, 1.1Cβ[ψ] H∼=C⊗H.H Cu∈Hom k(C,H)u−1=v,εu=ε,ψ,ϕC H⊗H ψ(c)=Σ(u(c1)⊗u(c2))ϕ(c3)∆v(c4),c∈C,uϕ(c)=Σ(v(c2)⊗v(c1))ψ(c3)∆u(c4).β:C→H⊗Cβ(c)=Σu(c1)v(c3)⊗c2β :C→H⊗C;β (c)=1⊗c1.2H,C,ϕ,ψ,β,β(1)ψ(i)ϕ(i).(2)β,ψ(ii)β ,ϕ(ii).(3)β,ψ(ii),β,ψ(iii)β ,ϕ(iii).(4)Cβ[ψ] H Cβ [ϕ] H Cβ[ψ] H∼= Cβ [ϕ] H.1.21.1H Hopf C u∈Hom k(C,H)u−1,εu=ε.ψ(c)=Σ(u(c1)⊗u(c2))∆u−1(c3),β(c)=Σu(c1)u−1(c3)⊗c2,Cβ[ψ] H∼=C⊗H().1.2ϕ1Hopf1111.2H,C,u1.1,ϕ(c )=Σ u −1(c 2)⊗u −1(c 1)∆u (c 3).C β H ∼=C β[ϕ] H ,C β[ϕ]H ∼=C ⊗Huβ1.2ψψ(c )=ε(c )(1⊗1)2HopfHopfHAHopfSmashH,AHopfHA[6]α,A Hβ,α:A ⊗H →A ;α(a ⊗h )=a ·h,∀a ∈A,h ∈H,β:H →A ⊗H ;β(b )=Σh (1)⊗h (2).ψ:H →A ⊗A ,ψ(h )=Σh ⊗h X :H ⊗H →Aψ(1)=1⊗1,ε(X (h,l ))=ε(h )ε(l ).∀h,l ∈H ,(h ⊗a )(g ⊗b )=Σh 1g 1⊗X (h 2,g 2)(a ·g 3)b,∆(h ⊗a )=Σh 1⊗h (1)2h 3a 1⊗h (2)2⊗h3a 2,ε(h ⊗a )=ε(h )ε(a ).a,b ∈A ,g,h ∈H .(H ⊗A,∆,ε)(H ⊗A,·,1⊗1)(H ⊗A,∆,ε,·,1⊗1)2.1H,AHopfα,β,ψ,X(H ⊗A,∆,ε,·,1⊗1)∀a ∈A ,h,g,k ∈HX (1,h )=X (h,1)=ε(h )1,(a)Σ(a ·(h 1k 1))X (h 2,k 2)=ΣX (h 1,k 1)((a ·h 2)·k 2),(b)ΣX (h 1g 1,k 1)(X (h 2,g 2)·k 2)=ΣX (h,g 1k 1)X (g 2,k 2),(c)(1⊗ε)ψ(h )=(ε⊗1)ψ(h )=ε(h )(1⊗1),(d)Σh (1)1h 2⊗h (2)(1)1h 2⊗h (2)(2)1=Σh 1 h (1)2 1⊗h1 h (1)2 2⊗h (2)2,(e)Σh (1)1h 2⊗ h (2)1 (h 2)1⊗ h (2)1 (h 2)2=Σh 1(h 2)1⊗h 1(h 2)2⊗h2,(f)ε(a ·h )=ε(a )ε(h ),(A1)Σh 1(a ·h 2)1⊗h 1(a ·h 2)2=Σ(a 1·h 1)h (1)2h 3⊗ a 2·h (2)2 h 3,(A2)β(1)=1⊗1,(B1)Σβ(h 1k 1)(X (h 2,k 2)⊗1)=ΣX (h 1,k 1) h (1)2·k 2 k (1)3⊗h (2)2k (2)3,(B2)11239Σh (1)1(a ·h 2)⊗h (2)1=Σ(a ·h 1)h (1)2⊗h (2)2,(C)Σψ(h 1k 1)∆X (h 2,k 2)=ΣX (h 1,k 1) h (1)2·k 2 k (1)3(h 3·k 4)k (1)5k6⊗X h (2)2,k (2)3 h 3·k (2)5 k 6.(D)(H ⊗A,∆,ε,·,1⊗1)H A H β[ψ] α[X ]A .H β[ψ] α[X ]A ε((1⊗a )(g ⊗1))=ε(1⊗a )ε(g ⊗1)(A1),∆(1⊗1)=1⊗1⊗1⊗1(B1).