"호프 대수(Hopf algebra)"의 두 판 사이의 차이

수학노트
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(피타고라스님이 이 페이지의 위치를 <a href="/pages/12529252">양자군 (quantum group)</a>페이지로 이동하였습니다.)
53번째 줄: 53번째 줄:
 
** comultiplication and counit are a ring maps
 
** comultiplication and counit are a ring maps
 
** multiplication and unit are a coring maps
 
** multiplication and unit are a coring maps
** antipode <math>\mu \circ (\operatorname{id}\otimes S) \circ \Delta = \mu \circ (S\otimes \operatorname{id}) \circ \Delta=1 \circ \epsilon</math>
+
** antipode <math>\mu \circ (\operatorname{id}\otimes S) \circ \Delta = \mu \circ (S\otimes \operatorname{id}) \circ \Delta=1 \circ \epsilon</math>, 많은 경우는 antihomomorphism 즉, <math>S(ab)=S(b)S(a)</math>
  
 
 
 
 
67번째 줄: 67번째 줄:
 
* one wants to have the following H-modules <math>V\otimes W</math> and <math>V^{*}</math>
 
* one wants to have the following H-modules <math>V\otimes W</math> and <math>V^{*}</math>
 
* For Hopf algebra, we can construct them as H-modules
 
* For Hopf algebra, we can construct them as H-modules
 +
* counit - trivial representations
 
*  tensor product<br><math>a.(v\otimes w)= \Delta(a)(v\otimes w)</math><br>
 
*  tensor product<br><math>a.(v\otimes w)= \Delta(a)(v\otimes w)</math><br>
 
*  dual representation<br> For <math>f\in V^{*}</math>, <math>(a.f)(v)= f(S(a).v)</math><br>
 
*  dual representation<br> For <math>f\in V^{*}</math>, <math>(a.f)(v)= f(S(a).v)</math><br>
 
+
* the category of representations has a monoidal structure with duals
 
 
  
 
 
 
 
78번째 줄: 78번째 줄:
 
<h5>예 : group ring</h5>
 
<h5>예 : group ring</h5>
  
<math>H=\mathbb{F}G</math> : group algebra of G over F
+
* <math>H=\mathbb{F}G</math> : group algebra of G over F
 
 
 
*  multiplication and identity element<br><math>m : \mathbb Z[G]\otimes \mathbb Z[G] \to \mathbb Z[G]</math><br>
 
*  multiplication and identity element<br><math>m : \mathbb Z[G]\otimes \mathbb Z[G] \to \mathbb Z[G]</math><br>
 
*  comultiplication<br><math>\Delta : \mathbb Z[G] \to \mathbb Z[G]\otimes \mathbb Z[G] </math><br><math>g \mapsto g\otimes g</math><br>
 
*  comultiplication<br><math>\Delta : \mathbb Z[G] \to \mathbb Z[G]\otimes \mathbb Z[G] </math><br><math>g \mapsto g\otimes g</math><br>
91번째 줄: 90번째 줄:
 
<h5>예 : UEA</h5>
 
<h5>예 : UEA</h5>
  
* simple Lie algebra g
+
* simple Lie algebra <math>\mathfrak{g}</math>
 
* <math>U(\mathfrak{g})</math>
 
* <math>U(\mathfrak{g})</math>
 
*  comultiplication (this explains why the tensor product of <math>U(\mathfrak{g})</math>-modules is defined as known)<br><math>\Delta : U(\mathfrak{g}) \to U(\mathfrak{g})\otimes U(\mathfrak{g}) </math><br><math>\Delta(x) =x\otimes 1+ 1 \otimes x</math> for <math>x \in \mathfrak{g}</math><br><math>\Delta(1)=1\otimes 1</math><br>
 
*  comultiplication (this explains why the tensor product of <math>U(\mathfrak{g})</math>-modules is defined as known)<br><math>\Delta : U(\mathfrak{g}) \to U(\mathfrak{g})\otimes U(\mathfrak{g}) </math><br><math>\Delta(x) =x\otimes 1+ 1 \otimes x</math> for <math>x \in \mathfrak{g}</math><br><math>\Delta(1)=1\otimes 1</math><br>
122번째 줄: 121번째 줄:
 
<h5>메모</h5>
 
<h5>메모</h5>
  
 
+
* [http://sbseminar.wordpress.com/2007/10/07/group-hopf-algebra/ Group = Hopf algebra] , Scott Carnahan, Secret Blogging Seminar,  October 7, 2007
 +
* http://mathoverflow.net/questions/101739/is-there-any-progress-on-the-theory-in-the-paper-geometric-methods-in-representa<br>
  
 
* Math Overflow http://mathoverflow.net/search?q=
 
* Math Overflow http://mathoverflow.net/search?q=

2012년 8월 26일 (일) 06:22 판

이 항목의 수학노트 원문주소

 

 

