Proceedings of the London Mathematical Society Advance Access originally published online on November 24, 2007
Proceedings of the London Mathematical Society 2008 96(3):669-696; doi:10.1112/plms/pdm044
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© 2007 London Mathematical Society
-rational cycles for degree-2 rational maps having an automorphism
University of Southern California
Department of Mathematics
3620 South Vermont Avenue
KAP 108
Los Angeles
CA 90089-2532
USA
Received 11 February 2007. Revision received 10 October 2007.
Let
:
1
1 be a rational map of degree d = 2 defined over
and assume that f–1°
° f =
for exactly one nontrivial f
PGL2 (
). We describe families of such maps that have
-rational periodic points of period 1, 2, and 4, and we prove that no such map has a
-rational periodic point of exact period 3. We give a complete description of the
-rational preperiodic points with period at most 4 and show in particular that there are at most 12 such points.
2000 Mathematics Subject Classification 11G99, 14G25.