(a),(b)(c)[6]4.6(d),(e)(f)1.1∆((1⊗a )(g ⊗1))=∆(Σg 1⊗(a ·g 2))=Σg 1⊗g (1)2g 3(a ·g 4)1⊗g (2)2⊗g3(a ·g 4)2,∆(1⊗a )∆(g ⊗1)=Σg 1⊗(a 1·g 2)g (1)3g4⊗ g (2)3 1⊗ a 2· g (2)3 2 g 4=Σg 1⊗(a 1·g 2)g (1)3g (1)4g 5⊗g (2)3⊗ a 2·g (2)4 g5.∆((1⊗a )(g ⊗1))=∆(1⊗a )∆(g ⊗1),ε⊗1⊗ε⊗1,ε⊗1⊗1⊗ε(A2),(C).∆((h ⊗1)(g ⊗1)=∆(h ⊗1)∆(g ⊗1),ε⊗1⊗1⊗ε,ε⊗1⊗ε⊗1(C)(B2),(D).(H ⊗A,∆,ε,·,1⊗1)1.1,(H ⊗A,∆,ε)[6]4.6(H ⊗A,·,1⊗1)∆εε((h ⊗a )(g ⊗b ))=ε(Σh 1g 1⊗X (h 2,g 2)(a ·g 3)b )=ε(h 1)·ε(g 1)ε(X (h 2,g 2))ε(a )ε(b )=ε(h ⊗a )ε(g ⊗b ),ε(1⊗1)=ε(1)ε(1)=1,ε.ψ(1)=1⊗1,∆(1⊗1)=1⊗1⊗1⊗1.∆((h ⊗a )(g ⊗b ))=∆(Σh 1g 1⊗X (h 2,g 2)(a ·g 3)b )=Σh 1g 1⊗(h 2g 2)(1)(h 3g 3) (X (h 4,g 4)(a ·g 5)b )1⊗(h 2g 2)(2)⊗(h 3g 3) (X (h 4,g 4)(a ·g 5)b )2=Σh 1g 1⊗(h 2g 2)(1)X (h 3,g 3) h (1)4·g 4 g (1)5(h 5·g 6)g (1)7g 8(a ·g 9)1b 1⊗(h 2g 2)(2)⊗X h (2)4,g (2)5 (h 5·g (2)7g8(a ·g 9)2b 2=Σh 1g 1⊗(h 2g 2)(1)X (h 3,g 3) h (1)4·g 4 g (1)5(h 5·g 6)g (1)7(a 1·g 8)g (1)9g 10b 1⊗(h 2g 2)(2)⊗X h (2)4,g (2)5 (h 5·g (2)7 a 2·g (2)9g10b 2=Σh 1g 1⊗X (h 2,g 2) h (1)3·g 3 g (1)4 h (1)4·g 5 g (1)6(h 5·g 7)g (1)8(a 1·g 9)g (1)10g11b 1⊗h (2)3g (2)4⊗X h (2)4,g (2)6 h 5·g (2)8 a 2·g (2)10 g11b 2=Σh 1g 1⊗X (h 2,g 2) h (1)3·g 3 h (1)4·g 4 h (1)4·g 4 g (1)5(h 5·g 6)g (1)7(a 1·g 8)g (1)9g (1)10g11b 11Hopf113⊗h(2)3g(2)5⊗Xh(2)4,g(2)7h 5·g(2)4a2·g(2)10g 11b2=Σh1g1⊗X(h2,g2)h(1)3·g3(h 5·g5)g(1)6(a1·g7)g(1)8g(1)9g(1)10g 11b1⊗h(2)3g(2)6⊗Xh(2)9,g(2)8(h 5·g(2)9a2·g(2)10g 11b2=Σh1g1⊗X(h2,g2)h(1)3·g3h(1)4·g4(h 5·g5)(a1·g6)g(1)7g(1)8g(1)9g(1)10g 11b1⊗h(2)3g(2)7⊗Xh(2)4,g(2)8h 5·g(2)9a2·g(2)10g 11b2=Σh1g1⊗X(h2,g2)h(1)3h(1)4h 5a1·g3g(1)4g(1)5g(1)6g(1)7g 8b1⊗h(2)3g(2)4⊗Xh(2)4,g(2)5h 5·g(2)6a2·g(2)7g 8b2=Σh1g1⊗X(h2,g2)h(1)3h(1)4h 5a1·g3g(1)4g(1)5g(1)6g 7b1⊗h(2)3g(2)4⊗Xh(2)4,g(2)5(h 5a2)·a(2)6g 7b2=Σh1g1⊗X(h2,g2)h(1)3h 4a1·g3g(1)4g 5b1⊗h231g(2)41⊗Xh(2)32,g(2)42(h 4a2)·g(2)43g 5b2=Σh1⊗h(1)2h 3a1⊗h(2)2⊗h 3a2g1⊗g(1)2g 3b1⊗g(2)2⊗g 3b2=∆(h⊗a)∆(g⊗b).