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Evaluations of the twisted Alexander polynomials of 2-bridge knots at $pm 1$

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 Added by Mikami Hirasawa
 Publication date 2008
  fields
and research's language is English




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Let $H(p)$ be the set of 2-bridge knots $K$ whose group $G$ is mapped onto a non-trivial free product, $Z/2 * Z/p$, $p$ being odd. Then there is an algebraic integer $s_0$ such that for any $K$ in $H(p)$, $G$ has a parabolic representation $rho$ into $SL(2, Z[s_0]) subset SL(2,C)$. Let $Delta(t)$ be the twisted Alexander polynomial associated to $rho$. Then we prove that for any $K$ in $H(p)$, $Delta(1)=-2s_0^{-1}$ and $Delta(-1)=-2s_0^{-1}mu^2$, where $s_0^{-1}, mu in Z[s_0]$. The number $mu$ can be recursively evaluated.



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In this paper we show that the twisted Alexander polynomial associated to a parabolic representation determines fiberedness and genus of a wide class of 2-bridge knots. As a corollary we give an affirmative answer to a conjecture of Dunfield, Friedl and Jackson for infinitely many hyperbolic knots.
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