# Bugs

From Knot Atlas

- The
`PD`

notation used by`KnotTheory``

is inadequate when a knot diagram contains kinks. For example, there is no way to tell the orientation of`PD[X[1,1,2,2]]`

. You can define braids with kinks, though:`Kink = BR[2, {1}]`

. All knot invariants defined for braid representatives will be correctly evaluated. For example, the previously defined`Kink`

will of course have the same invariants as the unknot. However, don't try to transform the braid into a planar diagram (`PD[BR[2, {1}]]`

), as mathematica might hang up on that.

- Many knot invariants (including
`Jones`

) do not understand the (artificial but necessary)`PD`

construct "`Loop`

".

- Mathematica 9 defines its own tensor product, which causes bugs with the QuantumGroups` package. Stick with Mathematica 7 or 8 until Scott has it fixed.

- For some unexplicable bugs (in Mathematica 8 only?), it appears helpful to state the "context" explicitly, e.g.
`KnotTheory`BR`

instead of`BR`

, or`MirrorTrefoil = PD[KnotTheory`X[1, 5, 2, 4], KnotTheory`X[3, 1, 4, 6], KnotTheory`X[5, 3, 6, 2]]`

instead of`MirrorTrefoil = PD[X[1, 5, 2, 4], X[3, 1, 4, 6], X[5, 3, 6, 2]]`

.