(D)(C),(A),(B),(H⊗A,∆,ε,·,1⊗1)2.1 2.1ψ,Xψ(h)=ε(h)(1⊗1),X(h,l)=ε(h)ε(l),(C),(f),(D)(b)A H-(e)H A-(A1), (A2),(B1),(B2)ε(a·h)=ε(a)ε(h),∆(a·h)=Σa1·h1h(1)2⊗a2·h(2)2,β(1)=1⊗1,β(hg)=Σh(1)g1g(1)2⊗h(2)g(2)2,Σh(1)1(a·h2)⊗h(2)1=Σ(a1·h1)h(1)2⊗h(2)2.(h⊗a)(g⊗b)=Σhg1⊗(a·g2)b,∆(h⊗a)=Σh1⊗h(1)2a1⊗h(2)2⊗a2.ε(h⊗a)=ε(h)ε(a)Hβ[ψ] α[X]A Hβ αA,Smash([8], 3.3).Smash2.2H A A Hα(a⊗h)=a·h=ε(h)a,β(h)=1⊗h,(b)X(h,l)∈Z(A)(A),(e)Σψ(h1)⊗h2=Σψ(h2)⊗h1,114392.1Hβ[ψ] α[X]A(h⊗a)(g⊗b)=Σh1g1⊗X(h2,g2)ab,∆(h⊗a)=Σh1⊗h 3a1⊗h2⊗h 3a2,ε(h⊗a)=ε(h)ε(a).2.3u∈Hom k(H,A)u(1)=1,εu=ε.α:A⊗H→A;α(a⊗h)=Σu(h1)au−1(h2),β:H→A⊗H;β(h)=Σu(h1)u−1(h3)⊗h2,X:H⊗H→A;X(h,k)=Σu(h1k1)u−1(h2)u−1(k2),ψ:H→A⊗A;ψ(h)=Σ(u(h1)⊗u(h2))∆u−1(h3).u−1u() 2.1Hβ[ψ] α[X]A2.2Hβ[ψ] α[X]A H⊗A.2.4Hβ[ψ] α[X]Ai:A→Hβ[ψ] α[X]A;i(a)=1⊗a,j:H→Hβ[ψ] α[X]A;j(h)=h⊗1,p:Hβ[ψ] α[X]A→H;p(h⊗a)=ε(a)h,q:Hβ[ψ] α[X]A→A;q(h⊗a)=ε(h)a.A i→Hβ[ψ] α[X]A p→H Hopf()qi=1,pj=1,q(1)=1, j(1)=1,εq=ε,εj=ε,q(ki(a))=q(k)a,(1⊗j)∆=(p⊗1)∆j.2.2A i→K p→H Hopf()q:K→A; j:H→K qi=1,pj=1,q(1)=1,j(1)=1,εq=ε,εj=ε,(1⊗j)∆=(p⊗1)∆j, q(ki(a))=q(k)a.q∈Hom k(K,A)j∈Hom k(H,K)Hopf K∼=Hβ[ψ] α[X]A.Hβ[ψ] α[X]Aβ:H→A⊗H;β(h)=Σq(k1)q−1(k3)⊗p(k2),p(k)=h,ψ:H→A⊗A;ψ(h)=Σ(q(k1)⊗q(k2))∆q−1(k3),α:A⊗H→A;α(a⊗h)=a·h=Σj−1(h1)i(a)j(h2),X:H⊗H→A;X(h,g)=Σj−1p(k1r1)jp(k2)jp(r2),p(k)=h,p(r)=g.A i(A),a i(a)(a∈A)q−1,j−1q,j()k.a=ki(a),∀a∈A,k∈K,K A-q(ki(a))=q(k)a,∀a∈A,k∈K,q A-εq=ε,q K A-[9]2,K∼=Hβ[ψ] A.β:H→A⊗H;β(h)=Σq(k1)q−1(k3)⊗p(k2),p(k)=h,1Hopf115ψ:H →A ⊗A ;ψ(h )=Σ(q (k 1)⊗q (k 2))∆q −1(k 3),f :K →H β[ψ] A ;f (k )=Σp (k 1)⊗q (k 2).ff()ff :H β[ψ] H →K ;f (h ⊗a )=Σk 1i q −1(k 2)a,p (k )=hρ=(p ⊗1)∆:K →H ⊗K ,KH -(1⊗j )∆=(p ⊗1)∆j ,j :H →KH -jKH -K ∼=H α[X ]A[2],iHopfA i (A )α:A ⊗H →A ;α(a ⊗h )=a ·h =Σj −1(h 1)i (a )j (h 2),X :H ⊗H ⊗A ;X (h,g )=Σj −1p (k 1r 1)jp (k 1)jp (r 2),h =p (k ),g =p (r ).