ScalingStacks

6.1 Some elementary properties

Pick an oriented link LL and a component L′L^{\prime} of L.L. Let L0L_{0} be LL with the orientation of L′L^{\prime} reversed and let ll be the linking number of L′L^{\prime} and L∖L′.L\setminus L^{\prime}. Fixing a plane diagram DD of LL, we count ll as half the number of double intersection points in DD of L′L^{\prime} with L∖L′L\setminus L^{\prime} with weights +1+1 or −1-1 according to the following convention

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Denote by D0D_{0} the diagram DD with the reversed orientation of L′.L^{\prime}. Since D0D_{0} and DD are the same as unoriented diagrams, C¯​(D0)=C¯​(D).\overline{C}(D_{0})=\overline{C}(D). Also

x⁡(D0)=x⁡(D)−2​l,y⁡(D0)=y⁡(D)+2​lx(D_{0})=x(D)-2l,y(D_{0})=y(D)+2l (134)

We obtain

0PLU

Proposition 22 For L,L0L,L_{0} as above, there is an equality

Hi​(L0)=Hi+2​l​(L)​{2​l}H^{i}(L_{0})=H^{i+2l}(L)\{2l\} (135)

of isomorphism classes of graded RR-modules.

Let K,K1K,K_{1} be oriented knots and (−K)(-K) be KK with orientation reversed. In a similar fashion we deduce

0PLV

Proposition 23 There is an equality

Hi​(K​#​K1)=Hi​((−K)​#​K1)H^{i}(K\#K_{1})=H^{i}((-K)\#K_{1}) (136)

of isomorphism classes of graded RR-modules.

Let DD be a diagram of an oriented link LL and denote by cm⁡(L){\mathrm{cm}}(L) the number of connected components of L.L. Then it is easy to see that Cji​(D)=0C^{i}_{j}(D)=0 if parities of jj and cm⁡(L){\mathrm{cm}}(L) differ. This observation implies

0PLW

Proposition 24 For an oriented link LL

Hi,j​(L)=0H^{i,j}(L)=0 (137)

if j+1≡cm​(L)​(mod ​2).j+1\equiv{\mathrm{cm}}(L)(\mbox{mod }2).

Original mathematics by the credited authors. Source collection and HTML conversion remain in progress.

Mikhail Khovanov

Original source: arXiv:math/9908171v2