A129769 Exponents m(i) for exceptional groups with best guesses for E7 1/2 and E9 added (there is a problem with the dimension of E9 as no sum of odd numbers will equal the 484, I get 483): triangular sequence is: A1,G2,F4,E6,E7 E7 1/2,E8,E9.

1, 1, 5, 1, 5, 7, 11, 1, 4, 5, 7, 8, 11, 1, 5, 7, 9, 11, 13, 17, 1, 6, 9, 11, 13, 15, 17, 19, 1, 7, 11, 13, 17, 19, 23, 29, 1, 11, 17, 19, 23, 29, 31, 51, 55

Offset

1,3

Comments

Betti number row sums: Table[Apply[Plus, CoefficientList[Expand[Product[(1 + t^(2*a[i][[n]] + 1)), {n, 1, Length[a[i]]}]], t]], {i, 0, 7}] {2, 4, 16, 64, 128, 256, 256, 512} Group dimensions sums: b[n_] = 2*a[n] + 1 Table[Apply[Plus, b[n]], {n, 0, 7}] {3, 14, 52, 78, 133, 190, 248, 483}.

From these exponents it is possible to get Poincaré polynomial estimates for the new E7 1/2 and E8 that best fit the pattern of the known exponents.

References

J. M. Landsberg, The sextonions and E_{7 1/2} (with L.Manivel) (Advances in Math 201(2006) p143 - 179) page 22; J. M. Landsberg, http://www.math.tamu.edu/~jml/LMsexpub.pdf: The sextonions and E_{7 1/2}

Armand Borel's Essays in History of Lie Groups and Algebraic Groups: gives G2 Poincaré polynomial, History of Mathematics, V. 21; http://www.amazon.com/Essays-History-Groups-Algebraic-Mathematics/dp/0821802887/ref=pd_rhf_p_3/104-0029617-0633535

Links

Table of n, a(n) for n=1..45.

Formula

a(0) = {1}; a(1) = {1, 5}; a(2) = {1, 5, 7, 11}; a(3) = {1, 4, 5, 7, 8, 11}; a(4) = {1, 5, 7, 9, 11, 13, 17}; a(5) = {1, 6, 9, 11, 13, 15, 17, 19}; a(6) = {1, 7, 11, 13, 17, 19, 23, 29}; a(7) = {1, 11, 17, 19, 23, 29, 31, 51, 55};

Mathematica

a[0] = {1}; a[1] = {1, 5}; a[2] = {1, 5, 7, 11}; a[3] = {1, 4, 5, 7, 8, 11}; a[4] = {1, 5, 7, 9, 11, 13, 17}; a[5] = {1, 6, 9, 11, 13, 15, 17, 19}; a[6] = {1, 7, 11, 13, 17, 19, 23, 29}; a[7] = {1, 11, 17, 19, 23, 29, 31, 51, 55};

Crossrefs

Cf. A005556, A005763, A005776.

Sequence in context: A062176 A338167 A372958 * A129766 A120283 A103986

Adjacent sequences: A129766 A129767 A129768 * A129770 A129771 A129772

Keyword

nonn,uned

Author

Roger L. Bagula, May 16 2007

Status

approved