Φ:H α[X ]A →K ;Φ(h ⊗a )=j (h )i (a )Φ()Φ ,Φ (k )=Σp (k 1)⊗j −1(p (k 2))k 3.f Φ(h ⊗a )=f (j (h )i (a ))=Σp ((j (h )i (a ))1)⊗q ((j (h )i (a ))2)=Σp ((j (h ))1i (a 1))⊗q ((j (h ))2i (a 2))=Σp ((j (h ))1)pi (a 1)⊗q ((j (h ))2)qi (a 2)=Σp ((j (h ))1)ε(a 1)⊗q ((j (h ))2)a 2=Σp ((j (h ))1)⊗q ((j (h ))2)a =Σh 1⊗qj (h 2)a ((1⊗j )∆=(p ⊗1)∆j )=h ⊗a.f Φ=1,f =Φ,Φ =f .f =Φk =Σjp (k 1)iq (k 2),∀k ∈K .Φ =fΣp (k 1)⊗iq (k 2)=Σp (k 1)⊗j −1(p (k 2))k 3,∀k ∈K .ε⊗1iq (k )=Σj −1(p (k 1))k 2,f (k )f (g )=Σ(p (k 1)⊗q (k 2))(p (g 1)⊗q (g 2)),∀k,g ∈K=Σp (k 1)p (g 1)⊗X (p (k 2),p (g 2))(q (k 3),p (g 3))iq (g 4)=Σp (k 1g 1)⊗X (p (k 2),p (g 2))j −1p (g 3)iq (k 4)g 4=Σp (k 1g 1)⊗j −1p (k 2g 2)jp (k 3)iq (k 4)g 4=Σp (k 1g 1)⊗j −1p (k 2g 2)k 3g 3=Σp (k 1g 1)⊗iq (k 2g 2)=f (kg ),f (1)=p (1)⊗q (1)=1⊗1.ffHopfHopfK ∼=H β[ψ] α[X ]A .116392.1A i→K p→H Hopf q:K→Aj:H→K qi=1,pj=1,q(1)=1,εj=ε,(1⊗j)∆=(p⊗1)∆j,q(ki(a))=q(k)a (∀a∈A,k∈K).Hopf K∼=Hβ αA,Hβ αA Smashβ(h)=Σq(k1)sq(k3)⊗p(k2),p(k)=h,α(a⊗h)=a·h=Σjsh1i(a)j(h2).A i(A)q jψ,X2.1SmashH,A Hopf u∈Hom k(H,A)u−1=v.u(1)=1,εu=ε.ψ,ϕH A⊗A X,σH⊗H AX(h,g)=Σu(h1g1)σ(h2,g2)v(h3)v(g3),ψ(h)=Σ(u(h1)⊗u(h2))ϕ(h3)∆v(h4).α,βα(a⊗h)=a·h=Σu(h1)av(h2),β(h)=Σu(h1)v(h3)⊗h2.α ,βα (a⊗h)=ε(h)a,β (h)=1⊗h.2.3H,A Hopfα,β,ψ,X,α ,β ,ϕ,σHβ[ψ] α[X]AHβ [ϕ] α [σ]A Hβ[ψ] α[X]A∼=Hβ [ϕ] α [σ]A.2.32.2H,A Hopf u∈Hom k(H,A)εu=ε,u(1)=1.ψ(h)=Σ(u(h1)⊗u(h2))∆u−1(h3),X(h,g)=Σu(h1g1)u−1(h2)u−1(g2),∀h,g∈H.Hβ[ψ] α[X]A∼=H⊗A.2.3ϕ,σ2.3H,A,u 2.2ϕ(h)=Σu−1(h2)⊗u−1(h1)∆u(h3),σ(h,g)=Σu−1(h1g1)u(g2)u(h2),∀h,g∈H.Hβ αA∼=Hβ [ϕ] α [σ]A,Hβ [ϕ] α [σ]A∼=H⊗A u α ,β1Hopf117[1]Doi,Y.,On the structure of relative Hopf module,Comm.Algebra,11(1983),243–255.