Finite dimensional representations of Sl(2)

수학노트
http://bomber0.myid.net/ (토론)님의 2010년 4월 4일 (일) 19:31 판
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introduction

 

 

 

character formula
  • Weyl-Kac formula
    \(ch(V)={\sum_{w\in W} (-1)^{\ell(w)}w(e^{\lambda+\rho}) \over e^{\rho}\prod_{\alpha>0}(1-e^{-\alpha})}\)
  • for trivial representation, we get denominator identity
    \({\sum_{w\in W} (-1)^{\ell(w)}w(e^{\rho}) = e^{\rho}\prod_{\alpha>0}(1-e^{-\alpha})^{m_{\alpha}}}\)

 

 

Chebyshev polynomial
  • \(U_{n+1}(x) & = 2xU_n(x) - U_{n-1}(x)\)
  • Define \(w^{2(2k+3)}=1\) and \(z=w+w^{-1}\)

 

\(p_i(z)=\frac{w^{i+1}-w^{-i-1}}{w-w^{-1}}\) for \( i=1,\cdots, k\)

 

 

  • \(p_{0}(z)=1\)
  • \(p_{1}(z)=z\)
  • \(p_i(z)^2=1+p_{i-1}(z)p_{i+1}(z)\)

 

 

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