■単純リー環を使った面数数え上げ(その27)

【1】Cnのボロノイ細胞の要素数

  fk^(n)=2^k+1(n,k+1)+2^k+2(n−k−1)(n,k+1)

=2^k+1(2n−2k−1)(n,k+1)

  fk^(n-1)=2^k+1(2n−2k−3)(n−1,k+1)

  fk-1^(n-1)=2^k(2n−2k−1)(n−1,k)

  (n−1,k+1)+(n−1,k)=(n,k+1)

  fk^(n)=2^k+1(2n−2k−1)(n,k+1)

=2^k+1(2n−2k−1){(n−1,k+1)+(n−1,k)}

=2^k+1(2n−2k−1)(n−1,k+1)+2^k+1(2n−2k−1)(n−1,k)

  2^k+1(2n−2k−1)=2^k+1(2n−2k−3)+2^k+2

  fk^(n)=2^k+1(2n−2k−3)(n−1,k+1)+2^k+2(n−1,k+1)+2^k+1(2n−2k−1)(n−1,k)

=fk^(n-1)+2^k+2(n−1,k+1)+2fk-1^(n-1)

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 3次元:(f0,f1,f2)=(12,24,14)→存在(010)

 4次元:(f0,f1,f2,f3)=(24,96,96,24)→存在(0100)

 5次元:(f0,f1,f2,f3,f4)=(40,240,400,240,42)→存在(01000)

 6次元:(f0,f1,f2,f3,f4,f5)=(60,480,1120,1200,576,76)→存在(010000)

2≦k≦n−2

n=4,k=2: 96≠14+16+2・24

n=5,k=2: 400≠96+16・4+2・96

n=5,k=3: 240≠24+32+2・96

 まったく,NGである.

n=6,k=2: 1120≠400+16・10+2・240

n=6,k=3: 1200=240+32・5+2・400

n=6,k=4: 576≠42+64+2・240

 等号が成り立つ範囲はかなり狭いようである.

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