[2]Doi,Y.and Takeuchi,M.,Cleft comodule algebras for a bialgebra,Comm.Algebra,14(1986),801–817.[3]Doi,Y.,Equivalent crossed product for a Hopf algebra,Comm.Algebra,17(1989),3053–3085.[4]Blattner,R.J.and Montgomery,S.,Crossed products and Galois extensions of Hopf algebras,Pacific,J.Math.,137(1989),37–54.[5]Molnar,R.K.,Semi-direct products of Hopf algebras,J.Algebra,47(1977),29–51.[6]Blattner R.J.,Cohen,M.and Montgomery,S.,Crossed products and inner action of Hopf algebras,Trans.A.M.S.,298(1986),671–710.[7]Majid,S.,More examples of bicrossproduct and double crossproduct Hopf algebra,Isr.J.Math.,72(1990),133–148.[8]Majid,S.,Physics for algebraists,non-commutative and non-cocommutative Hopf algebra by a bicrossprod-uct construction,J.Algebra,130(1990),17–64.[9]H-38(1993),1449–1452.The Bicrossed Products of Hopf AlgebrasLiu Guilong(Department of Mathematics,China University of Geosciences,Beijing100083,China)Abstract:The purpose of this paper is to begin to lay the foundation of bicrossed products of Hopf algebra.The theory is motivated by asking that crossed product and crossed coproductfit together to form a bialgebra.It is the further generalization of bismash product of Hopf algebra. We investigate the basic properties of these notions and give the exact sequence characterization of bicrossed product.We will see that any bicrossed product Hβ[ψ] α[X]A with weakly inner action and inner coaction is isomorphic to a bicrossed product Hβ [ϕ] α [σ]A with trivial action α and trivial coactionβ .Keywords:crossed coproduct,exact sequence of Hopf algebra,bicrossed product。