The minimum dilatation of pseudo-Anosov 5-braids
The minimum dilatation of pseudo-Anosov 5-braids is shown to be the largest zero $λ_5 \approx 1.72208$ of $x^4 - x^3 - x^2 - x + 1$ which is attained by $σ_1σ_2σ_3σ_4σ_1σ_2$.
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arXiv subjects
Won Taek Song
Publications and source records attributed to Won Taek Song.
The kernel of $Burau(4) \otimes Z_p$ is all pseudo-Anosov
We show that the kernel of $Burau(4) \otimes Z_p$, the reduced Burau representation with coefficients in $Z_p$ of the 4-braid group $B_4$, consists only of pseudo-Anosov braids.
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The Lawrence--Krammer representation is unitary
We show that the Lawrence--Krammer representation is unitary. We explicitly present the non-singular matrix representing the sesquilinear pairing invariant under the action. We show that reversing the orientation of a braid is equivalent to the transposition of its Lawrence--Krammer matrix followed by a certain conjugation. As corollaries it is shown that the characteristic polynomial of the Lawrence--Krammer matrix is invariant under substitution of its variables with their inverses up to multiplication by units, and is not a complete conjugacy invariant for braids.
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