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BLM/Ho Polynomial


A 1-variable unoriented knot polynomial Q(x). It satisfies

 Q_(unknot)=1
(1)

and the skein relationship

 Q_(L_+)+Q_(L_-)=x(Q_(L_0)+Q_(L_infty)).
(2)

It also satisfies

 Q_(L_1#L_2)=Q_(L_1)Q_(L_2),
(3)

where # is the knot sum and

 Q_(L^*)=Q_L,
(4)

where L^* is the mirror image of L. The BLM/Ho polynomials of mutant knots are also identical. Brandt et al. (1986) give a number of interesting properties. For any link L with >=2 components, Q_L-1 is divisible by 2(x-1). If L has c components, then the lowest power of x in Q_L(x) is 1-c, and

 lim_(x->0)x^(c-1)Q_L(x)=lim_((l,m)->(1,0))(-m)^(c-1)P_L(l,m),
(5)

where P_L is the HOMFLY polynomial. Also, the degree of Q_L is less than the link crossing number of L. If L is a 2-bridge knot, then

 Q_L(z)=2z^(-1)V_L(t)V_L(t^(-1)+1-2z^(-1)),
(6)

where z=-t-t^(-1) (Kanenobu and Sumi 1993).

The polynomial was subsequently extended to the 2-variable Kauffman polynomial F, which satisfies

 Q(x)=F(1,x).
(7)

Brandt et al. (1986) give a listing of Q polynomials for knots up to 8 crossings and links up to 6 crossings.


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References

Brandt, R. D.; Lickorish, W. B. R.; and Millett, K. C. "A Polynomial Invariant for Unoriented Knots and Links." Invent. Math. 84, 563-573, 1986.Ho, C. F. "A New Polynomial for Knots and Links--Preliminary Report." Abstracts Amer. Math. Soc. 6, 300, 1985.Kanenobu, T. and Sumi, T. "Polynomial Invariants of 2-Bridge Knots through 22-Crossings." Math. Comput. 60, 771-778 and S17-S28, 1993.Stoimenow, A. "Brandt-Lickorish-Millett-Ho Polynomials." http://www.ms.u-tokyo.ac.jp/~stoimeno/ptab/blmh10.html.

Referenced on Wolfram|Alpha

BLM/Ho Polynomial

Cite this as:

Weisstein, Eric W. "BLM/Ho Polynomial." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/BLMHoPolynomial.html

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