New York Journal of Mathematics
Volume 6 (2000) 107-117

  

John C. O'Neill and Edward C. Turner

Test Elements and the Retract Theorem in Hyperbolic Groups


Published: July 21, 2000
Keywords: test words, test elements, endomorphisms, automorphisms, hyperbolic groups
Subject: 20E36, 20F232

Abstract
We prove that in many, perhaps all, torsion free hyperbolic groups, test elements are precisely those elements not contained in proper retracts. We also show that all Fuchsian groups have this property. Finally, we show that all surface groups except Z×Z have test elements.

Author information

John C. O'Neill:
DFMS, United States Air Force Academy, CO 80840-6252
John.Oneill@usafa.af.mil
http://www.usafa.af.mil/dfms/people/oneill.htm

Edward C. Turner:
Dept. of Math., University at Albany, Albany, NY 12222
ted@math.albany.edu
http://nyjm.albany.edu:8000/~ted