This paper describes a family of pseudo-Anosov braids with small dilatation. The smallest dilatations occurring for braids with 3,4 and 5 strands appear in this family. A pseudo-Anosov braid with 2g + 1 strands determines a hyperelliptic mapping class with the same dilatation on a genus–g surface. Penner showed that logarithms of least dilatations of pseudo-Anosov maps on a genus–g surface grow asymptotically with the genus like 1∕g, and gave explicit examples of mapping classes with dilatations bounded above by log11∕g. Bauer later improved this bound to log6∕g. The braids in this paper give rise to mapping classes with dilatations bounded above by log(2 + 3)∕g. They show that least dilatations for hyperelliptic mapping classes have the same asymptotic behavior as for general mapping classes on genus–g surfaces.
Hironaka, Eriko  1 ; Kin, Eiko  2
@article{10_2140_agt_2006_6_699,
author = {Hironaka, Eriko and Kin, Eiko},
title = {A family of {pseudo-Anosov} braids with small dilatation},
journal = {Algebraic and Geometric Topology},
pages = {699--738},
year = {2006},
volume = {6},
number = {2},
doi = {10.2140/agt.2006.6.699},
url = {http://geodesic.mathdoc.fr/articles/10.2140/agt.2006.6.699/}
}
TY - JOUR AU - Hironaka, Eriko AU - Kin, Eiko TI - A family of pseudo-Anosov braids with small dilatation JO - Algebraic and Geometric Topology PY - 2006 SP - 699 EP - 738 VL - 6 IS - 2 UR - http://geodesic.mathdoc.fr/articles/10.2140/agt.2006.6.699/ DO - 10.2140/agt.2006.6.699 ID - 10_2140_agt_2006_6_699 ER -
Hironaka, Eriko; Kin, Eiko. A family of pseudo-Anosov braids with small dilatation. Algebraic and Geometric Topology, Tome 6 (2006) no. 2, pp. 699-738. doi: 10.2140/agt.2006.6.699
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