개요
  • 호프 대수(Hopf algebra) = bi-algebra with an antipoe
  • '군(group)' (군론(group theory) 항목 참조) 개념의 일반화
  • 양자군의 이론에서 중요한 역할
    • 양자군(quantum group) = non co-commutative quasi-triangular Hopf algebra

 

 

군(group) 의 정의 : abstract nonsense
  • 군의 정의를 abstract nonsense를 사용하여 표현하기
  • a group is a set \(G&bg=ffffff&fg=000000&s=0\) equipped with
    • a multiplication map \(\mu: G \otimes G \to G\)
    • an inversion map \(S: G \to G\)
    • an identity element \(1:+*+\to+G&bg=ffffff&fg=000000&s=0\), where \(*&bg=ffffff&fg=000000&s=0\) is a one point set
    • \(\epsilon:+G+\to+*&bg=ffffff&fg=000000&s=0\)  (trivial representation, counit)
    • \(\Delta: G \to G \otimes G\), diagonal map: \(g \mapsto g\otimes g\)
  • 일반적으로 군을 정의할 때 드러나지 않는 \(\epsilon:+G+\to+*&bg=ffffff&fg=000000&s=0\) , \(\Delta:+G+\to+G+\times+G&bg=ffffff&fg=000000&s=0\)를 도입함으로써, 군을 abstract nonsense 만으로 표현할 수 있게 된다
  • 결합법칙
    \(\mu \circ (\mu \otimes \operatorname{id})=\mu \circ (\operatorname{id}\otimes \mu)\)
  • 역원에 대한 조건 (원소에 그 역원을 곱하면 항등원을 얻는다)
    \(\mu \circ (\operatorname{id}\otimes S) \circ \Delta = \mu \circ (S\otimes \operatorname{id}) \circ \Delta=1 \circ \epsilon\), i.e., multiplying an element with its inverse yields the unit.

 

 

호프 대수(Hopf algebra) 의 정의
  • Hopf algebra = an algebra with unit and three maps = bialgebra with an antipode
  • Given a commutative ring \(R&bg=ffffff&fg=000000&s=0\), a Hopf algebra over \(R&bg=ffffff&fg=000000&s=0\) is a six-tuple \((G, \mu, 1, S, \epsilon, \Delta)\),
    • \(G&bg=ffffff&fg=000000&s=0\)is an \(R&bg=ffffff&fg=000000&s=0\)-module
    • \(\mu: G \otimes_R G \to G\) is a multiplication map
    • \(1:+R+\to+G&bg=ffffff&fg=000000&s=0\) is a unit
    • \(S: G \to G\) is called the antipode
    • \(\epsilon:+G+\to+R&bg=ffffff&fg=000000&s=0\) is a counit
    • \(\Delta:+G+\to+G+\otimes_R+G&bg=ffffff&fg=000000&s=0\) is called comultiplication.

 

  • These are required to satisfy relations
    • \((G,\mu,1)\)  ring
    • \((G,\Delta,\epsilon)\) coring (just turn all the previous arrows around)
    • comultiplication and counit are a ring maps
    • multiplication and unit are a coring maps
    • antipode \(\mu \circ (\operatorname{id}\otimes S) \circ \Delta = \mu \circ (S\otimes \operatorname{id}) \circ \Delta=1 \circ \epsilon\), 많은 경우는 antihomomorphism 즉, \(S(ab)=S(b)S(a)\)

 

 

표현론에서 유용한 점

 

  • H : Hopf algebra
  • V,W : H-modules
  • one wants to have the following H-modules \(V\otimes W\) and \(V^{*}\)
  • For Hopf algebra, we can construct them as H-modules
  • counit - trivial representations
  • tensor product
    \(a.(v\otimes w)= \Delta(a)(v\otimes w)\)
  • dual representation
    For \(f\in V^{*}\), \((a.f)(v)= f(S(a).v)\)
  • the category of representations has a monoidal structure with duals

 

 

예 : group ring
  • \(H=\mathbb{F}G\) : group algebra of G over F
  • multiplication and identity element
    \(m : \mathbb Z[G]\otimes \mathbb Z[G] \to \mathbb Z[G]\)
  • comultiplication
    \(\Delta : \mathbb Z[G] \to \mathbb Z[G]\otimes \mathbb Z[G] \)
    \(g \mapsto g\otimes g\)
  • counit
    \(\epsilon(g)=1\)
  • antipode
    \(S(g)=g^{-1}\)

 

 

예 : UEA
  • simple Lie algebra \(\mathfrak{g}\)
  • \(U(\mathfrak{g})\)
  • comultiplication (this explains why the tensor product of \(U(\mathfrak{g})\)-modules is defined as known)
    \(\Delta : U(\mathfrak{g}) \to U(\mathfrak{g})\otimes U(\mathfrak{g}) \)
    \(\Delta(x) =x\otimes 1+ 1 \otimes x\) for \(x \in \mathfrak{g}\)
    \(\Delta(1)=1\otimes 1\)

 

 

 

 

 

역사

 

 

 

메모

 

 

관련된 항목들

 

 

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